Oxygen sensor and preparation method therefor, sensing element and preparation method therefor, engine, and vehicle

Abstract

An oxygen sensor (100a), comprising a first electrolyte layer (11a) and a second electrolyte layer (12a) which are stacked, wherein a detection cavity (30a) is formed in the second electrolyte layer (12a). The oxygen sensor (100a) further comprises a diffusion barrier structure (20a), wherein the diffusion barrier structure (20a) at least partially passes through the first electrolyte layer (11a), and the diffusion barrier structure (20a) is in communication with the detection cavity (30a). The side of the diffusion barrier structure (20a) distant from the second electrolyte layer (12a) has a first end face (21), and the first end face (21) is flush with or protrudes from the surface of the first electrolyte layer (11a) facing away from the second electrolyte layer (12a).

Description

Oxygen sensor, sensing element and manufacturing method thereof, engine, and vehicle

[0001] This application claims priority to the Chinese patent application with application number 202410128483.7 filed with the China Patent Office on January 29, 2024, the Chinese patent application with application number 202410135127.8 filed with the China Patent Office on January 30, 2024, the Chinese patent application with application number 202410129367.7 filed with the China Patent Office on January 29, 2024, and the Chinese patent application with application number 202420202337.X filed with the China Patent Office on January 26, 2024. The entire contents of the above applications are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of sensor technology, and in particular to an oxygen sensor, a sensor element and a preparation method thereof, an engine, and a vehicle. Background Art

[0003] Oxygen sensors convert the oxygen concentration in a gas to a computer-readable electrical signal, playing a vital role in the automotive, medical, industrial, and environmental monitoring fields. For example, oxygen sensors can be applied to engines to detect the oxygen concentration in engine exhaust. Summary of the Invention

[0004] In the related art, during the lamination process of the oxygen sensor, the gas channel to be measured of the oxygen sensor is easily squeezed and deformed, thereby damaging the diffusion barrier structure, and ultimately affecting the detection accuracy.

[0005] The present application provides an oxygen sensor, which includes: a stacked first electrolyte layer and a second electrolyte layer, wherein a detection cavity is provided in the second electrolyte layer; the oxygen sensor also includes: a diffusion barrier structure, wherein the diffusion barrier structure is at least partially provided through the first electrolyte layer, and the diffusion barrier structure is connected to the detection cavity; wherein the diffusion barrier structure has a first end face on the side away from the second electrolyte layer, and the first end face is flush with or protrudes from the surface of the first electrolyte layer facing away from the second electrolyte layer. By making the first end face of the diffusion barrier structure flush with or protruding from the surface of the first electrolyte layer facing away from the second electrolyte layer, the gas to be measured enters the detection cavity through the diffusion barrier structure. Compared with related technologies, the present application does not need to set up a gas channel to be measured, thereby avoiding the situation where the gas channel to be measured is squeezed and deformed, and also avoids the situation where the diffusion barrier structure is squeezed and damaged by the deformed gas channel, thereby improving detection accuracy.

[0006] The present application also provides a method for preparing an oxygen sensor, the preparation method comprising: forming a detection cavity in the second electrolyte layer; stacking the first electrolyte layer and the second electrolyte layer; forming a diffusion barrier structure that at least partially penetrates the first electrolyte layer; the diffusion barrier structure is connected to the detection cavity; wherein the diffusion barrier structure has a first end face on the side away from the second electrolyte layer, and the first end face is flush with or protrudes from the surface of the first electrolyte layer that faces away from the second electrolyte layer. By making the first end face of the diffusion barrier structure flush with or protrudes from the surface of the first electrolyte layer that faces away from the second electrolyte layer, the gas to be measured enters the detection cavity through the diffusion barrier structure. Compared with related technologies, the present application does not require the provision of a gas channel to be measured, thereby avoiding the situation where the gas channel to be measured is squeezed and deformed, and also avoiding the situation where the diffusion barrier structure is squeezed and damaged by the deformed gas channel, thereby improving detection accuracy.

[0007] The present application also provides another oxygen sensor, comprising: a first electrolyte layer, an electrolyte covering layer, and a second electrolyte layer stacked in sequence; wherein the first electrolyte layer is provided with a first diffusion channel; the electrolyte covering layer is provided with at least one second diffusion channel; and the total cross-sectional area of ​​all the second diffusion channels is smaller than the cross-sectional area of ​​the first diffusion channel; the second electrolyte layer is provided with a diffusion barrier and a detection cavity, the diffusion barrier being connected to the first diffusion channel at least through the second diffusion channel, and the detection cavity being connected to the second diffusion channel at least through the diffusion barrier. By adding an electrolyte covering layer between the first electrolyte layer and the second electrolyte layer, the pressure of the electrolyte covering layer on the diffusion barrier is more evenly distributed during the lamination process of the oxygen sensor, thereby preventing the diffusion barrier from rupturing and improving product yield.

[0008] The present application also provides another method for preparing an oxygen sensor, comprising: forming a first diffusion channel in a first electrolyte layer; forming a diffusion barrier and a detection cavity in a second electrolyte layer; forming at least one second diffusion channel in an electrolyte covering layer; wherein the total cross-sectional area of ​​all the second diffusion channels is substantially smaller than the cross-sectional area of ​​the first diffusion channel; stacking the first electrolyte layer, the electrolyte covering layer, and the second electrolyte layer; wherein the diffusion barrier is connected to the first diffusion channel at least through the second diffusion channel, and the detection cavity is connected to the second diffusion channel at least through the diffusion barrier. By adding an electrolyte covering layer between the first electrolyte layer and the second electrolyte layer, the pressure of the electrolyte covering layer on the diffusion barrier is more evenly distributed during the lamination process of the oxygen sensor, thereby preventing the diffusion barrier from rupturing and improving the product yield.

[0009] The present application also provides a sensing element, comprising the oxygen sensor described above, and a protective layer disposed on at least a portion of the surface of the oxygen sensor, the protective layer comprising approximately 85 wt% to approximately 95 wt% of a ceramic phase and approximately 5 wt% to approximately 15 wt% of a binder phase; the ceramic phase comprising one or both of Al2O3 and ZrO2; and the binder phase being a three-phase melt, wherein a first phase comprises MgO, a second phase comprises SiO2, and a third phase comprises one of CaO, TiO2, or Al2O3. The protective layer comprises the ceramic phase and the binder phase, and the binder phase is sintered with a sintering aid. The sintering aid forms a three-phase coexisting melt at a relatively low temperature, acting as an adhesive within the raw materials of the protective layer, thereby increasing the internal bonding strength of the protective layer and the bonding strength between the protective layer and the oxygen sensor, thereby ensuring a strong bond between the protective layer and the oxygen sensor, making the protective layer less likely to fall off and thereby increasing the service life of the sensing element.

[0010] The present application also provides a method for preparing a sensor element, comprising the following steps: S1, ball milling a mixed ceramic powder, a pore-forming agent, a sintering aid, and a first solvent to obtain a first powder; S2, drying the first powder and sieving it to obtain a second powder; S3, grinding and mixing the second powder with a dispersant, a binder, and a second solvent to obtain a protective layer slurry; S4, coating the protective layer slurry on an oxygen sensor to obtain a sensor element green body; S5, sintering the sensor element green body. The protective layer includes a ceramic phase and a binder phase, and the binder phase is obtained by sintering a sintering aid. The sintering aid forms a molten phase in which three phases coexist at a relatively low temperature, and acts as an adhesive in the raw materials of the protective layer, thereby increasing the internal bonding strength of the protective layer and the bonding strength between the protective layer and the oxygen sensor, thereby ensuring a firm bond between the protective layer and the oxygen sensor, and preventing the protective layer from falling off, thereby increasing the service life of the sensor element.

[0011] The present application also provides another sensing element, the oxygen sensor element comprising the oxygen sensor described above, and a protective layer at least partially covering the oxygen sensor, the protective layer comprising a stacked inner protective layer, an intermediate protective layer, and an outer protective layer; the inner protective layer is close to the oxygen sensor, and the outer protective layer is far from the oxygen sensor; the thermal expansion coefficient of the inner protective layer is α1, the thermal expansion coefficient of the oxygen sensor is α, and α<α1<13×10 -6 ·k -1 By limiting the thermal expansion coefficient of the inner protective layer in the sensor element protective layer, it is greater than the thermal expansion coefficient of the oxygen sensor and less than 13×10 -6 ·k -1 , thereby preventing the oxygen sensor from expanding outward when it heats up and being constrained by the protective layer, avoiding fatigue cracks and ensuring that the protective layer has better stability during the temperature rise stage of the sensor element.

[0012] The present application also provides an engine, which includes: the oxygen sensor described above, and / or the sensing element described above, which can improve stability and oxygen detection accuracy.

[0013] The present application also provides a vehicle, comprising: the oxygen sensor described above, and / or the sensing element described above, and / or the engine described above, which can improve stability and oxygen detection accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] FIG1 is a schematic structural diagram of a wide-range oxygen sensor in which the diffusion barrier unit is “vertically embedded” in the related art.

[0015] FIG2 is a schematic structural diagram of a wide-range oxygen sensor in which the diffusion barrier unit is a “transverse through-type” in the related art.

[0016] FIG3 is a schematic structural diagram of a cross section of an oxygen sensor provided in an embodiment of the present application.

[0017] FIG4 is a schematic structural diagram of a longitudinal section of an oxygen sensor provided in an embodiment of the present application.

[0018] FIG5 is a cross-sectional schematic diagram of another oxygen sensor provided in an embodiment of the present application.

[0019] FIG6 is a schematic cross-sectional view of another oxygen sensor provided in an embodiment of the present application.

[0020] FIG7 is a cross-sectional schematic diagram of another oxygen sensor provided in an embodiment of the present application.

[0021] FIG8 is a schematic diagram of a sensor element provided in an embodiment of the present application.

[0022] FIG9 is a cross-sectional view of a detection portion of a sensor element provided in an embodiment of the present application.

[0023] FIG10 is an electron microscope image of a cross section of the protective layer in Examples (1-3) of the present application.

[0024] FIG11 is an electron microscope image of a cross section of the protective layer in Comparative Example (1-1).

[0025] Figure 12 is an electron microscope image of the cross section of the protective layer in Comparative Example (1-2).

[0026] FIG13 is an electron microscope image of a cross section of the protective layer in Comparative Example (1-4).

[0027] FIG14 is a schematic top view of another sensor element provided in an embodiment of the present application.

[0028] FIG15 is a cross-sectional schematic diagram of another sensor element provided in an embodiment of the present application.

[0029] FIG16 is a partially enlarged view of the protective layer structure of another sensor element provided in an embodiment of the present application.

[0030] FIG17 is a schematic diagram of the structure of an engine provided in an embodiment of the present application;

[0031] FIG18 is a schematic structural diagram of a vehicle provided in an embodiment of the present application. Modes for Carrying Out the Invention

[0032] In the description of this application, unless otherwise specified or limited, the terms "connected," "connect," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and can refer to internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0033] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature includes the first feature being directly above and obliquely above the second feature, with the first feature having a higher horizontal height than the second feature. A first feature being "below," "below," and "below" a second feature includes the first feature being directly below and obliquely below the second feature, with the first feature having a lower horizontal height than the second feature.

[0034] In the description of this embodiment, terms such as "upper," "lower," "left," "right," "front," and "rear" are used to refer to positions or locations based on the positions or locations shown in the accompanying drawings. These terms are intended to facilitate description and simplify operation, and are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used for descriptive purposes only and do not have any special meanings.

[0035] In the structure of a wide-band oxygen sensor, the diffusion barrier unit is a key component that forms the limiting pump current. Referring to Figures 1 and 2, the diffusion barrier unit 2 of a wide-band oxygen sensor can be divided into two categories based on its shape: "vertically embedded" and "transversely penetrating." That is, the diffusion barrier unit 2 primarily includes "vertically embedded" and "transversely penetrating" structures. The transverse direction here refers to the direction parallel to the width of the oxygen sensor, such as the horizontal direction in Figures 1 and 2, which is the transverse direction; the longitudinal direction here refers to the direction perpendicular to the width of the oxygen sensor, such as the vertical direction in Figures 1 and 2, which is the longitudinal direction.

[0036] Referring to Figure 1 , when the diffusion barrier unit 2 adopts a "vertically embedded" structure, a test gas channel 1 is formed above the diffusion barrier unit 2. The test gas passes through the test gas channel 1 and enters the diffusion barrier unit 2. From there, it enters the detection chamber 3, where oxygen content is detected. This design necessitates the formation of the test gas channel 1. This channel 1 can deform when subjected to pressure during the subsequent lamination process, potentially causing uneven compression or shearing of the diffusion barrier unit 2, leading to rupture and impacting detection accuracy.

[0037] Referring to Figure 2, when the diffusion barrier unit 2 adopts a "transverse through-type" structural design, the diffusion barrier unit 2 transversely penetrates the oxygen sensor, that is, the lateral outer edge of the diffusion barrier unit 2 is flush with the lateral outer edge of the oxygen sensor. The gas to be measured enters the diffusion barrier unit 2 through the two sides of the diffusion barrier unit 2, and then enters the detection cavity 3 through the diffusion barrier unit 2, and then the oxygen content is detected. This structural design does not require the formation of a gas channel 1 to be measured. However, because the diffusion barrier unit 2 is screen-printed onto the solid electrolyte layer using a silk-screen screen, its strength is relatively low. In addition, the diffusion barrier unit 2 has no solid electrolyte body as support in the transverse direction. The diffusion barrier unit 2 will directly bear the pressure during the lamination forming process, which will cause the diffusion barrier unit to be compressed longitudinally, thereby changing its overall design structure and even changing its pore structure and morphology, and also reducing its porosity, thereby affecting the entry of the gas to be measured and affecting the detection accuracy.

[0038] It can be seen that the defects brought about by the above two types of structural designs are that the diffusion barrier unit 2 is easily subjected to uneven extrusion and cracks, or the overall structure of the diffusion barrier unit 2 is easily deformed by extrusion, thereby affecting the detection accuracy. To solve the above technical problems, this application provides the following implementation methods.

[0039] The following embodiments of the present invention are described in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments may be combined with each other.

[0040] First, let's introduce the application scenario of the oxygen sensor illustrated in the example of this application. The oxygen sensor is used to measure the oxygen concentration in the gas to be measured. The oxygen sensor can be a wide-band oxygen sensor.

[0041] 3 and 4 , an embodiment of the present application provides an oxygen sensor comprising: a stacked first electrolyte layer 11a and a second electrolyte layer 12a, wherein a detection cavity 30a is provided in the second electrolyte layer 12a; the oxygen sensor further comprises: a diffusion barrier structure 20a, wherein the diffusion barrier structure 20a is at least partially disposed through the first electrolyte layer 11a and is in communication with the detection cavity 30a; wherein the diffusion barrier structure 20a has a first end face 21 on a side away from the second electrolyte layer 12a, and the first end face 21 is flush with or protrudes from a surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a.

[0042] In the above-described scheme, by aligning the first end surface 21 of the diffusion barrier structure 20a with or protruding from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a, the gas to be measured passes through the diffusion barrier structure 20a and enters the detection cavity 30a. Compared to related art, the present application eliminates the need for a gas channel to be measured, thus preventing the gas channel from being squeezed and deformed. It also prevents the diffusion barrier structure 20a from being squeezed and damaged by the deformed gas channel, thereby improving detection accuracy. The following describes each of the above-described structures in detail with reference to the accompanying drawings.

[0043] When the first electrolyte layer 11a and the second electrolyte layer 12a are provided, referring to Figures 3 and 4, the material of the first electrolyte layer 11a can be a solid electrolyte layer. The material of the second electrolyte layer 12a can also be a solid electrolyte layer. The first electrolyte layer 11a has two surfaces facing each other up and down, and the second electrolyte layer 12a has two surfaces facing each other up and down. One surface of the first electrolyte layer 11a is stacked on one surface of the second electrolyte layer 12a, thereby realizing a stacking design of the first electrolyte layer 11a and the second electrolyte layer 12a. The stacking direction of the first electrolyte layer 11a and the second electrolyte layer 12a is perpendicular to the surfaces of the first electrolyte layer 11a and the second electrolyte layer 12a, as shown in Figures 3 and 4, which is the stacking direction of the first electrolyte layer 11a and the second electrolyte layer 12a.

