Oxygen sensor and preparation method of oxygen sensor substrate

Abstract

The invention discloses an oxygen sensor and a preparation method of an oxygen sensor substrate. The oxygen sensor comprises a substrate, the substrate is provided with a zirconium oxide layer, and the zirconium oxide layer comprises Zr, trivalent elements, Nb and Al in terms of elements; the phase of the zirconium oxide layer comprises 96wt%-99.7 wt% of tetragonal phase zirconium oxide, the remaining phase is monoclinic phase zirconium oxide, in the tetragonal phase zirconium oxide, the ratio of the molar content of trivalent element oxide to the total molar content of zirconium oxide, trivalent element oxide and niobium oxide is a, a is equal to 4.5 mol%-5.5 mol%, b is equal to 4.5 mol%-5.5 mol%, and c is equal to 4.5 mol%-5.5 mol%. The ratio of the molar content of niobium oxide to the total molar content of zirconium oxide, trivalent element oxide and niobium oxide is b, and a-b is equal to 4mol%-5mol%; wherein the trivalent elements comprise one or more of Y, Sm, Er, Sc and Nd, and the substrate of the oxygen sensor provided by the invention has relatively good mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oxygen sensors, and more particularly to an oxygen sensor and a preparation method of an oxygen sensor substrate. BACKGROUND

[0002] In the related art, an oxygen sensor generally utilizes a difference in oxygen concentration between the inner and outer sides of a substrate to generate a potential difference, thereby achieving the purpose of detecting oxygen concentration. The substrate of the oxygen sensor is generally prepared by flow casting of zirconia powder stabilized by a stabilizer, and the mechanical properties of the current substrate are poor.

[0003] Therefore, there is a need to provide a new technical solution to solve the above technical problems. SUMMARY

[0004] An object of the present application is to provide a new technical solution for an oxygen sensor.

[0005] According to a first aspect of the present application, an oxygen sensor is provided. The oxygen sensor comprises a substrate, the substrate having a zirconia layer, the zirconia layer comprising, in terms of elements: Zr, a trivalent element, Nb, and Al; and,

[0006] The phase of the zirconia layer comprises: 96wt% to 99.7wt% of tetragonal zirconia, and the remaining phase is monoclinic zirconia, in the tetragonal zirconia, the ratio of the molar content of the trivalent element oxide to the total molar content of zirconia, trivalent element oxide and niobium oxide is a, which satisfies a = 4.5mol% to 5.5mol%, and the ratio of the molar content of niobium oxide to the total molar content of zirconia, trivalent element oxide and niobium oxide is b, which satisfies a-b = 4mol% to 5mol%;

[0007] The trivalent element includes one or more of Y, Sm, Er, Sc, and Nd.

[0008] Optionally, a and b satisfy a-b = 4.3mol% to 4.8mol%.

[0009] Optionally, the trivalent element is Y, and the zirconia layer comprises, in terms of elements: 65.12wt% to 67.91wt% of Zr, 5.91wt% to 6.71wt% of Y, 0.05wt% to 1.21wt% of Nb, and 0.1wt% to 0.93wt% of Al.

[0010] Optionally, the zirconia layer comprises, in terms of elements: 65.65wt% to 67.12wt% of Zr, 5.91wt% to 6.71wt% of Y, 0.06wt% to 0.97wt% of Nb, and 0.041wt% to 0.75wt% of Al.

[0011] Optionally, the phase of the zirconia layer comprises 97wt%-99wt% of tetragonal zirconia, and the rest is monoclinic zirconia.

[0012] Optionally, the oxygen sensor is stacked with multiple layers of the substrate.

[0013] Optionally, the oxygen sensor is stacked with three layers of the substrate, and a heater is arranged between the first substrate and the second substrate, and the heater is electrically connected to the first substrate and the third substrate respectively.

[0014] Optionally, the heater is provided with a first insulating layer at both ends of the first substrate and the second substrate respectively.

[0015] Optionally, the oxygen sensor further comprises a reference electrode, which is installed in the second substrate and electrically connected to the first substrate and the third substrate respectively.