[0044] A detection chamber 30a is provided in the second electrolyte layer 12a. Referring to Figures 3 and 4, the detection chamber 30a is used to allow the gas to be tested to enter in order to detect the oxygen content of the gas to be tested. The shape of the detection chamber 30a may be, for example, but not limited to, a circular chamber, a square chamber, etc. Exemplarily, the detection chamber 30a may pass through two surfaces of the second electrolyte layer 12a that are opposite in the vertical direction. For example, the detection chamber 30a has a first cavity wall 31 and a second cavity wall 32 that are positioned opposite to each other, wherein the first cavity wall 31 may be located on the surface of the first electrolyte layer 11a facing the second electrolyte layer 12a, and the second cavity wall 32 may be located on the surface of other electrolyte layers stacked on the second electrolyte layer 12a. Exemplarily, a third electrolyte layer 13a is stacked on the surface of the second electrolyte layer 12a facing away from the first electrolyte layer 11a, and the second cavity wall 32 is the surface of the third electrolyte layer 13a facing the second electrolyte layer 12a.

[0045] 3 and 4 , when the diffusion barrier structure 20a is provided, the diffusion barrier structure 20a is at least partially provided through the first electrolyte layer 11a, and the diffusion barrier structure 20a is in communication with the detection cavity 30a, so that the gas to be measured enters the detection cavity 30a through the diffusion barrier structure 20a. That is, the diffusion barrier structure 20a needs to be in communication with the outside of the oxygen sensor, so that the gas to be measured can diffuse into the detection cavity 30a through the diffusion barrier structure 20a. Exemplarily, the diffusion barrier structure 20a can be entirely provided through the first electrolyte layer 11a. Exemplarily, a portion of the diffusion barrier structure 20a can be provided through the first electrolyte layer 11a, and another portion can be provided outside the first electrolyte layer 11a. For example, another portion can be provided in the second electrolyte layer 12a, or it can extend to the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a.

[0046] 3 and 4 , the diffusion barrier structure 20a has a first end surface 21 on the side facing away from the second electrolyte layer 12a. That is, the first end surface 21 is the end surface of the diffusion barrier structure 20a facing away from the second electrolyte layer 12a. The first end surface 21 is flush with or protrudes from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a. Referring to FIG3 and 4 , the upper end surface of the diffusion barrier structure 20a is the first end surface 21, and the first end surface 21 is flush with the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a. Of course, in other embodiments, the first end surface 21 of the diffusion barrier structure 20a can also protrude from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a. That is, in FIG3 and 4 , the first end surface 21 is higher than the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a.

[0047] Compared with related technologies, the present application does not require the provision of a channel for the gas to be measured, thus avoiding deformation of the channel for the gas to be measured caused by pressure during lamination or static pressing, and also avoiding the problem of the diffusion barrier structure 20a being broken by shear force from the channel for the gas to be measured or uneven extrusion. In addition, since the diffusion barrier structure 20a is supported by the first electrolyte layer 11a and the second electrolyte layer 12a, the diffusion barrier structure 20a can be prevented from directly bearing the pressure during lamination or static pressing, thereby protecting the overall shape of the diffusion barrier structure 20a to the maximum extent. Therefore, the solution shown in the embodiment of the present application avoids the problems of forming the channel for the gas to be measured and the shape of the channel during the manufacturing process, and also avoids the problem of the diffusion barrier structure 20a being deformed and cracked by uneven extrusion and deformed by pressure. Moreover, the technical solution shown in the present application is simple in structure, which reduces the difficulty of manufacturing. The overall shape and internal pore morphology of the diffusion barrier structure 20a are easy to control, thereby improving the manufacturing yield and detection accuracy of the oxygen sensor.

[0048] Exemplarily, with reference to Figures 3 and 4, the diffusion barrier structure 20a also extends into the detection cavity 30a, that is, part of the structure of the diffusion barrier structure 20a also extends downward into the detection cavity 30a located in the second electrolyte layer 12a, thereby facilitating the introduction of the gas to be measured into the detection cavity 30a. With this arrangement, the detection cavity 30a can be set at any position in the second electrolyte layer 12a. It is only necessary to additionally set a diffusion barrier structure 20a in the second electrolyte layer 12a so that the diffusion barrier structure 20a extends from the first electrolyte layer 11a all the way into the detection cavity 30a. Of course, in other embodiments, the diffusion barrier structure 20a may not extend into the detection cavity 30a. Exemplarily, the diffusion barrier structure 20a may be located only in the first electrolyte layer 11a, and the detection cavity 30a is set at a position exactly opposite the diffusion barrier structure 20a, thereby eliminating the need to extend the diffusion barrier structure 20a into the detection cavity 30a.

[0049] Exemplarily, referring to Figures 3 and 4, the detection chamber 30a has a first chamber wall 31 and a second chamber wall 32 that are positioned opposite each other, wherein the first chamber wall 31 is the surface of the first electrolyte layer 11a facing the second electrolyte layer 12a. The diffusion barrier structure 20a also has a second end face 22, which can be an end face on the diffusion barrier structure 20a that is positioned opposite to the first end face 21. The second end face 22 abuts against the second chamber wall 32 of the detection chamber 30a. Exemplarily, as shown in Figures 3 and 4, the upper chamber wall of the detection chamber 30a is the first chamber wall 31, and the lower chamber wall of the detection chamber 30a is the second chamber wall 32, as shown in Figures 3 and 4, the upper end face of the diffusion barrier structure 20a is the first end face 21, and the lower end face of the diffusion barrier structure 20a is the second end face 22. The diffusion barrier structure 20a extends all the way to the lower wall of the detection chamber 30a and abuts against it. This not only facilitates the installation of the diffusion barrier structure 20a but also increases the contact area between the diffusion barrier structure 20a and the detection chamber 30a, facilitating the entry of the gas to be measured from the diffusion barrier structure 20a into the detection chamber 30a. Of course, in other embodiments, the second end surface 22 of the diffusion barrier structure 20a may not contact the second wall 32 of the detection chamber 30a, i.e., a gap may exist between the two.

[0050] Exemplarily, the thickness of the first electrolyte layer 11a is D1, the thickness of the second electrolyte layer 12a is D2, and the distance between the first end face 21 and the second end face 22 in the stacking direction is D0, then D0 = D1 + D2. The stacking direction is the stacking direction of the first electrolyte layer 11a and the second electrolyte layer 12a, and the stacking direction is parallel to the thickness direction of the first electrolyte layer 11a and the second electrolyte layer 12a. Exemplarily, the vertical direction shown in Figures 3 and 4 is the stacking direction of the first electrolyte layer 11a and the second electrolyte layer 12a, and is also the thickness direction of the first electrolyte layer 11a and the second electrolyte layer 12a. That is, the stacking direction is perpendicular to the surfaces of the first electrolyte layer 11a and the second electrolyte layer 12a. In Figures 3 and 4, the vertical distance between the first end face 21 and the second end face 22 of the diffusion barrier structure 20a (also referred to as the height of the diffusion barrier structure 20a) is equal to the total thickness of the first electrolyte layer 11a and the second electrolyte layer 12a.

[0051] For example, the thickness of the diffusion barrier structure 20a is D0, the thickness of the first electrolyte layer 11a is D1, and the thickness of the second electrolyte layer 12a is D2, thus satisfying the condition D0 = D1 + D2. Referring to Figures 3 and 4, the diffusion barrier structure 20a extends longitudinally from the upper surface of the third electrolyte layer 13a to the upper surface 101 of the oxygen sensor. The thickness here refers to the direction perpendicular to the upper surface 101 or the lower surface 102 of the oxygen sensor, meaning that the diffusion barrier structure 20a is "longitudinally penetrating." This structural design eliminates the need for a test gas channel, preventing deformation of the test gas channel caused by pressure during lamination or static pressing. It also prevents the diffusion barrier structure 20a from rupturing due to shear forces or uneven compression from the test gas channel. Furthermore, the diffusion barrier structure 20a is supported by the first and second electrolyte layers 11a, 12a, preventing it from directly bearing the pressure of the lamination or static pressing processes, thereby maximizing the preservation of its overall shape. Therefore, the solution presented in the embodiments of this application avoids the challenges of forming and maintaining the shape of the gas channel to be measured during the manufacturing process, as well as the problems of uneven extrusion, cracking, and compression deformation of the diffusion barrier structure 20a. Furthermore, the technical solution presented in this application offers a simple structure, reducing manufacturing complexity. The overall shape and internal pore morphology of the diffusion barrier structure 20a can be easily controlled, thereby improving the manufacturing yield and detection accuracy of the oxygen sensor.

[0052] The shape of the diffusion barrier structure 20a can be any structure that at least partially penetrates the upper and lower surfaces of the first electrolyte layer 11a. For example, referring to Figures 3 and 4 , the diffusion barrier structure 20a can be a diffusion barrier column, i.e., the diffusion barrier structure 20a is generally columnar, with a cross-sectional shape and dimensions that are substantially the same. For example, the diffusion barrier column can extend in a direction parallel to the stacking direction of the first and second electrolyte layers 11a, 12a. In other embodiments, the diffusion barrier column can extend in a vertical direction, perpendicular to the surfaces of the first and second electrolyte layers 11a, 12a. Of course, in other embodiments, the diffusion barrier column can extend at an angle substantially greater than 0° with the stacking direction of the first and second electrolyte layers 11a, 12a, i.e., the diffusion barrier column can extend in a non-parallel direction to the stacking direction of the first and second electrolyte layers 11a, 12a. It should be understood that, in addition to the diffusion barrier columns shown above, the diffusion barrier structure 20a may also be in other shapes, such as a substantially truncated cone-shaped diffusion barrier structure 20a.

[0053] During the manufacturing process, referring to Figures 3 and 4 , a through-hole can be formed in the first electrolyte layer 11a. Then, at least a portion of the diffusion barrier structure 20a can be formed within the through-hole using processes such as, but not limited to, filling and screen printing, thereby simplifying the configuration of the diffusion barrier structure 20a. Of course, during the manufacturing process, a through-hole can also be formed in the first electrolyte layer 11a. After forming the detection cavity 30a in the second electrolyte layer 12a, the first and second electrolyte layers 11a, 12a can be stacked. After the first and second electrolyte layers 11a, 12a are stacked together, a screen printing process can be used to form the columnar diffusion barrier structure 20a.

[0054] Exemplarily, the diffusion barrier structure 20a can be made of any one of porous zirconia or porous alumina. Exemplarily, the porosity of the diffusion barrier structure 20a can be approximately 20% to approximately 50%. Exemplarily, the porosity of the diffusion barrier structure 20a can be controlled to adjust the pressure difference between the detection chamber 30a and the gas to be measured outside the detection chamber 30a, thereby controlling the magnitude of the pump current. Since the diffusion mode of the gas to be measured in the diffusion barrier structure 20a is physical diffusion, once the porosity of the diffusion barrier structure 20a is determined, the limiting rate of diffusion of the gas to be measured into the detection chamber 30a is determined. Referring to Figures 3 and 4, the pump cell of the oxygen sensor includes a test electrode 53a and a common electrode, wherein the common electrode can be a first common electrode 51a. When a voltage is applied across the pump cell (test electrode 53a and first common electrode 51a), a current is generated within the pump cell due to the flow of oxygen ions, pumping oxygen into or out of the detection cavity 30a. Because the gas diffusion rate within the diffusion barrier structure 20a has a limit, the oxygen ion flow rate within the pump cell does not increase indefinitely with increasing applied voltage, resulting in a limiting oxygen ion current, also known as the pump current. Therefore, the magnitude of the pump current can be adjusted by adjusting the porosity of the diffusion barrier structure 20a.

[0055] Illustratively, referring to Figures 3 and 4 , a test electrode 53a is provided on the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a, and a common electrode is provided in the detection chamber 30a. The pump cell of the oxygen sensor includes the test electrode 53a and the common electrode. Illustratively, an electrode protective layer 61a may be provided on the surface of the test electrode 53a to protect it. Illustratively, the electrode protective layer 61a covers the portion of the test electrode 53a that contacts the rear-end connector. The connector connects the oxygen sensor to its control circuitry (not shown). The material of the electrode protective layer 61a may be at least one of zirconium oxide or aluminum oxide. Illustratively, the electrode protective layer 61a may be porous zirconium oxide or porous aluminum oxide. Illustratively, the porosity of the electrode protective layer 61a may be approximately 15% to approximately 45%.

[0056] For example, referring to Figures 3 and 4 , the oxygen sensor also includes a reference chamber 40a, which is used to accommodate a reference gas. A reference electrode 54a is disposed within the reference chamber 40a. The Nernst cell of the oxygen sensor includes the reference electrode 54a and a common electrode. The pump cell and Nernst cell described above constitute the functional unit of the oxygen sensor. The Nernst cell is used to detect the oxygen partial pressure difference between the test gas entering the detection chamber 30a and the reference gas within the reference chamber 40a, and outputs feedback in the form of an electrical signal. The pump cell is used to adjust the oxygen partial pressure in the detection chamber 30a, maintaining the electrical signal output by the Nernst cell at approximately 450 mV.

[0057] Exemplarily, referring to Figures 3 and 4, the common electrode in the detection chamber 30a may include a first common electrode 51a and a second common electrode 52a, wherein the first common electrode 51a is located above the detection chamber 30a, and the second common electrode 52a is located below the detection chamber 30a. Exemplarily, the first common electrode 51a may be disposed on the lower surface of the first electrolyte layer 11a, and the second common electrode 52a may be disposed on the upper surface of another electrolyte layer and opposite to the first common electrode 51a. Exemplarily, the pump cell of the oxygen sensor may include the first common electrode 51a and the test electrode 53a. Exemplarily, the Nernst cell of the oxygen sensor may include a reference electrode 54a and a second common electrode 52a. Of course, in other embodiments, only the first common electrode 51a or the second common electrode 52a may be provided.

[0058] The reference chamber 40a can be arranged in a variety of ways, and several such arrangements are exemplarily described below.

[0059] For example, the reference chamber 40a can be located in a different electrolyte layer from the detection chamber 30a. For example, the reference chamber 40a can be located below the detection chamber 30a. For example, referring to Figures 3 and 4, the oxygen sensor can further include: a third electrolyte layer 13a and a fourth electrolyte layer 14a, wherein the third electrolyte layer 13a is laminated on the surface of the second electrolyte layer 12a facing away from the first electrolyte layer 11a; and the fourth electrolyte layer 14a is laminated on the surface of the third electrolyte layer 13a facing away from the second electrolyte layer 12a. The reference chamber 40a can be located within the fourth electrolyte layer 14a. For example, the reference chamber 40a can have a third chamber wall 41 and a fourth chamber wall 42 positioned opposite each other, wherein the third chamber wall 41 is located on the surface of the third electrolyte layer 13a facing the fourth electrolyte layer 14a. The reference electrode 54a can be disposed on the third chamber wall 41, that is, on the surface of the third electrolyte layer 13a facing the fourth electrolyte layer 14a.

[0060] Of course, in other embodiments, the reference chamber 40a can be provided in the second electrolyte layer 12a, and the reference chamber 40a is separated from the detection chamber 30a by the second electrolyte layer 12a. That is, the detection chamber 30a and the reference chamber 40a are located in the same electrolyte layer. Exemplarily, two cavities are provided in the second electrolyte layer 12a, and the two cavities are separated by the second electrolyte layer 12a. One of the cavities is used as the detection chamber 30a for entering the gas to be measured. The other cavity serves as the reference chamber 40a for accommodating the reference gas. Of course, in other embodiments, the reference chamber 40a can also be a notch at the edge of the second electrolyte layer 12a, that is, the opening of the reference chamber 40a is exactly the notch opening at the edge of the second electrolyte layer 12a, so as to facilitate the reference gas to enter the reference chamber 40a. Exemplarily, the reference electrode 54a is disposed on the upper cavity wall (third cavity wall 41 ) of the reference cavity 40a. Of course, the reference electrode 54a may also be disposed on the lower cavity wall (fourth cavity wall 42 ) of the reference cavity 40a.

[0061] Exemplarily, with reference to FIG3 and FIG4, the oxygen sensor may further include: a heating layer for heating, the heating layer being used to heat structures such as but not limited to the reference chamber 40a and the detection chamber 30a, so that they quickly reach the operating temperature. Exemplarily, with reference to FIG3 and FIG4, the heating layer may be stacked on the surface of the fourth electrolyte layer 14a away from the third electrolyte layer 13a. In some embodiments, the total thickness of the heating layer and the fourth electrolyte layer 14a may be equal to the total thickness of the first electrolyte layer 11a, the second electrolyte layer 12a and the third electrolyte layer 13a. That is, the total thickness from the third electrolyte layer 13a longitudinally extending to the upper surface 101 of the oxygen sensor is equal to the total thickness from the fourth electrolyte layer 14a longitudinally extending to the lower surface 102 of the oxygen sensor. The thickness refers to the distance between the two opposing surfaces of the electrolyte layer in a direction perpendicular to the upper surface 101 or the lower surface 102 of the oxygen sensor. This arrangement creates a more symmetrical oxygen sensor structure, allowing the upper and lower halves to expand and contract as synchronously as possible during heating and cooling, minimizing the risk of bending, cracking, or delamination during sintering. Furthermore, the heat generated by the heating layer is transferred upwards along a more optimal path, further improving the sensor's accuracy.

[0062] When setting the heating layer, a variety of methods can be used. For example, with reference to Figures 3 and 4, the heating layer may include: a heating electrode 55a, an insulating layer 62a, a fifth electrolyte layer 15a, and a sixth electrolyte layer 16a. For example, with reference to Figures 3 and 4, the fifth electrolyte layer 15a may be stacked on the surface of the fourth electrolyte layer 14a facing away from the third electrolyte layer 13a. For example, with reference to Figures 3 and 4, the sixth electrolyte layer 16a may be stacked on the surface of the fifth electrolyte layer 15a facing away from the fourth electrolyte layer 14a. The heating electrode 55a is disposed in the insulating layer 62a, that is, the heating electrode 55a is surrounded by the insulating layer 62a. A cavity is provided in the fifth electrolyte layer 15a and the sixth electrolyte layer 16a, and the insulating layer 62a is disposed in the cavity. The heating electrode 55a is separated from the fifth electrolyte layer 15a and the sixth electrolyte layer 16a by the insulating layer 62a. The material of the insulating layer 62a may be, for example, but not limited to, alumina ceramic. For example, the material of the insulating layer 62a can be dense alumina. For example, the porosity of the dense alumina used as the material for setting the insulating layer 62a can be approximately less than 5%. For example, the porosity of the alumina ceramic used as the insulating layer 62a can be approximately less than 1%.

[0063] Exemplarily, the material of any one of the test electrode 53a, the common electrode, the reference electrode 54a, and the heater electrode 55a can be a platinum electrode. For example, the material of any one of the test electrode 53a, the common electrode, the reference electrode 54a, and the heater electrode 55a can be a platinum cermet electrode. Exemplarily, the mass fraction of platinum in the platinum cermet electrode can be approximately 40% to approximately 60%.

[0064] Exemplarily, the material of any of the above-mentioned electrolyte layers can be zirconia ceramic, that is, the material of any of the first electrolyte layer 11a to the sixth electrolyte layer 16a can be zirconia ceramic. Exemplarily, the material of any of the above-mentioned electrolyte layers can be zirconia ceramic doped with yttrium oxide or scandium oxide, that is, the material of any of the first electrolyte layer 11a to the sixth electrolyte layer 16a can be zirconia ceramic. Exemplarily, the molar mass of yttrium oxide or scandium oxide in the zirconia ceramic is approximately 3% to approximately 10%. At this doping concentration, the zirconia can have good electrical properties, thereby improving the detection accuracy of the oxygen sensor. Exemplarily, any of the above-mentioned electrolyte layers can be a dense electrolyte layer formed by sintering. Therefore, if the electrolyte layer is not porous, gas diffusion cannot be prevented, and gas diffusion is maximized through predetermined diffusion channels, such as but not limited to the diffusion barrier structure 20a, thereby improving the detection accuracy of the oxygen sensor.

[0065] In the various embodiments described above, by aligning the first end surface 21 of the diffusion barrier structure 20a with or protruding from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a, the gas to be measured passes through the diffusion barrier structure 20a and enters the detection cavity 30a. Compared to related art, the present application eliminates the need for a gas channel to be measured, thus preventing the gas channel from being squeezed and deformed, and also preventing the diffusion barrier structure 20a from being squeezed and damaged by the deformed gas channel, thereby improving detection accuracy.

[0066] Compared to related technologies, the structural designs shown in some of the above-mentioned embodiments do not require a test gas channel, nor do they require conformal plugging during subsequent lamination or static pressing processes. This avoids deformation of the test gas channel caused by pressure during lamination or static pressing, and also prevents the diffusion barrier structure 20a from being ruptured by shear forces from the test gas channel or uneven compression. Furthermore, the diffusion barrier structure 20a is supported by the first electrolyte layer 11a and the second electrolyte layer 12a, preventing it from directly bearing the pressure during lamination or static pressing, thereby maximizing the overall shape of the diffusion barrier structure 20a. Therefore, the solutions shown in the embodiments of the present application avoid issues with forming and conforming the test gas channel during the manufacturing process, as well as issues with uneven compression, deformation, and cracking of the diffusion barrier structure 20a, as well as compression deformation. Furthermore, the technical solutions shown in the present application are simple in structure, reducing manufacturing difficulty. The overall shape and internal pore morphology of the diffusion barrier structure 20a are easily controlled, thereby improving the manufacturing yield and detection accuracy of the oxygen sensor. It can be seen that although the diffusion barrier structure 20a shown in the present application is of a "longitudinal through-type", it can prevent the diffusion barrier structure 20a from being deformed and cracked due to uneven extrusion.

[0067] In addition, the present invention also provides a method for preparing an oxygen sensor. Referring to FIG. 3 and FIG. 4 , the method includes:

[0068] A detection cavity 30a is formed in the second electrolyte layer 12a;

[0069] Laminating a first electrolyte layer 11 a and a second electrolyte layer 12 a ;

[0070] A diffusion barrier structure 20a is formed that at least partially penetrates the first electrolyte layer 11a; the diffusion barrier structure 20a is connected to the detection cavity 30a; wherein, the diffusion barrier structure 20a has a first end face 21 on the side away from the second electrolyte layer 12a, and the first end face 21 is flush with or protrudes from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a.

[0071] In the above-described scheme, by aligning the first end surface 21 of the diffusion barrier structure 20a with or protruding from the surface of the first electrolyte layer 11a facing away from the second electrolyte layer 12a, the gas to be measured passes through the diffusion barrier structure 20a and enters the detection cavity 30a. Compared to related art, the present application eliminates the need for a gas channel to be measured, thus preventing the gas channel from being squeezed and deformed. It also prevents the diffusion barrier structure 20a from being squeezed and damaged by the deformed gas channel, thereby improving detection accuracy. The following describes each of the above steps in detail with reference to the accompanying drawings.

[0072] It should be noted that the steps of forming the detection cavity 30a in the second electrolyte layer 12a and stacking the first and second electrolyte layers 11a, 12a are not performed in any particular order. The steps of forming the diffusion barrier structure 20a that at least partially penetrates the first electrolyte layer 11a and stacking the first and second electrolyte layers 11a, 12a are also not performed in any particular order.

[0073] Exemplarily, with reference to FIG3 and FIG4, the preparation method may further include: forming a through hole in the first electrolyte layer 11a, and after the first electrolyte layer 11a and the second electrolyte layer 12a are stacked, the through hole is connected to the detection cavity 30a. That is, by adjusting the position of the through hole formed in the first electrolyte layer 11a, it is ensured that after the first electrolyte layer 11a and the second electrolyte layer 12a are stacked together, the through hole is connected to the detection cavity 30a. At this time, when forming a diffusion barrier structure 20a that at least partially penetrates the first electrolyte layer 11a, it may include forming a diffusion barrier structure 20a that at least fills the through hole. Of course, in addition to filling the through hole, the diffusion barrier structure 20a may also extend into the detection cavity 30a. The specific extent of extension can be referred to the description of the aforementioned oxygen sensor part and will not be repeated here.

[0074] During the manufacturing process, a through hole can be formed in the first electrolyte layer 11a. Then, at least a portion of the diffusion barrier structure 20a can be formed within the through hole using a process such as, but not limited to, filling or screen printing, thereby simplifying the configuration of the diffusion barrier structure 20a. Of course, during the manufacturing process, a through hole can also be formed in the first electrolyte layer 11a. After forming the detection cavity 30a in the second electrolyte layer 12a, the first and second electrolyte layers 11a, 12a can be stacked. After the first and second electrolyte layers 11a, 12a are stacked together, a screen printing process can be used to form the columnar diffusion barrier structure 20a.

[0075] There are many ways to form the through hole in the first electrolyte layer 11a. For example, laser drilling, mechanical drilling, etc. can be used to form the through hole in the first electrolyte layer 11a.

[0076] The detection cavity 30a can be formed in the second electrolyte layer 12a in a variety of ways. For example, the detection cavity 30a can be formed in the second electrolyte layer 12a by laser drilling, mechanical drilling, or the like.

[0077] For example, after stacking the first electrolyte layer 11a and the second electrolyte layer 12a in sequence and preparing the diffusion barrier structure, and then forming structures such as but not limited to the reference cavity 40a and the heating layer, the stacked structure can be sintered together to form an oxygen sensor.

[0078] In the related art, a thin covering layer is provided on the upper surface of the diffusion barrier structure. The covering layer is thin and only covers the upper surface of the diffusion barrier, that is, a covering layer of the same size as the diffusion barrier is provided on the upper surface of the diffusion barrier to seal and cover the diffusion barrier. However, this covering method results in a smaller coverage area of ​​the diffusion barrier. In the subsequent lamination molding process of the oxygen sensor, the smaller area of ​​the covering layer will cause the diffusion barrier to have a greater risk of rupture, increasing the difficulty of manufacturing; and the manufactured product is very likely to cause the diffusion barrier to be loosely sealed or incompletely covered, which brings difficulties to the precise control of the pump current and leads to a low product yield. In order to solve the above technical problems, the present application provides the following implementation methods.

[0079] The following describes some embodiments of the present application in detail with reference to the accompanying drawings. In the absence of conflict, the following embodiments and features therein may be combined with each other.

[0080] First, let's introduce the application scenario of the oxygen sensor illustrated in the example of this application. The oxygen sensor is used to measure the oxygen concentration in the gas to be measured. The oxygen sensor can be a wide-band oxygen sensor.

[0081] 5 to 7 , an embodiment of the present application provides another oxygen sensor, comprising: a first electrolyte layer 11 b, an electrolyte covering layer 17, and a second electrolyte layer 12 b stacked in sequence; wherein a first diffusion channel 71 is provided in the first electrolyte layer 11 b; at least one second diffusion channel 72 is provided in the electrolyte covering layer 17; and the total cross-sectional area of ​​all second diffusion channels 72 is substantially smaller than the cross-sectional area of ​​the first diffusion channel 71; and a diffusion barrier structure 20 b and a detection cavity 30 b are provided in the second electrolyte layer 12 b, wherein the diffusion barrier structure 20 b is in communication with the first diffusion channel 71 at least through the second diffusion channel 72, and the detection cavity 30 b is in communication with the second diffusion channel 72 at least through the diffusion barrier structure 20 b.

[0082] In the above-described embodiment, by adding an electrolyte cover layer 17 between the first electrolyte layer 11b and the second electrolyte layer 12b, the pressure exerted by the electrolyte cover layer 17 on the diffusion barrier structure 20b is more evenly distributed during the lamination process of the oxygen sensor, preventing the diffusion barrier structure 20b from cracking and improving product yield. The following describes each of the above-described structures in detail with reference to the accompanying drawings.

[0083] When setting the first electrolyte layer 11b, referring to Figures 5 to 7, the material of the first electrolyte layer 11b can be a solid electrolyte layer. A first diffusion channel 71 is provided in the first electrolyte layer 11b, that is, the first diffusion channel 71 runs through the upper and lower opposite surfaces of the first electrolyte layer 11b. The first diffusion channel 71 is used to enter the gas to be measured, that is, the first diffusion channel 71 is connected to the gas to be measured, so that the gas to be measured can enter the first diffusion channel 71. Exemplarily, the first diffusion channel 71 may only include diffusion holes as shown in Figures 5 to 7. Of course, in some embodiments, the first diffusion channel 71 may also include a porous filler filled in the diffusion hole. That is, as long as the diffusion channel is set in a way that can diffuse the gas to be measured, it is within the protection scope of the first diffusion channel 71 in the embodiment of the present application.

[0084] When providing the second electrolyte layer 12b, referring to Figures 5 to 7 , the material of the second electrolyte layer 12b can be a solid electrolyte layer. A diffusion barrier structure 20b and a detection cavity 30b are provided in the second electrolyte layer 12b. The diffusion barrier structure 20b is connected to the first diffusion channel 71 at least through the second diffusion channel 72, and the detection cavity 30b is connected to the second diffusion channel 72 at least through the diffusion barrier structure 20b. This allows the gas to enter the detection cavity 30b through at least the first diffusion channel 71, the second diffusion channel 72, and the diffusion barrier structure 20b.

[0085] The diffusion barrier structure 20b and detection cavity 30b can be provided in the second electrolyte layer 12b in a variety of ways. For example, referring to Figures 5 to 7 , the second electrolyte layer 12b can include a receiving through-hole, i.e., the receiving through-hole extends through two opposing upper and lower surfaces of the second electrolyte layer 12b. The diffusion barrier structure 20b and detection cavity 30b are provided within the receiving through-hole, i.e., the diffusion barrier structure 20b and detection cavity 30b are disposed within the receiving through-hole. The diffusion barrier structure 20b separates the detection cavity 30b from the first diffusion channel 71, meaning that the gas to be measured entering the first diffusion channel 71 must at least pass through the diffusion barrier structure 20b before entering the detection cavity 30b. The diffusion barrier structure 20b can be a layered structure with a certain porosity, allowing the gas to pass through the diffusion barrier structure 20b and enter the detection cavity 30b. For example, the diffusion barrier structure 20b can be porous zirconia or porous alumina, and the porosity of the diffusion barrier structure 20b can be approximately 20% to approximately 50%. For example, the porosity of the diffusion barrier structure 20b can be controlled to adjust the diffusion rate of the gas to be measured through the diffusion barrier structure 20b and into the detection cavity 30b, thereby controlling the magnitude of the pump current. Since the gas to be measured in the diffusion barrier structure 20b diffuses physically, once the porosity of the diffusion barrier structure 20b is determined, the limiting rate at which the gas to be measured diffuses into the detection cavity 30b is determined. Referring to Figures 5 to 7 , the pump cell of the oxygen sensor includes a test electrode 53b and a common electrode, which can be a first common electrode 51b. When a voltage is applied across the pump cell (the test electrode 53b and the first common electrode 51b), a current is generated within the pump cell due to the flow of oxygen ions, pumping oxygen into or out of the detection cavity 30b. Since the gas diffusion rate within the diffusion barrier structure 20b has a limit, the oxygen ion flow rate within the pump cell does not increase indefinitely with increasing applied voltage, resulting in a limiting oxygen ion current, also known as the pump current. Therefore, the magnitude of the pump current can be adjusted by adjusting the porosity of the diffusion barrier structure 20b. For example, the upper end of the receiving through hole contacts the electrolyte cover layer 17 , and the lower end of the receiving through hole may contact other electrolyte layers.

[0086] When providing the electrolyte cover layer 17, referring to Figures 5 and 6, the electrolyte cover layer 17 is sandwiched between the first electrolyte layer 11b and the second electrolyte layer 12b. The first electrolyte layer 11b, electrolyte cover layer 17, and second electrolyte layer 12b are stacked sequentially. The electrolyte cover layer 17 is used to seal and cover the diffusion barrier 20b, improving the sealing density of the diffusion barrier 20b. At least one second diffusion channel 72 is provided in the electrolyte cover layer 17. Each second diffusion channel 72 extends through two opposing upper and lower surfaces of the electrolyte cover layer 17. The total cross-sectional area of ​​all second diffusion channels 72 is substantially smaller than the cross-sectional area of ​​the first diffusion channel 71. Regardless of whether there is one, two, or more second diffusion channels 72, the total cross-sectional area of ​​all second diffusion channels 72 must still be substantially smaller than the cross-sectional area of ​​the first diffusion channel 71. This ensures that the addition of the electrolyte cover layer 17 provides better coverage and sealing of the diffusion barrier 20b than when the first electrolyte layer 11b is directly stacked on the second electrolyte layer 12b. Furthermore, the first diffusion channel 71 is able to communicate with the second diffusion channel 72. That is, the gas to be measured entering from the first diffusion channel 71 can pass through the second diffusion channel 72, through the electrolyte cover layer 17, and at least through the diffusion barrier structure 20b into the detection chamber 30b. In other words, the diffusion barrier structure 20b is in communication with the first diffusion channel 71 at least through the second diffusion channel 72, and the detection chamber 30b is in communication with the second diffusion channel 72 at least through the diffusion barrier structure 20b, so that the gas to be measured enters the detection chamber 30b through at least the first diffusion channel 71, the second diffusion channel 72, and the diffusion barrier structure 20b.