[0016] Optionally, the first substrate is provided with a second insulating layer on the outside, and the second insulating layer avoids the electrode on the first substrate.

[0017] Optionally, the oxygen sensor is stacked with two layers of the substrate, which are a heating layer substrate and a detection layer substrate.

[0018] Optionally, the hardness of the substrate is greater than or equal to 1200Hv, the toughness of the substrate is greater than or equal to 6MPam, the bending strength of the substrate is greater than or equal to 700Mpa, the on-off aging frequency of the substrate is greater than or equal to 8000, and the assembly yield of the substrate is greater than or equal to 80%. 0.5

[0019] According to the second aspect of the present application, a method for preparing the oxygen sensor substrate of the above embodiments is provided. The method comprises:

[0020] adding raw materials to an organic additive for ball milling;

[0021] adding a binder for continuous ball milling to obtain a slurry;

[0022] flowing the slurry into a green body;

[0023] screen printing electrodes on the green body to prepare a green body;

[0024] sintering the green body to prepare the substrate;

[0025] wherein the raw materials comprise zirconia powder, niobium pentoxide powder, trivalent oxide powder and aluminum oxide powder.

[0026] ​The trivalent oxide includes one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide, and neodymium oxide.

[0027] Optionally, the trivalent oxide is yttrium oxide, the total amount of the yttrium oxide powder is X, and 7.5wt%≤X≤8.5wt% is satisfied, and the total amount of the zirconium oxide powder and the yttrium oxide powder is M, and 7wt%≤X-0.85M≤7wt% is satisfied.

[0028] Optionally, the X and the M satisfy 7.3wt%≤X-0.85M≤7.7wt%.

[0029] Optionally, the total amount of the aluminum oxide is Z, and 1≤M:Z≤3 is satisfied.

[0030] Optionally, the Z satisfies 1.5≤M:Z≤2.5.

[0031] One technical effect of the present application is that the substrate of the oxygen sensor has good mechanical properties.

[0032] Other features of the present application, and its particular advantages, will become apparent to those skilled in the art from the following detailed description, together with the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0033] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the application and together with the description, serve to explain the principles of the application.

[0034] Figure 1 is a flowchart of the preparation of the oxygen sensor substrate of the present application. DETAILED DESCRIPTION

[0035] Various example embodiments of the present application will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangements of the steps set forth in these embodiments, numerical expressions, and numerical values are not limiting to the scope of the present application unless otherwise specifically stated.

[0036] The following description of at least one example embodiment is merely illustrative in nature and is in no way limiting to the scope of the application or its applications or uses.

[0037] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein. However, where appropriate, such techniques, methods, and apparatus should be considered as being part of the specification.

[0038] In all examples shown and discussed herein, any specific values should be interpreted as merely illustrative and not as limiting. Thus, other examples of the example embodiments can have different values.

[0039] It should be noted that like numerals and letters refer to like items throughout the several views, and once an item is defined in one view, it need not be discussed further in subsequent views.

[0040] According to one embodiment of the present application, an oxygen sensor is provided. The oxygen sensor comprises a substrate having a zirconia layer. The zirconia layer comprises, in terms of elements, Zr, a trivalent element, Nb, and Al; and the phase of the zirconia layer comprises 96wt%-99.7wt% of tetragonal zirconia, and the rest is monoclinic zirconia, wherein in the tetragonal zirconia, the ratio of the molar content of the trivalent element oxide to the total molar content of zirconia, the trivalent element oxide and niobium oxide is a, which satisfies a = 4.5mol%-5.5mol%, and the ratio of the molar content of niobium oxide to the total molar content of zirconia, the trivalent element oxide and niobium oxide is b, which satisfies a-b = 4mol%-5mol%; wherein the trivalent element comprises one or more of Y (yttrium), Sm (samarium), Er (erbium), Sc (scandium), and Nd (neodymium).

[0041] In this example, the substrate of the oxygen sensor of the present application has better mechanical properties, including significantly improved toughness and average bending strength, and the number of times of on-off aging of the substrate is significantly improved, and the assembly yield of the substrate is also significantly improved.

[0042] For example, a can be 4.7mol%, 4.9mol%, 5.4mol%, etc. Further, a and b satisfy a-b = 4.3mol%-4.8mol%. For example, a-b can be 4.3mol%, 4.4mol%, 4.5mol%, 4.6mol%, 4.7mol%, 4.8mol%, etc. Those skilled in the art can determine according to the actual situation, which is not limited here.

[0043] In this example, the hardness of the substrate is greater than or equal to 1200Hv, the toughness of the substrate is greater than or equal to 6MPam 0.5 , the bending strength of the substrate is greater than or equal to 700Mpa, the number of times of on-off aging of the substrate is greater than or equal to 8000, and the assembly yield of the substrate is greater than or equal to 80%.

[0044] In one example, the trivalent element is Y, and the zirconia layer comprises, in terms of elements, 65.12wt%-67.91wt% of Zr, 5.91wt%-6.71wt% of the trivalent element, 0.05wt%-1.21wt% of Nb, and 0.1wt%-0.93wt% of Al.

[0045] For example, if the trivalent element in the zirconia layer is Y, the prepared sample will be subjected to high-energy XRF detection, specifically, the elemental content of the polished sample will be tested using an energy-dispersive X-ray fluorescence spectrometer (EDX-7000). The elemental content will be: Zr 67.5 wt%, Y 6.4 wt%, Nb 0.5 wt%, and Al 0.2 wt%.

[0046] The prepared sample was subjected to XRD to determine the phase composition, that is, the phase composition was determined by X-ray diffraction, including: tetragonal zirconia 98 wt% and monoclinic zirconia 2 wt%.

[0047] Of course, the specific content of each element in the zirconium oxide layer can be determined by those skilled in the art based on the actual situation, and no specific limitation is made here.

[0048] In one example, the zirconium oxide layer contains, by elemental composition: 65.65 wt% - 67.12 wt% Zr, 5.91 wt% - 6.71 wt% trivalent elements, 0.06 wt% - 0.97 wt% Nb, and 0.041 wt% - 0.75 wt% Al.

[0049] In this example, the aforementioned elemental ratio can further improve the hardness, toughness, and average bending strength of the oxygen sensor, and the substrate produced also has a greater average number of on / off aging cycles.

[0050] In one example, the phase composition of the oxygen sensor comprises: the phase composition of the zirconia layer comprises: 97wt%-99wt% tetragonal zirconia, with the remainder being monoclinic zirconia.

[0051] In this example, the aforementioned phase ratio can further improve the hardness, toughness, and average bending strength of the oxygen sensor, and the substrate produced also has a greater average number of on / off aging cycles.

[0052] In this example, the oxygen sensor may also contain other phases, but this has no negative impact on the oxygen sensor of the present invention. In the present invention, the phases contained in the oxygen sensor are defined with the above-mentioned content as a reference for the oxygen sensor. The elemental composition of the oxygen sensor may also contain other elements, such as oxygen.

[0053] In one example, the oxygen sensor is provided with multiple layers of the substrate. For example, two or three substrate layers may be provided. Those skilled in the art can decide according to the actual situation, and no specific limitation is made here.

[0054] In this example, the oxygen sensor also includes a heater. The oxygen sensor comprises three stacked substrates, with the heater disposed between the first and second substrates, and the heater electrically connected to both the first and third substrates.

[0055] In this example, the heater has a first insulating layer at each end facing the first substrate and the second substrate. The first insulating layer at each opposite end of the heater is suitable for insulating it from the first substrate and the second substrate.

[0056] In this example, the oxygen sensor also includes a reference electrode mounted within the second substrate and electrically connected to both the first and third substrates. The reference electrode provides a stable reference potential within the oxygen sensor, ensuring its accuracy and stability. This stable reference potential enables the oxygen sensor to accurately measure and report the oxygen concentration in the exhaust gas.

[0057] In this example, a second insulating layer is disposed on the exterior of the first substrate, and the second insulating layer avoids the electrodes on the first substrate. The second insulating layer on the exterior of the first substrate is suitable for insulation from external components, and the second insulating layer can avoid the electrodes on the first substrate.