[0087] Compared to related art, the present embodiment adds an electrolyte cover layer 17 between the first electrolyte layer 11b and the second electrolyte layer 12b. The edges of the holes of the first diffusion channel 71 press against the electrolyte cover layer 17, and the area of ​​the electrolyte cover layer 17 is significantly larger than that of the diffusion barrier 20b. During the lamination process of the oxygen sensor, the electrolyte cover layer 17 evenly distributes the concentrated stress at the edges of the holes of the first diffusion channel 71 to the diffusion barrier 20b and the second electrolyte layer 12b, resulting in a more uniform pressure distribution on the diffusion barrier 20b, preventing the diffusion barrier 20b from cracking and improving product yield. It can be seen that the present embodiment replaces the smaller cover layer covering the upper surface of the diffusion barrier 20b in related art, solving the problem of a poorly sealed or incomplete cover layer on the upper portion of the diffusion barrier 20b, which can cause cracks or leaks in the cover layer or the diffusion barrier 20b during subsequent molding, thus complicating pump current control. Furthermore, the oxygen sensor shown in the present embodiment has a simpler structure, is easier to manufacture, and offers a better sealing effect, improving the accuracy of pump current control. The manufacturing difficulty of the oxygen sensor is reduced, and the manufacturing yield and control accuracy of the oxygen sensor are improved.

[0088] Each second diffusion channel 72 may be positioned opposite the first diffusion channel 71, so that each second diffusion channel 72 can communicate with the first diffusion channel 71 to diffuse the gas to be measured in the first diffusion channel 71 into the second diffusion channel 72. For example, the cross-sectional dimensions of each second diffusion channel 72 may be substantially smaller than the cross-sectional dimensions of the first diffusion channel 71, and each second diffusion channel 72 is positioned opposite the first diffusion channel 71, so that the total cross-sectional area of ​​all second diffusion channels 72 is substantially smaller than the cross-sectional area of ​​the first diffusion channel 71.

[0089] The electrolyte covering layer 17 may be a thin solid electrolyte layer, and the length and width of the electrolyte covering layer 17 may be substantially equal to the length and width of other electrolyte layers.

[0090] Regarding the number of the second diffusion channels 72, it can be one or more. Exemplarily, when the number of the second diffusion channels 72 is multiple, the multiple second diffusion channels 72 can be arranged in a manner such as but not limited to array arrangement, single row arrangement, random distribution, etc. Exemplarily, referring to Figures 5 to 7, the second diffusion channels 72 may include diffusion through-holes, that is, the second diffusion channels 72 are diffusion through-hole structures opened on the electrolyte covering layer 17. Of course, in other embodiments, the second diffusion channels 72 may also include porous fillers filled in the diffusion through-holes, that is, the second diffusion channels 72 are diffusion channels formed by porous fillers filled in the diffusion through-holes. It should be understood that any diffusion channel method that can diffuse the gas to be measured is within the protection scope of the embodiment of the present application regarding the setting method of the second diffusion channel 72. In addition, it should be noted that the total number of second diffusion channels 72, the cross-sectional area of ​​each second diffusion channel 72, and the total cross-sectional area of ​​all second diffusion channels 72 are related to the target pump current of the control, that is, these parameters are specifically related to the pressure difference in the diffusion steady state of the gas to be measured between the outside of the detection chamber 30b and the inside of the detection chamber 30b.

[0091] The second diffusion channel 72 may be a diffusion slit with a rectangular cross-section. The diffusion slit has a length of approximately 100 μm to approximately 300 μm and a width of approximately 5 μm to approximately 500 μm. For example, the diffusion slit length may be any value between approximately 100 μm and approximately 300 μm, such as 100 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 220 μm, 240 μm, 260 μm, 280 μm, or 300 μm. For example, the diffusion slit width may be any value between approximately 5 μm and approximately 50 μm, such as 5 μm, 10 μm, 20 μm, 40 μm, or 50 μm. For example, the number of diffusion slits may be any one of 1, 2, 3, 4, 5, or 6. The diffusion slits can be formed using methods such as, but not limited to, laser drilling or mechanical drilling to connect the first diffusion channel 71 and the third diffusion channel 73, allowing the gas to enter the diffusion barrier structure 20b and ultimately the detection cavity 30b. The size and number of the diffusion slits in the electrolyte cover layer 17 can be adjusted according to the pump current control requirements. It should be understood that the shape of the second diffusion channel 72 is not limited to a diffusion slit with a roughly rectangular cross-section; other configurations are also possible. For example, a generally microporous structure can also be used as the second diffusion channel 72.

[0092] Exemplarily, the thickness of the electrolyte cover layer 17 is about 50 μm to about 200 μm. For example, the thickness of the electrolyte cover layer 17 can be any value between about 50 μm and about 200 μm, such as 50 μm, 75 μm, 100 μm, 125 μm, 150 μm, 175 μm, 200 μm, etc. Compared to the thickness of the cover layer in the related art, which is generally no more than 30 microns, the thickness of the electrolyte cover layer 17 in the present application is about 50 μm to about 200 μm, which is relatively thick, thus more resistant to pressure, and can also more evenly distribute the pressure during the preparation process, and the product yield can be controlled.

[0093] When determining the material for the electrolyte cover layer 17, a variety of materials can be used. Exemplarily, the material for the electrolyte cover layer 17 can be a zirconia ceramic doped with yttrium oxide or scandium oxide; wherein the molar mass of yttrium oxide or scandium oxide in the zirconia ceramic is approximately 3% to approximately 8%. Exemplarily, the material for the electrolyte cover layer 17 can be a zirconia ceramic doped with yttrium oxide; the molar mass of yttrium oxide in the zirconia ceramic can be any value between approximately 3% and approximately 8%, such as 3%, 4%, 5%, 6%, 7%, or 8%. Exemplarily, the electrolyte cover layer 17 can be a dense electrolyte layer formed by sintering. Therefore, if the electrolyte cover layer 17 is not porous, gas diffusion cannot occur, allowing gas to diffuse as much as possible through the pre-set second diffusion channel 72, thereby improving the detection accuracy of the oxygen sensor.

[0094] There are many ways to arrange the diffusion barrier structure 20b and the detection cavity 30b in the receiving through hole. Several arrangement methods are exemplified below.

[0095] For example, referring to FIG5 , a third diffusion channel 73 is provided within the diffusion barrier structure 20b. The third diffusion channel 73 communicates with the first diffusion channel 71 via the second diffusion channel 72. The third diffusion channel 73 also communicates with the detection chamber 30b via the diffusion barrier structure 20b. This allows the gas to enter the detection chamber 30b through the third diffusion channel 73 and the diffusion barrier structure 20b. Specifically, the third diffusion channel 73 is further provided within the receiving through-hole. The gas to be measured entering the second diffusion channel 72 first enters the third diffusion channel 73, then enters the diffusion barrier structure 20b, and then enters the detection chamber 30b. In this embodiment, the first diffusion channel 71 forms the upper end of the gas to be measured channel, while the third diffusion channel 73 forms the lower end of the gas to be measured channel. The upper and lower ends of the gas to be measured channel are connected by the second diffusion channel 72 in the electrolyte cover layer 17. This establishes a diffusion path for the gas to be measured to diffuse into the diffusion barrier structure 20b, facilitating current control of the pump cell. When providing the third diffusion channel 73, referring to FIG5 , the third diffusion channel 73 may be a diffusion through-hole. Of course, in other embodiments, the third diffusion channel 73 may also include a porous filler filled within the diffusion through-hole, i.e., the third diffusion channel 73 is formed using a porous filler filled within the diffusion through-hole. It should be understood that any diffusion channel capable of diffusing the gas to be measured is within the scope of protection of the configuration of the third diffusion channel 73 in the embodiments of this application.

[0096] Exemplarily, with reference to FIG5 , the cross-sectional shape of the diffusion barrier structure 20b may be annular, that is, the diffusion barrier structure 20b is an annular layer structure. Exemplarily, the annular shape may be a closed annular shape such as, but not limited to, a circular annular shape. Among them, the third diffusion channel 73 may be a diffusion through-hole at the center of the diffusion barrier structure 20b, and the detection cavity 30b is located outside the diffusion barrier structure 20b. That is, by adopting an annular diffusion barrier structure 20b, the diffusion through-hole at the center of the diffusion barrier structure 20b is utilized as the third diffusion channel 73, which is positioned opposite to and connected to the second diffusion channel 72. The detection cavity 30b is located outside the diffusion barrier structure 20b, separated from the third diffusion channel 73, so that the gas entering the third diffusion channel 73 needs to pass through the diffusion barrier structure 20b to enter the detection cavity 30b.

[0097] Illustratively, referring to FIG5 , the cross-sectional area of ​​the third diffusion channel 73 is substantially larger than the total cross-sectional area of ​​all second diffusion channels 72. This facilitates the formation of larger third diffusion channels 73 within the diffusion barrier structure 20b, facilitating current regulation of the pump cell. Illustratively, each second diffusion channel 72 is positioned opposite a third diffusion channel 73, facilitating smooth diffusion of the gas to be measured within the second diffusion channels 72 into the third diffusion channels 73. Illustratively, the cross-sectional dimensions of the third diffusion channel 73 are substantially larger than the cross-sectional dimensions of each second diffusion channel 72, and each second diffusion channel 72 is positioned opposite a third diffusion channel 73. This facilitates the formation of larger third diffusion channels 73 within the diffusion barrier structure 20b, facilitating current regulation of the pump cell.

[0098] For example, referring to FIG5 , the third diffusion channel 73 can have a cross-sectional size equal to that of the first diffusion channel 71 and have an opposite cross-sectional position. That is, the cross-sectional shape of the third diffusion channel 73 is exactly the same as that of the first diffusion channel 71, and the positions are completely opposite, thereby reducing the pressure concentration effect on the electrolyte cover layer 17 and the diffusion barrier structure 20b at the pore edges of the first diffusion channel 71.

[0099] It should be understood that the second diffusion channel 72 is not limited to being connected to the diffusion barrier structure 20b through the third diffusion channel 73, and other methods may also be used.

[0100] For example, referring to Figures 6 and 7 , each second diffusion channel 72 can be positioned opposite the diffusion barrier structure 20b, with the space in the accommodating through-hole excluding the diffusion barrier structure 20b forming a detection cavity 30b, so that the gas to be measured entering through the second diffusion channel 72 passes through the diffusion barrier structure 20b and enters the detection cavity 30b. In this manner, the diffusion barrier structure 20b is directly positioned opposite the second diffusion channel 72, so that the gas to be measured entering through the second diffusion channel 72 directly enters the diffusion barrier structure 20b and then enters the detection cavity 30b through the diffusion barrier structure 20b. In this case, the arrangement of the diffusion barrier structure 20b and the detection cavity 30b can also be adopted in a variety of ways.

[0101] For example, referring to Figure 6 , the accommodating through-hole can be a large, circular cross-section. The diffusion barrier structure 20b can be disc-shaped, with a cross-sectional area substantially smaller than that of the accommodating through-hole. The diffusion barrier structure 20b is positioned opposite the second diffusion channel 72, eliminating the need for a third diffusion channel 73 within the diffusion barrier structure 20b. The detection chamber 30b is an annular chamber, meaning that the diffusion barrier structure 20b is located directly in the center of the accommodating through-hole.

[0102] For example, referring to Figure 7 , the accommodating through-hole can be a large through-hole with a rectangular cross-section. The diffusion barrier structure 20b can be roughly rectangular in shape, with a cross-sectional area substantially smaller than that of the accommodating through-hole. The diffusion barrier structure 20b is positioned opposite the second diffusion channel 72, eliminating the need for the third diffusion channel 73 within the diffusion barrier structure 20b. Furthermore, the diffusion barrier structure 20b is located to the left of the accommodating through-hole, while the detection chamber 30b is located to the right of the accommodating through-hole.

[0103] Exemplarily, referring to Figures 5 to 7 , a test electrode 53b is disposed on the surface of the first electrolyte layer 11b facing away from the electrolyte cover layer 17, and a common electrode is disposed in the detection cavity 30b. The pump cell of the oxygen sensor includes the test electrode 53b and the common electrode, forming an oxygen pump unit including the test electrode 53b and the common electrode. Exemplarily, an electrode protective layer 61b may be coated on the surface of the test electrode 53b to protect the test electrode 53b. Exemplarily, the electrode protective layer 61b may be porous zirconia or porous alumina, and the porosity of the electrode protective layer 61b may be approximately 15% to approximately 45%.

[0104] 5 to 7 , the oxygen sensor further includes a reference chamber 40 b for accommodating a reference gas. A reference electrode 54 b is disposed in the reference chamber 40 b . The Nernst cell of the oxygen sensor includes the reference electrode 54 b and a common electrode.

[0105] Exemplarily, referring to Figures 5 to 7, the common electrode in the detection chamber 30b may include a first common electrode 51b and a second common electrode 52b, wherein the first common electrode 51b is located above the detection chamber 30b and the second common electrode 52b is located below the detection chamber 30b. Exemplarily, the first common electrode 51b may be disposed on the lower surface of the electrolyte covering layer 17, and the second common electrode 52b may be disposed on the upper surface of another electrolyte layer and opposite to the first common electrode 51b. Exemplarily, the pump cell of the oxygen sensor may include a first common electrode 51b and a test electrode 53b. Exemplarily, the Nernst cell of the oxygen sensor may include a reference electrode 54b and a second common electrode 52b. Of course, in other embodiments, only the first common electrode 51b or the second common electrode 52b may be provided.

[0106] The reference chamber 40b can be arranged in a variety of ways, and several such arrangements are exemplarily described below.

[0107] Exemplarily, referring to Figure 7, the reference chamber 40b can be arranged in the second electrolyte layer 12b, and the reference chamber 40b is separated from the detection chamber 30b by the second electrolyte layer 12b. Exemplarily, the reference chamber 40b can be separated from the accommodating through-hole by the second electrolyte layer 12b, so as to ensure that the reference chamber 40b and the detection chamber 30b are separated by the second electrolyte layer 12b. That is, the detection chamber 30b and the reference chamber 40b are located in the same electrolyte layer. Exemplarily, two cavities are provided in the second electrolyte layer 12b, and the two cavities are separated by the second electrolyte layer 12b. One of the cavities is used as an accommodating through-hole to set the diffusion barrier structure 20b and the detection chamber 30b. The other cavity is used as a reference chamber 40b for accommodating a reference gas. Of course, in other embodiments, the reference chamber 40b can also be a gap at the edge of the second electrolyte layer 12b, that is, the opening of the reference chamber 40b is exactly the gap opening at the edge of the second electrolyte layer 12b, thereby facilitating the reference gas to enter the reference chamber 40b.

[0108] Exemplarily, the reference electrode 54b is disposed on the upper cavity wall of the reference cavity 40b. Of course, the reference electrode 54b may also be disposed on the lower cavity wall of the reference cavity 40b.

[0109] For example, the reference chamber 40b can also be arranged at a position in a different electrolyte layer from the detection chamber 30b. For example, the reference chamber 40b can also be arranged below the detection chamber 30b. For example, with reference to Figures 5 and 6, the third electrolyte layer 13b can be stacked on the surface of the second electrolyte layer 12b facing away from the electrolyte cover layer 17, and the fourth electrolyte layer 14b can be stacked on the surface of the third electrolyte layer 13b facing away from the second electrolyte layer 12b, and the reference chamber 40b can be arranged in the fourth electrolyte layer 14b. For example, the reference electrode 54b can be arranged on the lower surface of the third electrolyte layer 13b.

[0110] 5 to 7 , the oxygen sensor may further include a heating unit for heating structures such as, but not limited to, the reference chamber 40 b and the detection chamber 30 b. The heating unit may be provided in a variety of ways.

[0111] For example, with reference to Figures 5 to 7, the heating unit may include: a heating electrode 55b, an insulating layer 62b, and a fifth electrolyte layer 15b. A cavity is provided in the fifth electrolyte layer 15b, the heating electrode 55b is provided in the cavity, and the heating electrode 55b is separated from the fifth electrolyte layer 15b by the insulating layer 62b, that is, the heating electrode 55b is surrounded by the insulating layer 62b. The material of the insulating layer 62b may be, for example, but not limited to, alumina ceramic. For example, the porosity of the alumina ceramic serving as the insulating layer 62b may be approximately less than 1%. For example, with reference to Figure 5, the fifth electrolyte layer 15b may be stacked on the surface of the fourth electrolyte layer 14b facing away from the third electrolyte layer 13b. For example, with reference to Figure 6, the fifth electrolyte layer 15b may be stacked on the surface of the third electrolyte layer 13b facing away from the second electrolyte layer 12b.