[0058] In one example, the oxygen sensor is stacked with two substrates: a heating layer substrate and a detection layer substrate. The oxygen sensor may also have two substrates, one for heating and one for detection. The heater is disposed in the heating layer substrate, and the detection layer substrate includes an oxide layer with a pair of electrodes on both sides and an internal reference gas cavity.

[0059] In this example, the first and second insulating layers are formed by printing, drying, and sintering a paste with alumina as the substrate. The surface of the insulating layer is printed with corresponding heating electrodes, reference electrodes, and external electrodes, which are formed by printing, drying, and sintering a paste with platinum powder as the main powder.

[0060] According to another embodiment of this application, a method for preparing a substrate for the oxygen sensor of the above embodiment is provided, the method comprising:

[0061] The raw materials are ball-milled with organic additives.

[0062] Add a binder and continue ball milling to obtain a slurry;

[0063] The slurry is cast into a blank;

[0064] Electrodes are screen-printed onto the blank to prepare a green blank;

[0065] The green body is sintered to prepare the substrate;

[0066] The raw materials include zirconium oxide powder, niobium pentoxide powder, trivalent oxide powder, and alumina powder;

[0067] The trivalent oxide includes one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide, and neodymium oxide.

[0068] like Figure 1 As shown, the method for fabricating the substrate of the oxygen sensor in the above embodiment includes:

[0069] S1. Ball milling with organic additives. The raw materials are added to a ball mill jar according to a specified ratio, along with organic additives, to ensure thorough mixing of the various powders in the raw materials. This also helps reduce particle size, resulting in finer powders. Organic additives include dispersants and / or defoamers, which not only disperse the slurry and promote uniform mixing of various powders but also aid in powder shaping. The raw materials are ball milled with organic additives for 12 to 24 hours. For example, milling for 15, 18, or 22 hours is possible, depending on the specific circumstances, and is not specifically limited here.

[0070] In this example, the raw materials include zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, and alumina powder. During ball milling, the ball mill jar or sand mill uses an oxygen sensor liner and zirconium oxide grinding balls to prevent the introduction of impurities.

[0071] S2. Add binder and continue ball milling to obtain a slurry. After ball milling the raw materials with organic additives for a preset time, add binder and continue ball milling to obtain a slurry. Adding a certain proportion of binder can improve the adhesion of the powder, etc. For example, the content of the binder is 5wt%-15wt% of the total amount of the raw materials. For example, the content of the binder can be 6wt%, 6.65wt%, 8wt%, 11wt%, 13.5wt%, or 14wt%, etc., which can be determined by those skilled in the art according to the actual situation, and is not specifically limited here.

[0072] The process involves adding a binder and then ball milling for 4 to 8 hours to obtain a slurry. For example, ball milling can be done for 5 or 6 hours, depending on the specific circumstances, and no specific limitation is made here.

[0073] In this example, the adhesive comprises polyvinyl butyral and a plasticizer, wherein the mass ratio of polyvinyl butyral to plasticizer is 1:1-2. For example, the mass ratio of polyvinyl butyral to plasticizer can be 1:1, 1:1.5, or 1:2, etc. The plasticizer can be dioctyl phthalate (DOP), etc.

[0074] S3. Cast the slurry into a green body. The slurry, which has been ball-milled, is cast into a green body using a casting process. The casting temperature range includes 30℃, 45℃, 55℃, 75℃, and 85℃. By sequentially passing the slurry through multiple gradually increasing temperature ranges, the problem of excessively high temperature at once, which would cause the surface to dry too quickly while the interior remains undried, is avoided.

[0075] Of course, the setting of the drying temperature zone in the casting process can be determined by those skilled in the art according to the actual situation, and no specific limitation is made here.

[0076] S4. Screen-print electrodes onto the blank to prepare a green blank. After vacuuming the discharged material, it is cast into a 0.15mm-0.25mm thick film using a steel strip casting machine. The film can be cut and then screen-printed sequentially with an insulating layer, an electrode layer, and a diffusion barrier. The green blank is then dried and isostatically pressed.