[0112] For example, the material of any one of the test electrode 53b, the common electrode, the reference electrode 54b and the heating electrode 55b can be a platinum metal ceramic electrode. For example, the mass fraction of platinum in the platinum metal ceramic electrode can be about 40% to about 60%.

[0113] Exemplarily, the material of any of the above-mentioned electrolyte layers can be a zirconia ceramic doped with yttria or scandia. Exemplarily, the molar mass of yttria or scandia in the zirconia ceramic is approximately 3% to approximately 8%. Exemplarily, any of the above-mentioned electrolyte layers can be a dense electrolyte layer formed by sintering. Thus, if the electrolyte layer is not porous, gas diffusion is prevented, and gas diffusion is maximized through pre-defined diffusion channels, such as, but not limited to, the diffusion barrier structure 20b, thereby improving the detection accuracy of the oxygen sensor.

[0114] In the various embodiments shown above, by adding an electrolyte covering layer 17 between the first electrolyte layer 11b and the second electrolyte layer 12b, the pressure distribution of the electrolyte covering layer 17 on the diffusion barrier structure 20b is relatively uniform during the lamination molding process of the oxygen sensor, preventing the diffusion barrier structure 20b from rupturing and improving the product yield. This avoids the covering layer above the diffusion barrier structure 20b having a small coverage area and size, which may cause the covering layer or the diffusion barrier structure 20b to rupture or deform during the subsequent molding process of the oxygen sensor, resulting in poor sealing or incomplete coverage of the diffusion barrier structure 20b, which may cause difficulties in regulating the pump current of the oxygen sensor. In addition, the oxygen sensor shown in the embodiment of the present application has a simpler structure, is easier to manufacture, has a better sealing effect, and improves the accuracy of pump current regulation. This reduces the manufacturing difficulty of the oxygen sensor and also improves the manufacturing yield and control accuracy of the oxygen sensor.

[0115] In addition, the present invention also provides a method for preparing an oxygen sensor. Referring to FIG. 5 to FIG. 7 , the method includes:

[0116] A first diffusion channel 71 is formed in the first electrolyte layer 11b;

[0117] forming a diffusion barrier structure 20b and a detection cavity 30b in the second electrolyte layer 12b;

[0118] At least one second diffusion channel 72 is formed in the electrolyte cover layer 17; and the total cross-sectional area of ​​all the second diffusion channels 72 is substantially smaller than the cross-sectional area of ​​the first diffusion channel 71;

[0119] The first electrolyte layer 11b, the electrolyte covering layer 17 and the second electrolyte layer 12b are stacked in sequence; the diffusion barrier structure 20b is connected to the first diffusion channel 71 at least through the second diffusion channel 72, and the detection cavity 30b is connected to the second diffusion channel 72 at least through the diffusion barrier structure 20b.

[0120] In the above scheme, by adding an electrolyte cover layer 17 between the first electrolyte layer 11b and the second electrolyte layer 12b, the pressure of the electrolyte cover layer 17 on the diffusion barrier structure 20b is more evenly distributed during the lamination process of the oxygen sensor, preventing the diffusion barrier structure 20b from cracking and improving product yield. The following describes each of the above steps in detail with reference to the accompanying figures.

[0121] It should be noted that the steps of forming the first diffusion channel 71 in the first electrolyte layer 11b and forming the diffusion barrier structure 20b and the detection cavity 30b in the second electrolyte layer 12b are not performed in any particular order and can be performed simultaneously or in separate steps. The steps of providing the second diffusion channel 72 in the electrolyte cover layer 17 and stacking the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b in sequence are not performed in any particular order. For example, the second diffusion channel 72 can be provided in the electrolyte cover layer 17 first, followed by stacking the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b in sequence. Alternatively, the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b can be stacked in sequence first, followed by providing the second diffusion channel 72 in the electrolyte cover layer 17.

[0122] There are various methods that can be used to form the first diffusion channel 71 in the first electrolyte layer 11b. For example, the first diffusion channel 71 can be formed in the first electrolyte layer 11b by laser drilling, mechanical drilling, or the like.

[0123] There are many ways to set the diffusion barrier structure 20b and the detection cavity 30b in the second electrolyte layer 12b. For example, the second electrolyte layer 12b can be provided with a accommodating through-hole, that is, the accommodating through-hole passes through the upper and lower opposite surfaces of the second electrolyte layer 12b. The diffusion barrier structure 20b and the detection cavity 30b are provided in the accommodating through-hole, that is, the diffusion barrier structure 20b and the detection cavity 30b are arranged in the accommodating through-hole. Among them, when forming the accommodating through-hole in the second electrolyte layer 12b, there are many ways to adopt. For example, the accommodating through-hole can be formed in the second electrolyte layer 12b by laser drilling, mechanical drilling, etc. There are many ways to form the diffusion barrier structure 20b in the accommodating through-hole. For example, the diffusion barrier structure 20b shown in the above-mentioned oxygen sensor part can be formed in the accommodating through-hole by processes such as, but not limited to, screen printing and filling. In the process of forming the diffusion barrier structure 20b, the detection cavity 30b can be formed at the same time.

[0124] There are many ways to provide at least one second diffusion channel 72 in the electrolyte cover layer 17. For example, the second diffusion channel 72 can be formed in the electrolyte cover layer 17 by laser drilling, mechanical drilling, etc.

[0125] The positions of the first diffusion channel 71, the second diffusion channel 72, and the accommodating through-hole can be adjusted. After the first electrolyte layer 11b, the electrolyte covering layer 17, and the second electrolyte layer 12b are stacked in sequence by stacking molding, it is ensured that each second diffusion channel 72 is positioned opposite to the first diffusion channel 71, the diffusion barrier structure 20b is connected to the first diffusion channel 71 at least through the second diffusion channel 72, and the detection cavity 30b is connected to the second diffusion channel 72 at least through the diffusion barrier structure 20b, so that the gas to be measured enters the detection cavity 30b through at least the first diffusion channel 71, the second diffusion channel 72, and the diffusion barrier structure 20b.

[0126] For example, after stacking the first electrolyte layer 11b, the electrolyte covering layer 17 and the second electrolyte layer 12b in sequence, and then forming structures such as but not limited to the reference chamber 40b and the heating unit, the stacked structure can be sintered together to form an oxygen sensor.

[0127] Exemplarily, before forming at least one second diffusion channel 72 in the electrolyte cover layer 17, the preparation method may further include: sintering the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b stacked in sequence. That is, after sintering the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b stacked in sequence, at least one second diffusion channel 72 is formed in the electrolyte cover layer 17. Exemplarily, after forming the first diffusion channel 71 in the first electrolyte layer 11b and forming the diffusion barrier structure 20b and the detection cavity 30b in the second electrolyte layer 12b, the first electrolyte layer 11b, the electrolyte cover layer 17, and the second electrolyte layer 12b stacked in sequence are sintered.

[0128] The present application provides a sensor element, as shown in FIG8 . Sensor element 200a includes the aforementioned oxygen sensor 100a or oxygen sensor 100b, and a protective layer 210a, which is applied to oxygen sensor 100a (100b). Protective layer 210a comprises approximately 85% to 95% by weight of a ceramic phase and approximately 5% to 15% by weight of a binder phase. The ceramic phase comprises one or both of Al2O3 and ZrO2. The binder phase is a three-phase melt, with a first phase comprising MgO, a second phase comprising SiO2, and a third phase comprising one of CaO, TiO2, or Al2O3. In other words, the ceramic phase can be Al2O3, ZrO2, or both Al2O3 and ZrO2. The binder phase is primarily derived from sintering aid raw materials used in the protective layer preparation process. In one embodiment of the present application, the melting point of the binder phase is approximately 1000°C to approximately 1300°C. The sintering aid is a mixture of three substances, which can be MgO, SiO2, and CaCO3, MgO, SiO2, and TiO2, or MgO, SiO2, and Al2O3. The combination of these sintering aids can form a molten state of three phases, MgO-SiO2-CaO, MgO-SiO2-TiO2, or MgO-SiO2-Al2O3, at relatively low temperatures. This allows the mixture to flow, allowing the solid particles in the raw materials to bond together, thereby enhancing the bonding strength within the protective layer and improving the bonding between the protective layer 210a and the oxygen sensor 100a (100b).

[0129] In some embodiments, the mass ratio of the first phase, the second phase, and the third phase is approximately (0.4-1.5):1:(0.3-1.5). The mass ratio of the three phases within this range makes the protective layer 210a more stable and less likely to fall off.

[0130] As shown in FIG9 , a solid electrolyte, electrodes, and a gas channel are disposed inside the detection portion of the sensor element 200 a . The protective layer 210 a can protect the components disposed inside the sensor element 200 a .

[0131] The pores in protective layer 210a serve to provide a path for exhaust gases. Through these pores, the sensor element can detect the oxygen concentration in the engine exhaust and transmit a signal to the engine control unit, thereby controlling the engine's combustion efficiency and emissions. Therefore, the porosity of protective layer 210a is crucial to the sensor element. In some embodiments, the porosity of protective layer 210a is approximately 20% to approximately 40%, and the pore size is approximately 0.2 μm to approximately 5 μm. Porosity and pore size within this range facilitate optimal exhaust gas flow from sensor element 200a.

[0132] The thickness of the protective layer 210a has a certain impact on the performance of the sensor element 200a. The main function of the protective layer 210a is to protect the electrodes and internal electrolyte of the sensor element 200a from damage by high temperatures and harmful substances in the exhaust gas. In some embodiments, the thickness of the protective layer 210a is about 300μm to about 800μm. The thickness of the protective layer 210a within this range has good heat resistance and corrosion resistance, thereby extending the life of the sensor element 200a; if the thickness is too thick, it may slow down the response speed of the sensor element 200a because the gas needs to travel a longer path to reach the electrode of the sensor element 200a. If the protective layer is too thin, it affects the heat resistance and corrosion resistance. The thickness of the protective layer 210a is also related to the method used to coat the slurry. The thickness of the protective layer 210a can be 400μm or 600μm.

[0133] The bonding strength between the protective layer 210a and the oxygen sensor 100a (100b) is crucial to the performance of the sensor element 200a. The higher the bonding strength, the stronger the adhesion between the protective layer 210a and the oxygen sensor 100a (100b), thereby better preventing harmful substances in the exhaust gas from penetrating into the interior of the sensor element 200a and protecting the electrodes and electrolyte from damage. In one embodiment of the present application, the bonding strength between the protective layer 210a and the oxygen sensor 100a (100b) is greater than 15 MPa. The bonding strength within this range can ensure a strong bond between the protective layer 210a and the oxygen sensor 100a (100b), thereby preventing the protective layer 210a from falling off.

[0134] In some embodiments, the number of interface gaps between the protective layer 210a and the oxygen sensor 100a (100b) is no more than 2, the width of the interface gap along the thickness direction of the oxygen sensor 100a (100b) is approximately less than 5 μm, and the length of the interface gap along the direction perpendicular to the thickness direction is approximately less than 100 μm, so that the protective layer 210a and the oxygen sensor 100a (100b) have good bonding strength.

[0135] The present application provides a method for preparing a sensor element, comprising: S1, ball-milling a mixed ceramic powder, a pore-forming agent, a sintering aid, and a first solvent to obtain a first powder; S2, drying the first powder and sieving it to obtain a second powder; S3, grinding and mixing the second powder with a dispersant, a binder, and a second solvent to obtain a protective layer slurry; S4, coating the protective layer slurry on an oxygen sensor to obtain a sensor element green body; S5, sintering the sensor element green body.

[0136] Step S1 is the preparation of the first powder, that is, using a ball milling mixing method to uniformly mix the ceramic powder, the pore former, the sintering aid and the first solvent.

[0137] Ceramic powder is the primary raw material for preparing protective layer 210a. When preparing protective layer 210a, the ceramic powder is typically mixed with other raw materials and applied to the surface of the oxygen sensor. By adjusting the raw material formula and process parameters, the thickness, porosity, and other performance indicators of the protective layer can be controlled to meet the performance requirements of sensor element 200. In some embodiments, the ceramic powder is one or both of Al2O3 and ZrO2, with a particle size of approximately 0.5 μm to approximately 5 μm. This means that it can be Al2O3, ZrO2, or both. The zirconium oxide can be Y2O3, CeO2, or CaO-stabilized c-ZrO2 (cubic ZrO2), where the molar amount of Y2O3, CeO2, or CaO is approximately 8 mol% to approximately 10 mol%. The Al2O3 can be α-Al2O3 or γ-Al2O3. Ceramic powder exhibits excellent high-temperature resistance, chemical stability, wear resistance, electrical insulation, and dielectric properties. In some embodiments, the ceramic powder is Al2O3 powder having a D50 of 2 μm. In some embodiments, the ceramic powder is ZrO2 powder having a D50 of approximately 3 μm.

[0138] The preparation of the protective layer 210a requires the addition of a pore-forming agent, which is mainly used to adjust the porosity, pore size, and distribution of the protective layer, increase the gas channel, and thus improve the response speed and sensitivity of the sensor. The presence of pores allows the gas to pass through the protective layer 210a better, shortening the path for the gas to reach the electrode, thereby improving the response speed of the sensor. When there is too much pore-forming agent, the adhesion of the protective layer 210a is reduced, and the protective layer is easy to fall off. In some embodiments, the pore-forming agent is one or more of graphite, polymethyl methacrylate, starch, and polyimide resin, with a particle size of about 1 μm to about 5 μm. The above-mentioned pore-forming agent will volatilize or decompose during the sintering process, leaving holes. In some embodiments, the pore-forming agent is graphite powder with a D50 of about 3 μm.

[0139] The addition of sintering aids is mainly used to promote the sintering of the protective layer 210a material and reduce the sintering temperature. When preparing the protective layer 210a, it is usually necessary to mix various raw materials, and make the raw materials melt, flow and form a hard protective layer 210a by high-temperature sintering. Sintering aids can promote mutual diffusion and melting between raw materials, reduce the sintering temperature, and enable the raw materials to fully melt and flow at a lower temperature. At the same time, sintering aids can also improve the wettability between raw materials, promote the diffusion of gas between raw materials, and facilitate the formation and distribution of pores in the protective layer. In some embodiments, the sintering aid includes MgO and SiO2 and substance M, and substance M includes one of CaCO3, TiO2 or Al2O3. The above-mentioned sintering aids begin to melt at a lower temperature. Based on the total mass of the sintering aid, the sintering aid includes approximately 20wt% to approximately 40wt% of MgO, approximately 30wt% to approximately 45wt% of SiO2 and approximately 15wt% to approximately 40wt% of substance M, and the mass ratio of MgO, SiO2 and substance M in the sintering aid is approximately (0.4~1.5):1:(0.3~1.5).

[0140] In other words, the sintering aid combination can be MgO, SiO2, and CaCO3; MgO, SiO2, and TiO2; or MgO, SiO2, and Al2O3. All three combinations can melt at approximately 1000°C to 1300°C, resulting in a molten state of MgO-SiO2-CaO, MgO-SiO2-TiO2, or MgO-SiO2-Al2O3 three-phase coexistence, thereby reducing the sintering temperature.

[0141] If MgO, SiO2 and CaCO3 are used as sintering aids, based on the total mass of the sintering aids, the above-mentioned sintering aids include approximately 15 parts to approximately 35 parts of CaCO3, approximately 30 parts to approximately 45 parts of SiO2 and approximately 25 parts to approximately 40 parts of MgO; if MgO, SiO2 and TiO2 are used as sintering aids, based on the total mass of the sintering aids, the above-mentioned sintering aids include approximately 15 parts to approximately 35 parts of TiO2, approximately 30 parts to approximately 40 parts of SiO2 and approximately 30 parts to approximately 40 parts of MgO; if MgO, SiO2 and Al2O3 are used as sintering aids, based on the total mass of the sintering aids, the above-mentioned sintering aids include approximately 15 parts to approximately 40 parts of Al2O3, approximately 35 parts to approximately 45 parts of SiO2 and approximately 15 parts to approximately 35 parts of MgO.

[0142] The first solvent in step S1 is used to thoroughly mix the ceramic powder, pore-forming agent, and sintering aid by ball milling. The first solvent can be anhydrous ethanol, pure water, or methanol. The first solvent evaporates during the subsequent drying process in step S2 and is no longer present in the second powder. In some embodiments, the first solvent is anhydrous ethanol.

[0143] Step S2 is to dry the first powder mixed evenly by ball milling in step S1, and then pass it through a 50-mesh sieve to obtain a second powder. The second powder includes ceramic powder, pore former and sintering aid.

[0144] In step S3, the dried second powder is ground and mixed with a dispersant, a binder, and a second solvent using a three-roll mill to prepare a protective layer slurry. The prepared protective layer slurry has a viscosity of approximately 10,000 mPa·s to approximately 30,000 mPa·s. A slurry viscosity within this range facilitates coating. A viscosity that is too high may result in a slurry that is too thick, making it difficult to coat and form a film of uniform thickness. A viscosity that is too low may result in a slurry that is too thin, prone to flow, and produces an uneven coating. In some embodiments, the prepared protective layer slurry has a viscosity of 26,000 mPa·s.

[0145] Dispersants can evenly disperse solid particles in the raw material, preventing agglomeration or adhesion between particles. During the preparation process, dispersants can also increase the suspension capacity of solid particles, allowing them to be more stably suspended in the liquid, facilitating the preparation of a more uniform protective layer slurry. In some embodiments, the dispersant is one or more of triolein, polyvinyl butyral, triethanolamine, and castor oil. In some embodiments, the dispersant is triolein.

[0146] The binder is primarily used to bond the dispersed ceramic particles together, forming a stable protective layer and improving its strength and durability. Furthermore, the binder acts as a lubricant, reducing friction between the ceramic particles, making the protective layer smoother and reducing surface defects. In some embodiments, the binder is one or more of ethyl cellulose, polyacrylic acid, and ethylene. In some embodiments, the binder is ethyl cellulose.

[0147] The second solvent is used to fully dissolve the second powder, dispersant, and binder, allowing the solid particles to be evenly dispersed in the slurry, which helps to produce a more stable protective layer. It can also adjust the viscosity of the protective layer slurry. In some embodiments, the second solvent is one of terpineol, toluene, or xylene. In one embodiment of the present application, the second solvent is terpineol.

[0148] The protective layer slurry prepared as above includes, based on its total mass, approximately 60wt% to approximately 80wt% of ceramic powder, approximately 5wt% to approximately 10wt% of a sintering aid, approximately 1wt% to approximately 5wt% of a pore former, approximately 0.1wt% to approximately 2wt% of a dispersant, approximately 0.5wt% to approximately 5wt% of a binder and approximately 15wt% to approximately 25wt% of a second solvent.

[0149] In step S4, the protective layer slurry is applied to the oxygen sensor 100a (100b). The coating can be performed by dip-coating, spin coating, die coating, or screen printing. The thickness of the protective layer is approximately 300 μm to 800 μm, thereby obtaining a green sensor element. This application does not limit the specific coating method; any commonly used method in the art can be used.

[0150] The sintering in step S5 is a one-step sintering method, that is, after the sensor element green body is put into the furnace, it is first heated at a heating rate of about 0.2°C / min to about 0.5°C / min to about 500°C to complete the degreasing process; then the product does not need to be taken out of the furnace, but is continued to be heated at a heating rate of about 0.2°C / min to about 0.5°C / min to about 800°C to remove the pore-forming agent; finally, the protective layer is sintered at a heating rate of about 0.5°C / min to about 1.5°C / min to about 1100°C to about 1300°C, and the holding time is about 1h to about 2h, thereby preparing the protective layer. In some embodiments, after the embryonic body enters the furnace, the temperature is first increased to about 500°C at a heating rate of about 0.2°C / min to complete the degreasing process; then, without taking the product out of the furnace, the temperature is continued to be increased to about 800°C at a heating rate of about 0.5°C / min to remove the pore-forming agent; finally, the temperature is increased at a heating rate of about 1°C / min to about 1250°C to sinter the coating.

[0151] The effects of the technical solution of this application are further illustrated below through specific examples.

[0152] Example (1-1)

[0153] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 32 wt% of MgO, 40 wt% of SiO2 and 28 wt% of CaCO3.

[0154] Preparation of protective layer:

[0155] In this embodiment, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and CaCO3 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is sieved through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0156] Example (1-2)

[0157] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 36 wt% of MgO, 36 wt% of SiO2 and 28 wt% of TiO2.

[0158] Preparation of protective layer:

[0159] In this embodiment, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and TiO2 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0160] Example (1-3)

[0161] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 25wt% of MgO, 40wt% of SiO2 and 35wt% of Al2O3.

[0162] Preparation of protective layer:

[0163] In this embodiment, 75g of ZrO2 powder with a D50 of 3μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and Al2O3 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is sieved through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0164] Examples (1-4)

[0165] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 40wt% of MgO, 45wt% of SiO2 and 15wt% of CaCO3.

[0166] Preparation of protective layer:

[0167] In this embodiment, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and CaCO3 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is sieved through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0168] Examples (1-5)

[0169] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 40 wt% of MgO, 45 wt% of SiO2 and 15 wt% of TiO2.

[0170] Preparation of protective layer:

[0171] In this embodiment, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and TiO2 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0172] Examples (1-6)

[0173] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 40wt% of MgO, 45wt% of SiO2 and 15wt% of Al2O3.

[0174] Preparation of protective layer:

[0175] In this embodiment, 75g of ZrO2 powder with a D50 of 3μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 5wt% of the ceramic powder. MgO, SiO2 and Al2O3 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is sieved through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then the powder is degreased and sintered in a furnace. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0176] Comparative Example (1-1)

[0177] No sintering aids are added.

[0178] Preparation of protective layer:

[0179] In this comparative example, 75g of ZrO2 powder with a D50 of 3μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 2wt% of the ceramic powder. No sintering aid is added, and anhydrous ethanol is used as the first solvent. The above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein, and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. Using the mold method, the slurry is coated on the periphery of the sensor element detection part, and the protective layer thickness is 600μm, and then it is put into the furnace for degreasing and sintering. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0180] Comparative Example (1-2)

[0181] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 100wt% of SiO2.

[0182] Preparation of protective layer:

[0183] In this comparative example, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 0.5wt% of the ceramic powder. 8g of SiO2 is used as a sintering aid, and anhydrous ethanol is used as the first solvent. The above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein, and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll grinder to finally obtain a slurry with a viscosity of 26000mPa·s. Using the mold method, the slurry is coated on the periphery of the sensor element detection part, and the protective layer thickness is 600μm, and then it is put into the furnace for degreasing and sintering. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0184] Comparative Examples (1-3)

[0185] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 50 wt% of MgO and 50 wt% of SiO2.

[0186] Preparation of protective layer:

[0187] In this comparative example, 75g of Al2O3 powder with a D50 of 2μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 1wt% of the ceramic powder. MgO and SiO2 are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein, and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll grinder to finally obtain a slurry with a viscosity of 26000mPa·s. Using the mold method, the slurry is coated on the periphery of the sensor element detection part, and the protective layer thickness is 600μm, and then it is put into the furnace for degreasing and sintering. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0188] Comparative Examples (1-4)

[0189] Composition of the sintering aid: based on the total weight of the sintering aid, it includes 40 wt% of SiO2 and 60 wt% of Al2O3.

[0190] Preparation of protective layer:

[0191] In this comparative example, 75g of ZrO2 powder with a D50 of 3μm is used as ceramic powder, 4g of graphite powder with a D50 of 3μm is used as a pore-forming agent, and the graphite powder accounts for 2wt% of the ceramic powder. SiO2 and MgO are used as sintering aids, and the total amount of sintering aids is 8g. Anhydrous ethanol is used as the first solvent, and the above raw materials are mixed evenly using a ball mill. After drying and removing the anhydrous ethanol, the powder is passed through a 50-mesh sieve. 1.5g of binder ethyl cellulose, 1g of dispersant triolein, and 20.5g of the second solvent terpineol are added to the sieved powder, and the raw materials are mixed evenly using a three-roll mill to finally obtain a slurry with a viscosity of 26000mPa·s. The slurry is coated on the periphery of the sensor element detection part using the immersion pulling method, and the protective layer thickness is 400μm, and then it is put into the furnace for degreasing and sintering. The degreasing sintering in this embodiment is a one-step sintering method, that is, after the blank is put into the furnace, the temperature is first raised to 500°C at a heating rate of 0.2°C / min to complete the degreasing process; then the product does not need to be taken out of the furnace, but continues to be heated to 800°C at a heating rate of 0.5°C / min to remove the pore-forming agent; finally, the temperature is raised to 1250°C at a heating rate of 1°C / min to sinter the coating, and the holding time is 2 hours.

[0192] Performance Testing

[0193] (1) Test of bonding strength between protective layer and oxygen sensor

[0194] The bonding strength of each embodiment and comparative example was tested on a universal testing machine using a homemade fixture. The test results are shown in Table 1.

[0195] Cross-sectional electron micrograph of the protective layer

[0196] The cross-sectional electron micrographs of the protective layers of Example (1-3), Comparative Example (1-1), Comparative Example (1-2) and Comparative Example (1-4) were observed, and the results are shown in Figures 10 to 13.

[0197] Table 1

[0198] Figure 10 is an electron micrograph of a cross-section of the protective layer of Examples (1-3) of the present application. The image shows that the protective layer and the oxygen sensor in this example are tightly bonded, with fewer than two gaps greater than 5 μm in width and no gaps greater than 100 μm in length along the oxygen sensor.

[0199] As shown in Figures 11-13, Figures 11-13 are cross-sectional electron micrographs of the protective layer of Comparative Examples (1-1), (1-2), and (1-4), respectively. In all of these comparative examples, multiple, relatively obvious gaps of varying degrees existed between the protective layer and the oxygen sensor, indicating a loose fit between the protective layer and the oxygen sensor.

[0200] Combined with the results of the bonding strength test, the bonding strength between the protective layer 210a and the oxygen sensor 100a (100b) in each embodiment is better than that in the comparative example. The protective layer 210a prepared by using the mixed sintering aid improves the bonding strength between the protective layer and the oxygen sensor 100a (100b).

[0201] In some embodiments, as shown in Figures 14-16, the sensor element 200b provided in the present application includes the oxygen sensor 100a (100b) described above, and a protective layer (210b) at least partially covering the oxygen sensor 100a (100b), wherein the protective layer 210b includes an inner protective layer 211, an intermediate protective layer 212, and an outer protective layer 213 stacked in sequence; the inner protective layer 211 is close to the oxygen sensor 100a (100b), and the outer protective layer 213 is away from the oxygen sensor 100a (100b); the thermal expansion coefficient of the inner protective layer 211 is α1, and the thermal expansion coefficient of the oxygen sensor 100a (100b) is α, satisfying α<α1<13×10 -6 ·k -1 If the thermal expansion coefficient of the internal protective layer 211 is smaller than the thermal expansion coefficient of the oxygen sensor 100a (100b), fatigue cracks are likely to occur in the internal protective layer 211 as the heating cycle of the sensing element 200b increases.

[0202] In this embodiment, the thermal expansion coefficients α1, α2, and α3 of the inner protective layer 211, the middle protective layer 212, and the outer protective layer 213 satisfy α3<α2<α1; at the same time, if the thermal expansion coefficient α2 of the middle protective layer 212 is greater than the thermal expansion coefficient α of the oxygen sensor 100a (100b), the middle protective layer 212 will expand more, thereby generating shear stress inside the middle protective layer 212. In order to avoid the above situation, the thermal expansion coefficients of the oxygen sensor 100a (100b), the inner protective layer 211, the middle protective layer 212, and the outer protective layer 213 satisfy α3<α2<α<α1<13×10 -6 ·k -1This is because if the thermal expansion coefficient of the protective layer 210b is the same from the inside to the outside, when the outer protective layer 213 located on the outside of the protective layer 210b encounters water impact and the temperature drops suddenly, it will cause a large contraction; while the inner protective layer 211 located on the inside of the protective layer 210b contacts the oxygen sensor 100a (100b), absorbs the heat transferred from the oxygen sensor 100a (100b) to the outside, and will produce a large degree of expansion. At this time, the difference in expansion and contraction between the inside and outside of the protective layer 210b is large, the stress is unbalanced, and it is very easy to crack inside the protective layer 210b. Therefore, when the thermal expansion coefficients of the oxygen sensor 100a (100b), the inner protective layer 211, the middle protective layer 212 and the outer protective layer 213 satisfy α3<α2<α<α1<13×10 -6 ·k -1 When the thermal expansion coefficient α1 of the inner protective layer 211 is greater than the thermal expansion coefficient α of the oxygen sensor 100a (100b), the protective layer 210b can expand synchronously with the oxygen sensor 100a (100b) or maintain a similar expansion trend during the temperature increase of the sensing element 200b, thereby avoiding compressive stress on the protective layer 210b due to the expansion trend of the oxygen sensor 100a (100b) being greater than the expansion trend of the protective layer 210b; the thermal expansion coefficient α3 of the outer protective layer 213 should be less than that of the oxygen sensor 100a (100b). The thermal expansion coefficient α, so that the protective layer 210b only shrinks slightly when it is impacted by condensation water; the middle protective layer 212 is the buffer area of ​​the protective layer 210b, and the thermal expansion coefficient α2 of the buffer area should be between the expansion coefficient α1 of the inner protective layer 211 and the expansion coefficient α3 of the outer protective layer 213, so that the expansion and contraction of the inner and outer sides of the protective layer 210b are buffered in its middle part, so that the protective layer 210b as a whole achieves temperature and thermal stress balance, and the protective layer 210b has good stability and protection.

[0203] In this embodiment, the thermal expansion coefficient α1 of the inner protective layer 211 is at most 3×10 -6 ·k -1 , that is, the difference between the thermal expansion coefficient α1 of the inner protective layer 211 and the thermal expansion coefficient α of the oxygen sensor 100b is approximately less than 3×10 -6 ·k -1By controlling the difference in thermal expansion coefficients between the inner protective layer 211 and the oxygen sensor 100a (100b), the thermal expansion coefficient of the inner protective layer 211 is slightly greater than that of the oxygen sensor 100a (100b). This allows the expansion trends of the inner protective layer 211 and the oxygen sensor 100a (100b) to be consistent, while also protecting the inner protective layer 211 from compressive stress caused by the expansion of the oxygen sensor 100a (100b). The thermal expansion coefficient of the inner protective layer 211 should also not be too large, otherwise the expansion trend of the inner protective layer 211 will be significantly greater than the expansion trend of the oxygen sensor 100a (100b), generating tensile stress within the inner protective layer 211, which may cause the inner protective layer 211 to rupture or peel off from the oxygen sensor 100a (100b).

[0204] Furthermore, the protective layer 210b should have an appropriate thickness to provide some cushioning for expansion or contraction. Secondly, once applied to the sensor element 200b, the protective layer 210b increases the overall thermal mass of the sensor element 200b. Therefore, the protective layer 210b should not be too thick, as this will prolong the ignition time of the sensor element 200b. In this embodiment, the total thickness of the protective layer 210b is approximately less than 1 mm, with the thicknesses of both the inner protective layer 211 and the outer protective layer 213 being approximately less than 300 μm, and the thickness of the intermediate protective layer 212 being approximately less than 400 μm. A thickness within this range contributes to good performance of the gas sensor element.

[0205] The buffer zone within protective layer 210b, or the intermediate protective layer 212, is designed to balance the differential expansion and contraction and temperature differences between the inside and outside of protective layer 210b. This balances the thermal stresses generated within protective layer 210b, thereby improving the stability of protective layer 210b and providing it with excellent protective properties. The buffer zone within protective layer 210b can be divided into several layers with different thermal expansion coefficients. The more layers there are, the more significant the buffering effect will be. However, too many layers will make the manufacturing of protective layer 210b more complex and difficult. Therefore, to ensure that protective layer 210b has better performance, the intermediate protective layer 210b should have no fewer than two layers, that is, the total number of layers of protective layer 210b should be no fewer than four. This avoids significant manufacturing difficulties and allows the thermal stresses inside and outside protective layer 210b to be balanced in the intermediate protective layer 212, thereby improving the stability of protective layer 210b and its protective properties.

[0206] In this embodiment, as shown in FIG16 , the intermediate protective layer 212 includes at least two sublayers, that is, the protective layer 210b comprises at least a four-layer structure. In some embodiments, the intermediate protective layer 212 includes two sublayers, namely, the protective layer 210b includes an inner protective layer 211, a first intermediate protective layer 2121, a second intermediate protective layer 2122, and an outer protective layer 213. Furthermore, the thermal expansion coefficient α4 of the first intermediate protective layer 2121 should be greater than the thermal expansion coefficient α5 of the second intermediate protective layer 2122. The thickness of the inner protective layer 211 and the outer protective layer 213 is approximately less than 300 μm; the thickness of the first intermediate protective layer 2121 and the second intermediate protective layer 2122 is approximately less than 200 μm. After being buffered by the first intermediate protective layer 2121 and the second intermediate protective layer 2122, the difference in expansion or contraction between the internal protective layer 211 and the external protective layer 213 has become very small. In this case, the protective layer 210b will not produce cracks due to inconsistent contraction or expansion between the inside and the outside, thereby improving the stability and protection of the protective layer 210b.

[0207] In some embodiments, as shown in FIG16 , the protective layer 210b includes at least one layer having a porous structure. In some implementations, the inner protective layer 211, the first intermediate protective layer 2121, the second intermediate protective layer 2122, and the outer protective layer 213 of the protective layer 210b each have a porous structure, with the porosity of each layer decreasing as it moves away from the oxygen sensor 100a (100b). The inner protective layer 211 has a porosity of approximately 30% to approximately 60%, the first intermediate protective layer 2121 has a porosity of approximately 30% to approximately 50%, the second intermediate protective layer 2122 has a porosity of approximately 20% to approximately 40%, and the outer protective layer 213 has a porosity of approximately 15% to approximately 30%. This structure optimizes gas transmission within the protective layer 210b, allowing gas to more efficiently pass through the protective layer 210b and participate in the electrochemical reaction. Furthermore, this design improves the corrosion resistance of the protective layer 210b, extending the service life of the gas sensor element.

[0208] Furthermore, in this embodiment, the material of the inner protective layer 211 can be at least one of zirconium oxide, aluminum titanate, or forsterite; the material of the intermediate protective layer 212 (i.e., the first intermediate protective layer 2121 and the second intermediate protective layer 2122) can be at least one of magnesia-aluminum spinel, andalusite, or alumina; and the material of the outer protective layer 213 can be at least one of mullite, zircon, or cordierite. Different materials have different thermal expansion coefficients. This application does not specifically limit the material of the protective layer 210b and can be adjusted according to actual needs.

[0209] In some embodiments, as shown in Figures 14 and 15, the sensing element 200 includes an oxygen sensor 100a (100b) and a protective layer 210b that at least partially covers the surface of the oxygen sensor 100a (100b). The sensing element 200b includes a functional area consisting of a detection unit and a heating unit having at least a pair of electrodes on a solid electrolyte matrix, and the surface of the portion outside the functional area that contacts the gas detection channel 80 is covered with a protective layer 210b. The functional area is formed by stacking and co-firing the detection unit and the heating unit, and the detection unit includes a pump cell unit and a Nernst cell unit. The protective layer 210b can separate the functional area of ​​the sensing element 200b from the water in the detected gas, preventing the water from contacting the functional area, thereby preventing the sensing element 200b from being subjected to water impact, resulting in cracking of the solid electrolyte matrix or abnormal signal output.

[0210] As shown in FIG15 , in this embodiment, the functional area of ​​the sensor element 200b is composed of a pump cell, a Nernst cell, and a heating cell, including: a test electrode 53c, a first electrolyte layer 11c, a first common electrode 51c, a second electrolyte layer 12c, a second common electrode 52c, a third electrolyte layer 13c, a reference electrode 54c, a fifth electrolyte layer 15c, a heater electrode 55c, an insulating layer 62c, and a sixth electrolyte layer 16b. The test electrode 53c, the first electrolyte layer 11c, and the first common electrode 51c constitute the pump cell; the second common electrode 52c, the third electrolyte layer 13c, and the reference electrode 54c constitute the Nernst cell; and the fifth electrolyte layer 15c, the heater electrode 55c, the insulating layer 62c, and the sixth electrolyte layer 16b constitute the heating cell.

[0211] In this embodiment, the heating unit is used to heat the sensor element 200b, rapidly raising its temperature. The heating electrode 55c is embedded in the insulating layer 62c and connected to an external controller via leads to achieve heating control, rapidly heating the functional area of ​​the sensor element 200b to its normal operating temperature. The insulating layer 62c can be made of aluminum oxide.

[0212] In this embodiment, the first electrolyte layer 11c, the second electrolyte layer 12c, the third electrolyte layer 13c, the fourth electrolyte layer 14c, the fifth electrolyte layer 15c and the sixth electrolyte layer 16c can all be formed by yttrium-doped zirconia or scandium-doped zirconia, and are formed into a solid electrolyte matrix of the sensing element 200b by stacking and co-firing, wherein the molar fraction of yttrium or scandium can optionally be between approximately 3 mol% and approximately 10 mol%.

[0213] In this embodiment, the test electrode 53c, the first common electrode 51c, the second common electrode 52c, the reference electrode 54c, and the heater electrode 55c can all be made of platinum and connected to an external controller via leads. The test electrode 53c contacts the gas being tested, while the reference electrode 54c contacts the atmosphere or a reference gas. Furthermore, since the second common electrode 52c, the third electrolyte layer 13c, and the reference electrode 54c form a Nernst cell, when the oxygen concentration difference between the second common electrode 52c and the reference electrode 54c differs, a potential difference, known as the Nernst potential difference, is generated between the two electrodes. Based on this Nernst potential difference, the pump cell adjusts the pump current under the control of the vehicle's electronic control system, thereby achieving real-time control of the engine's air-fuel ratio.

[0214] The technical solution of this application is described in detail below with reference to specific embodiments.

[0215] Example (2-1)

[0216] A sensing element includes an inner protective layer 211, a first intermediate protective layer 2121, a second intermediate protective layer 2122, and an outer protective layer 213. The thermal expansion coefficient of the oxygen sensor 100a (100b) is 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, and the thermal expansion coefficient is 10.1×10 -6 / ℃, porosity of 50% and thickness of 150μm; the first intermediate protective layer 2121 is alumina, with a porosity of 43% and a thickness of 50μm; the second intermediate protective layer 2122 is magnesium aluminum spinel, with a porosity of 36% and a thickness of 50μm; the outer protective layer 213 is zircon, with a porosity of 28% and a thickness of 150μm.

[0217] Example (2-2)

[0218] A sensing element includes an inner protective layer 211, a first intermediate protective layer 2121, and an outer protective layer 213. The thermal expansion coefficient of the oxygen sensor 100a (100b) is 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, and the thermal expansion coefficient is 10×10 -6 / ℃, porosity of 55%, thickness of 200μm; the first intermediate protective layer 2121 is alumina, with a porosity of 43% and a thickness of 50μm; the outer protective layer 213 is zircon, with a porosity of 28% and a thickness of 200μm.

[0219] Comparative Example (2-1)

[0220] A sensing element without any protective layer applied.

[0221] Comparative Example (2-2)

[0222] A sensing element, including an inner protective layer 211, an oxygen sensor 100a (100b) having a thermal expansion coefficient of 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity is 41%, and thickness is 260μm.

[0223] Comparative Example (2-3)

[0224] A sensing element includes an inner protective layer 211 and an outer protective layer 213. The thermal expansion coefficient of the oxygen sensor 100a (100b) is 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity of 40%, and thickness of 200μm; the outer protective layer 213 is zircon, with a porosity of 26% and a thickness of 100μm.

[0225] Comparative Example (2-4)

[0226] A sensing element includes an inner protective layer 211, a first intermediate protective layer 2121, a second intermediate protective layer 2122, and an outer protective layer 213. The thermal expansion coefficient of the oxygen sensor 100a (100b) is 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, with a thermal expansion coefficient of 9.8×10 -6 / ℃, porosity of 60% and thickness of 300μm; the first intermediate protective layer 2121 is alumina, with a porosity of 50% and a thickness of 200μm; the second intermediate protective layer 2122 is magnesium aluminum spinel, with a porosity of 40% and a thickness of 200μm; the outer protective layer 213 is zircon, with a porosity of 30% and a thickness of 300μm.

[0227] Comparative Example (2-5)

[0228] A sensing element includes an inner protective layer 211, a first intermediate protective layer 2121, a second intermediate protective layer 2122, and an outer protective layer 213. The thermal expansion coefficient of the oxygen sensor 100a (100b) is 9.6×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, and the thermal expansion coefficient is 10.3×10 -6 / ℃, porosity of 30% and thickness of 400μm; the first intermediate protective layer 2121 is alumina, with a porosity of 30% and a thickness of 220μm; the second intermediate protective layer 2122 is magnesium aluminum spinel, with a porosity of 20% and a thickness of 210μm; the outer protective layer 213 is zircon, with a porosity of 15% and a thickness of 400μm.

[0229] Comparative Example (2-6)

[0230] A gas sensing element includes an inner protective layer 211, and an oxygen sensor 100a (100b) has a thermal expansion coefficient of 10.3×10 -6 / ℃; the inner protective layer 211 is zirconium oxide, with a thermal expansion coefficient of 9.7×10 -6 / ℃, porosity is 60%, and thickness is 260μm.

[0231] To demonstrate the beneficial effects of the present application, the following performance tests were performed on the gas sensor elements of the above embodiments and comparative examples:

[0232] (1) Water shock test

[0233] The basis for judging the failure of the protective layer during the working phase of the sensor element:

[0234] A 12V DC power supply is applied to the heating unit to heat the sensor element. After 1 minute, the sensor element stabilizes and about 50μL of water is sprayed onto the protective layer of the sensor element. The internal resistance of the sensor element is then measured. If the internal resistance exceeds a variation range of 5%, it is determined that cracks have occurred in the solid electrolyte body of the sensor element. The number of water sprays when the cracks occur is recorded, which is the effective number of times the sensor element resists water shock.

[0235] The test results are shown in Table 2, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0236] (2) Ignition time test

[0237] Ignition time refers to the time it takes for a sensor element to heat up and reach a stable working state. Generally speaking, the thicker the protective layer of the sensor element, the longer the ignition time.

[0238] The test results are shown in Table 2, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0239] (3) Protective layer peeling test

[0240] The sensor element was mounted on a test bench. A 14V DC voltage was applied for 1 minute during each thermal cycle, followed by a 2-minute air cooling period. After 5000 thermal cycles, a drop test was performed. The drop height was 500mm, and the surface was concrete. The sensor element was dropped with its length parallel to the ground. The number of drops until the protective layer fell off was recorded.

[0241] The test results are shown in Table 3, where √ represents that the sample has this layer, and × represents that the sample does not have this layer.

[0242] Table 2

[0243] Table 3

[0244] The above results show that the test results of each embodiment are good, the water shock resistance is strong, the ignition time is short, and the stability is significantly better than the comparative example. The sensor element 200 of the present application has good stability.

[0245] Furthermore, an embodiment of the present application further provides an engine 300. Referring to FIG17 , the engine 300 includes: any one of the above-mentioned oxygen sensors 100a (100b), and / or any one of the above-mentioned sensing elements 200a (200b). For example, the engine 300 may include an exhaust pipe, and the oxygen sensor 100a (100b) and / or the sensing element 200a (200b) may be disposed in the exhaust pipe of the engine 300 to detect the oxygen concentration in the engine exhaust.

[0246] In addition, an embodiment of the present application further provides a vehicle 400. Referring to FIG18 , the vehicle 400 includes: any one of the above-mentioned oxygen sensors 100a (100b), and / or any one of the above-mentioned sensing elements 200a (200b), and / or any one of the above-mentioned engines 300. Exemplarily, the oxygen sensor 100a (100b) and / or the sensing element 200a (200b) can be disposed in the cabin of the vehicle 400 to detect the oxygen concentration in the cabin. Exemplarily, when the vehicle 400 includes any one of the above-mentioned engines 300, the vehicle 400 can be, for example, but not limited to, a fuel vehicle, a hybrid vehicle, or the like.

[0247] Description of reference numerals in Figures 1 and 2:

[0248] 1. Gas channel to be tested; 2. Diffusion barrier unit; 3. Detection cavity.

[0249] Description of reference numerals in Figures 3 and 4:

[0250] 100a, oxygen sensor; 101, upper surface of oxygen sensor; 102, lower surface of oxygen sensor;

[0251] 11a, first electrolyte layer; 12a, second electrolyte layer; 13a, third electrolyte layer; 14a, fourth electrolyte layer; 15a, fifth electrolyte layer; 16a, sixth electrolyte layer;

[0252] 20a, diffusion barrier structure; 21, first end surface; 22, second end surface;

[0253] 30a, detection cavity; 31, first cavity wall; 32, second cavity wall;

[0254] 40a, reference chamber; 41, third chamber wall; 42, fourth chamber wall;

[0255] 51a, first common electrode; 52a, second common electrode; 53a, test electrode; 54a, reference electrode; 55a, heating electrode;

[0256] 61a, electrode protection layer; 62a, insulation layer;

[0257] Description of reference numerals in Figures 5 to 7:

[0258] 100b, oxygen sensor; 11b, first electrolyte layer; 12b, second electrolyte layer; 13b, third electrolyte layer; 14b, fourth electrolyte layer; 15b, fifth electrolyte layer; 17, electrolyte cover layer;

[0259] 20b, diffusion barrier structure;

[0260] 30b, detection cavity;

[0261] 40b, reference cavity;

[0262] 51b, first common electrode; 52b, second common electrode; 53b, test electrode; 54b, reference electrode; 55b, heating electrode;

[0263] 61b, electrode protection layer; 62b, insulation layer;

[0264] 71, first diffusion channel; 72, second diffusion channel; 73, third diffusion channel;

[0265] Description of reference numerals in Figures 8 to 13:

[0266] 100a, oxygen sensor; 100b, oxygen sensor;

[0267] 200a, sensing element; 210a, protective layer;

[0268] Description of reference numerals in Figures 14 to 16:

[0269] 11c, first electrolyte layer; 12c, second electrolyte layer; 13c, third electrolyte layer; 14c, fourth electrolyte layer; 15c, fifth electrolyte layer; 16b, sixth electrolyte layer;

[0270] 20c, diffusion barrier structure;

[0271] 30c, detection cavity;

[0272] 40c, reference cavity;

[0273] 51c, first common electrode; 52c, second common electrode; 53c, test electrode; 54c, reference electrode; 55c, heating electrode;

[0274] 62c, insulation layer;

[0275] 80. Gas detection channel;

[0276] 100a, oxygen sensor; 100b, oxygen sensor;

[0277] 200b, sensing element; 210a, protective layer; 211, inner protective layer; 212, intermediate protective layer; 2121, first intermediate protective layer; 2122, second intermediate protective layer; 213, outer protective layer;

[0278] Description of reference numerals in FIG. 17 and FIG. 18

[0279] 100a, oxygen sensor; 100b, oxygen sensor;

[0280] 200a, sensing element; 200b, sensing element;

[0281] 300, engine;

[0282] 400. Vehicle.

Claims

1. An oxygen sensor (100a), comprising: Stacked first electrolyte layer (11a) and second electrolyte layer (12a), wherein a detection cavity (30a) is provided in the second electrolyte layer (12a); A diffusion barrier structure (20a), at least partially penetrating through the first electrolyte layer (11a) and communicating with the detection cavity (30a); Wherein, on the side of the diffusion barrier structure (20a) away from the second electrolyte layer (12a), there is a first end face (21), and the first end face (21) is flush with or protrudes from the surface of the first electrolyte layer (11a) facing away from the second electrolyte layer (12a).

2. The oxygen sensor (100a) according to claim 1, wherein, The diffusion barrier structure (20a) also extends into the detection cavity (30a).

3. The oxygen sensor (100a) according to claim 1 or 2, wherein, The detection cavity (30a) has a first cavity wall (31) and a second cavity wall (32) opposite in position, wherein the first cavity wall (31) is located on the surface of the first electrolyte layer (11a) facing the second electrolyte layer (12a); The diffusion barrier structure (20a) also has a second end face (22), and the second end face (22) abuts against the second cavity wall (32) of the detection cavity (30a).

4. The oxygen sensor (100a) according to any one of claims 1 to 3, wherein, The diffusion barrier structure (20a) is a diffusion barrier column.

5. The oxygen sensor (100a) according to claim 4, wherein, The extending direction of the diffusion barrier column is substantially parallel to the stacking direction of the first electrolyte layer (11a) and the second electrolyte layer (12a).

6. The oxygen sensor (100a) according to any one of claims 1 to 5, wherein, A test electrode (53a) is provided on the surface of the first electrolyte layer (11a) facing away from the second electrolyte layer (12a), a common electrode is provided in the detection cavity (30a), and the pump cell of the oxygen sensor (100a) includes the test electrode (53a) and the common electrode.

7. The oxygen sensor (100a) according to any one of claims 1 to 6, further comprising a reference cavity (40a) for accommodating a reference gas, a reference electrode (54a) is provided in the reference cavity, and the Nernst cell of the oxygen sensor (100a) includes the reference electrode (54a) and the common electrode.

8. The oxygen sensor according to claim 7, further comprising: A third electrolyte layer (13a), stacked on the surface of the second electrolyte layer (12a) facing away from the first electrolyte layer (11a); A fourth electrolyte layer (14a), stacked on the surface of the third electrolyte layer (13a) facing away from the second electrolyte layer (12a); the reference cavity (40a) is provided in the fourth electrolyte layer (14a); Wherein, the reference cavity (40a) has a third cavity wall (41) and a fourth cavity wall (42) opposite in position, the third cavity wall (41) is located on the surface of the third electrolyte layer (13a) facing the fourth electrolyte layer (14a), and the reference electrode (54a) is provided on the third cavity wall (41).

9. The oxygen sensor according to claim 8 further comprises: A heating layer for heating, the heating layer is stacked on the surface of the fourth electrolyte layer (14a) facing away from the third electrolyte layer (13a); Wherein, the total thickness of the heating layer and the fourth electrolyte layer (14a) is approximately equal to the total thickness of the first electrolyte layer (11a), the second electrolyte layer (12a), and the third electrolyte layer (13a).

10. A method for manufacturing an oxygen sensor for manufacturing the oxygen sensor (100a) according to any one of claims 1 to 9, comprising: Forming a detection cavity (30a) in the second electrolyte layer (12a); Stacking the first electrolyte layer (11a) and the second electrolyte layer (12a); Forming a diffusion barrier structure (20a) at least partially penetrating the first electrolyte layer (11a); the diffusion barrier structure (20a) communicates with the detection cavity (30a); wherein, a first end face (21) is provided on a side of the diffusion barrier structure (20a) away from the second electrolyte layer (12a), and the first end face (21) is flush with or protrudes from a surface of the first electrolyte layer (11a) facing away from the second electrolyte layer (12a).

11. The preparation method according to claim 10 further comprises: Forming a through hole in the first electrolyte layer (11a), and after stacking the first electrolyte layer (11a) and the second electrolyte layer (12a), the through hole communicates with the detection cavity (30a); The step of forming the diffusion barrier structure (20a) at least partially penetrating the first electrolyte layer (11a) includes: forming a diffusion barrier structure (20a) at least filled in the through hole.

12. An oxygen sensor (100b), comprising: Stacked first electrolyte layer (11b), electrolyte covering layer (17), and second electrolyte layer (12b); Wherein, a first diffusion channel (71) is provided in the first electrolyte layer (11b); At least one second diffusion channel (72) is provided in the electrolyte covering layer (17); and the total cross-sectional area of all the second diffusion channels (72) is smaller than the cross-sectional area of the first diffusion channel (71); A diffusion barrier structure (20b) and a detection cavity (30b) are provided in the second electrolyte layer (12b), the diffusion barrier structure (20b) communicates with the first diffusion channel (71) at least through the second diffusion channel (72), and the detection cavity (30b) communicates with the second diffusion channel (72) at least through the diffusion barrier structure (20b).

13. The oxygen sensor (100b) according to claim 12, wherein, Each of the second diffusion channels (72) is opposite to the first diffusion channel (71) in position.

14. The oxygen sensor (100b) according to claim 12 or 13, wherein, A third diffusion channel (73) is provided in the diffusion barrier structure (20b), the third diffusion channel (73) communicates with the first diffusion channel (71) through the second diffusion channel (72), and the third diffusion channel (73) communicates with the detection cavity (30b) through the diffusion barrier structure (20b).

15. The oxygen sensor (100b) according to claim 14, characterized in that, The cross-sectional shape of the diffusion barrier structure (20b) is substantially annular; Among them, the third diffusion channel (73) is a diffusion through-hole at the center of the diffusion barrier structure (20b), and the detection cavity (3Ob) is located outside the diffusion barrier structure (20b).

16. The oxygen sensor (100b) according to claim 14 or 15, wherein, The cross-sectional area of the third diffusion channel (73) is substantially larger than the total cross-sectional area of all the second diffusion channels (72), and each of the second diffusion channels (72) is opposite in position to the third diffusion channel (73).

17. The oxygen sensor (100b) according to any one of claims 14 to 16, wherein, The cross-sectional dimensions of the third diffusion channel (73) are substantially equal to those of the first diffusion channel (71) and they are opposite in cross-sectional position.

18. The oxygen sensor (100b) according to any one of claims 12 to 17, wherein, A receiving through-hole is provided in the second electrolyte layer (12b), and the diffusion barrier structure (20b) and the detection cavity (30b) are provided in the receiving through-hole.

19. The oxygen sensor (100b) according to claim 18, wherein, Each of the second diffusion channels (72) is opposite in position to the diffusion barrier structure (20b), and the space in the receiving through-hole other than the diffusion barrier structure (20b) forms the detection cavity (30b).

20. The oxygen sensor (100b) according to any one of claims 12 to 19, wherein, The first diffusion channel (71) is a diffusion through-hole, and / or the second diffusion channel (72) is a diffusion through-hole.

21. The oxygen sensor (100b) according to any one of claims 13 to 20, wherein, The second diffusion channel (72) is a diffusion slit, the cross-section of the diffusion slit is substantially rectangular, the length of the diffusion slit is about 100 mm to about 300 mm, and the width of the diffusion slit is about 5 mm to about 50 mm.

22. The oxygen sensor (100b) according to any one of claims 12 to 21, wherein, The thickness of the electrolyte covering layer (17) is about 50 μm to about 200 mm.

23. The oxygen sensor (100b) according to any one of claims 12 to 22, wherein, The material of the electrolyte covering layer (17) is zirconia ceramic doped with yttrium oxide or scandium oxide; wherein, the molar mass of yttrium oxide or scandium oxide in the zirconia ceramic is about 3% to about 8%.

24. The oxygen sensor (100b) according to any one of claims 12 to 23, wherein, A test electrode (53b) is provided on the surface of the first electrolyte layer (11b) facing away from the electrolyte covering layer (17), a common electrode is provided in the detection cavity (30b), and the pump cell of the oxygen sensor (100b) includes the test electrode (53b) and the common electrode.

25. The oxygen sensor (100b) according to any one of claims 12 to 24 further includes a reference cavity (40b) for accommodating a reference gas, a reference electrode is provided in the reference cavity, and the Nernst cell of the oxygen sensor includes the reference electrode and the common electrode.

26. The oxygen sensor (100b) according to claim 25, wherein, The reference cavity (40b) is provided in the second electrolyte layer (12b), and the reference cavity (40b) is separated from the detection cavity (30b) by the second electrolyte layer (12b).

27. The oxygen sensor (100b) according to claim 26, wherein, The reference cavity (40b) is a notch at the edge of the second electrolyte layer (12b).

28. A method for manufacturing an oxygen sensor for manufacturing the oxygen sensor (100b) according to any one of claims 12 to 27, including: Forming a first diffusion channel (71) in the first electrolyte layer (11b); Forming a diffusion barrier structure (20b) and a detection cavity (30b) in the second electrolyte layer (12b); Form at least one second diffusion channel (72) in the electrolyte covering layer (17); and the total cross-sectional area of all the second diffusion channels (72) is substantially smaller than the cross-sectional area of the first diffusion channel (71). Stack the first electrolyte layer (11b), the electrolyte covering layer (17), and the second electrolyte layer (12b); the diffusion barrier structure (20b) is connected to the first diffusion channel (71) at least through the second diffusion channel (72), and the detection cavity (30b) is connected to the second diffusion channel (72) at least through the diffusion barrier structure (20b).

29. The preparation method according to claim 28, wherein, Before forming at least one second diffusion channel (72) in the electrolyte covering layer (17), the preparation method further includes: Sinter the stacked first electrolyte layer (11b), the electrolyte covering layer (17), and the second electrolyte layer (12b).

30. A sensing element (200a) includes the oxygen sensor (100a) according to any one of claims 1 to 9 or the oxygen sensor (100b) according to any one of claims 12 to 27, and a protective layer (210a) provided on at least a part of the surface of the oxygen sensor. The protective layer (210a) includes about 85 wt% to about 95 wt% of a ceramic phase and about 5 wt% to about 15 wt% of a bonding phase; the ceramic phase includes one or both of Al2O3 and ZrO2; the bonding phase is a three-phase melt, the first phase includes MgO, the second phase includes SiO2, and the third phase includes one of CaO, TiO2, or Al2O3.

31. The sensing element (200a) according to claim 30, wherein, The mass ratio of the first phase, the second phase, and the third phase is approximately (0.4 to 1.5):1:(0.3 to 1.5).

32. The sensing element (200a) according to claim 30 or 31, wherein, The melting point of the bonding phase is about 1000 °C to about 1300 °C.

33. The sensing element (200a) according to any one of claims 30 to 32, wherein, The porosity of the protective layer (210a) is about 20% to about 40%, and the pore diameter is about 0.2 μm to about 5 μm.

34. The sensing element (200a) according to any one of claims 30 to 33, wherein, The thickness of the protective layer (210a) is about 300 μm to about 800 μm.

35. The sensing element (200a) according to any one of claims 30 to 34, wherein, The distribution of the interface gaps between the protective layer (210a) and the oxygen sensor is no more than 2, and the width of the interface gaps in the thickness direction of the oxygen sensor is substantially less than 5 μm.

36. The sensing element (200a) according to claim 35, characterized in that, In the direction perpendicular to the thickness direction, the length of the interface gaps is substantially less than 100 μm.

37. The sensing element (200a) according to any one of claims 30 to 36, wherein, The bonding strength between the protective layer (210a) and the oxygen sensor is substantially greater than 15 MPa.

38. A method for preparing a sensing element for preparing the sensing element (200a) according to any one of claims 30 to 37, comprising: S1. Ball-mill and mix ceramic powder, pore-forming agent, sintering aid, and a first solvent to obtain a first powder material; S2. Dry the first powder material and then screen it to obtain a second powder material; S3. Grind and mix the second powder material with a dispersant, a binder, and a second solvent to obtain a protective layer slurry; S4. Coat the protective layer slurry on the oxygen sensor to obtain a green body of the sensing element; S5. Sinter the green body of the sensing element.

39. The method for preparing a sensing element according to claim 38, wherein, In step S1, the sintering aid includes MgO, SiO2, and substance M, and the substance M includes one of CaCO3, TiO2, or Al2O3.

40. The method for preparing a sensing element according to claim 38 or 39, wherein, Based on the total mass of the sintering aid, the sintering aid includes approximately 20 wt% to approximately 40 wt% of MgO, approximately 30 wt% to approximately 45 wt% of SiO2, and approximately 15 wt% to approximately 40 wt% of substance M.

41. The method for preparing a sensing element according to claim 39 or 40, wherein, The mass ratio of MgO, SiO2, and substance M in the sintering aid is approximately (0.4 to 1.5):1:(0.3 to 1.5).

42. The method for preparing a sensing element according to any one of claims 38 to 41, wherein, In S1, the ceramic powder is one or both of Al2O3 and ZrO2; The pore-forming agent is one or more of graphite, polymethyl methacrylate, starch, and polyimide resin; The first solvent is one of anhydrous ethanol, pure water, or methanol.

43. The method for preparing a sensing element according to any one of claims 38 to 42, wherein, In S3, the dispersant is one or more of glyceryl trioleate, polyvinyl butyral, triethanolamine, and castor oil; The binder is one or more of ethyl cellulose, polyacrylic acid, and ethylene; The second solvent is one of terpineol, toluene, or xylene.

44. The method for preparing a sensing element according to any one of claims 38 to 43, wherein, In S3, based on the total mass of the protective layer slurry, the protective layer slurry includes approximately 60 wt% to approximately 80 wt% of ceramic powder, approximately 5 wt% to approximately 10 wt% of sintering aid, approximately 1 wt% to approximately 5 wt% of pore-forming agent, approximately 0.1 wt% to approximately 2 wt% of dispersant, approximately 0.5 wt% to approximately 5 wt% of binder, and approximately 15 wt% to approximately 25 wt% of second solvent.

45. The method for preparing a sensing element according to any one of claims 38 to 44, wherein, In S3, the viscosity of the protective layer slurry is approximately 10000 mPa·s to approximately 30000 mPa·s.

46. The method for preparing a sensing element according to any one of claims 38 to 45, characterized in that, In S5, the sintering temperature is approximately 1100 °C to approximately 1300 °C, and the sintering holding time is approximately 1 h to approximately 2 h.

47. A sensing element (200b) comprising an oxygen sensor (100a) according to any one of claims 1 to 9 or an oxygen sensor (100b) according to any one of claims 12 to 27, and a protective layer (210b) at least partially covering the oxygen sensor, the protective layer (210b) including a laminated inner protective layer (211), an intermediate protective layer (212), and an outer protective layer (213); the inner protective layer (211) being close to the oxygen sensor, the outer protective layer (213) being away from the oxygen sensor; the inner protective layer (211) having a coefficient of thermal expansion of α1, and the oxygen sensor having a coefficient of thermal expansion of α, satisfying α < α1 < 13×10 -6 ·k -1 .

48. The sensing element (200b) according to claim 47, wherein, The difference between the coefficient of thermal expansion α1 of the internal protective layer (211) and the coefficient of thermal expansion α of the oxygen sensor is at most 3×10 -6 ·k -1 .

49. The sensing element (200b) according to claim 47 or 48, wherein, The thermal expansion coefficients of the inner protective layer (211), the middle protective layer (212), and the outer protective layer (213) are α1, α2, and α3 respectively, satisfying α3 < α2 < α1.

50. The sensing element (200b) according to any one of claims 47 to 49, wherein, The total thickness of the protective layer (210b) is substantially less than 1 mm.

51. The sensing element (200b) according to any one of claims 47 to 50, wherein, The thicknesses of the inner protective layer (211) and the outer protective layer (213) are both substantially less than 300 μm, and the thickness of the middle protective layer (212) is substantially less than 400 μm.

52. The sensing element (200b) according to any one of claims 47 to 51, wherein, The middle protective layer (212) includes at least two sub-layers.

53. The sensing element (200b) according to claim 52, wherein, The middle protective layer (212) includes a stacked first middle protective layer (2121) and a second middle protective layer (2122); the first middle protective layer (2121) is close to the inner protective layer (211), and the second middle protective layer (2122) is far from the inner protective layer (211).

54. The sensing element (200b) according to claim 53, wherein, The protective layer (210b) includes a stacked inner protective layer (211), a first middle protective layer (2121), a second middle protective layer (2122), and an outer protective layer (213).

55. The sensing element (200b) according to claim 53 or 54, wherein, The thermal expansion coefficient of the first intermediate protective layer (2121) is α4, and the thermal expansion coefficient of the second intermediate protective layer (2122) is α5, where α4 > α5.

56. The sensing element (200b) according to any one of claims 53 to 55, wherein, The thicknesses of the first intermediate protective layer (2121) and the second intermediate protective layer (2122) are both substantially less than 200 μm.

57. The sensing element (200b) according to any one of claims 47 to 56, wherein, At least one layer of the protective layer (210b) has a porous structure.

58. The sensing element according to claim 57, wherein, Each layer of the protective layer (210b) has a porous structure, and the porosity of each layer decreases layer by layer along the direction away from the oxygen sensor.

59. The sensing element according to claim 58, wherein, The porosity of the inner protective layer (211) is approximately 30% to approximately 60%, the porosity of the first intermediate protective layer (2121) is approximately 30% to approximately 50%, the porosity of the second intermediate protective layer (2122) is approximately 20% to approximately 40%, and the porosity of the outer protective layer (213) is approximately 15% to approximately 30%.

60. An engine (300), characterized in that, Comprising: The oxygen sensor (100a) according to any one of claims 1 to 9; And / or, the oxygen sensor (100b) according to any one of claims 12 to 27; And / or, the sensing element (200a) according to any one of claims 30 to 37; And / or, the sensing element (200b) according to any one of claims 47 to 59.

61. A vehicle (400), characterized in that, Comprising: The oxygen sensor (100a) according to any one of claims 1 to 9; And / or, the oxygen sensor (100b) according to any one of claims 12 to 27; And / or, the sensing element (200a) according to any one of claims 30 to 37; And / or, the sensing element (200b) according to any one of claims 47 to 59; And / or, the engine (300) according to claim 60.

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