[0077] S5. Sinter the green body to prepare the substrate. The green body sintering includes: raising the temperature from room temperature to 600°C for 400 min and holding for 2 h, raising the temperature from 600°C to 1150°C for 300 min and holding for 2 h, raising the temperature from 1150°C to 1300°C for 150 min and holding for 2 h, raising the temperature from 1300°C to 1500°C for 50 min and holding for 1 h-2 h, then lowering the temperature to 900°C for 150 min, and finally naturally cooling to room temperature.

[0078] The sintering atmosphere can be air; no pressurization is required. The resulting ceramic undergoes further processing, including surface grinding and polishing, followed by laser cutting into the final product. For example, an oxygen sensor core with dimensions of approximately 55mm x 4.1mm x 1.1mm (length x width x height) can be manufactured.

[0079] In one example, the trivalent oxide is yttrium oxide, and the yttrium oxide powder accounts for X% of the total raw material, satisfying: 7.5wt% ≤ X ≤ 8.5wt%. The niobium pentoxide powder accounts for M% of the total zirconium oxide powder and yttrium oxide powder, satisfying: 7wt% ≤ X - 0.85M ≤ 8wt%. Here, 0.85 is the molecular weight ratio of yttrium oxide to niobium pentoxide. That is, if yttrium oxide is replaced with other trivalent oxides, 0.85 is replaced by the molecular weight ratio of the corresponding trivalent oxide to niobium pentoxide.

[0080] In this example, the median particle size of yttrium oxide can be 0.5 μm–1 μm. The median particle size of zirconium oxide is 1 μm–3 μm, with a specific surface area of ​​5 μm. 2 / g-7m 2 / g. The percentage (X) of yttrium oxide powder in the total amount of zirconium oxide powder and yttrium oxide powder satisfies: 7.5wt% ≤ X ≤ 8.5wt%. For example, the content of yttrium oxide powder can be 7.6wt%, 7.8wt%, or 8.3wt%, etc., which can be determined by those skilled in the art according to the actual situation, and is not specifically limited here. The addition of yttrium oxide to the zirconium oxide powder can stabilize the zirconium oxide.

[0081] The proportion (M) of the niobium pentoxide powder in the total amount of zirconium oxide and yttrium oxide satisfies: 7wt% ≤ X - 0.85M ≤ 8wt%, where 0.85 is the molecular weight ratio of yttrium oxide and niobium pentoxide. This limitation is beneficial for improving the performance of the substrate, providing both high impact resistance and toughness. X and M can further satisfy: 7.3wt% ≤ X - 0.85M ≤ 7.7wt%, for example, X - 0.85M can be 7.4wt%, 7.5wt%, or 7.6wt%, etc. The median particle size of the niobium pentoxide powder is 0.5μm-1μm.

[0082] In one example, the raw material also includes alumina powder, wherein the alumina accounts for Z of the total raw material, satisfying: 1 ≤ M: Z ≤ 3. The defined niobium and aluminum content relationship in the oxygen sensor is beneficial for improving the substrate performance, providing both high impact resistance and toughness. For example, M: Z can be 1.2, 1.5, 2, 2.5, or 2.8, etc. Those skilled in the art can determine this according to the actual situation, and no specific limitation is made here.

[0083] The relationship between M and Z can be further satisfied that 1.5 ≤ M : Z ≤ 2.5.

[0084] In this example, the oxygen sensor can be used to detect the oxygen concentration in the exhaust gas of a vehicle engine and send a feedback signal to the electronic control unit (ECU). The ECU then controls the amount of fuel injected by the injectors to maintain the air-fuel ratio of the mixture near the theoretical value. The substrate of the oxygen sensor in this application has good conductivity and improved properties such as hardness, toughness, and average bending strength, as well as an increased average number of on / off aging cycles.

[0085] The present invention will be described in detail below through examples, wherein the trivalent oxide powder is yttrium oxide powder. In the following examples and comparative examples,

[0086] Fracture toughness Kic: Hardness tester indentation method. For example, using a diamond indenter, a pressure of 10 kg, and a test time of 15 s.

[0087] Hardness Hv: Hardness tester and indentation method. For example, using a diamond indenter, a pressure of 10 kg, and a test time of 15 s.

[0088] Bending strength: Using a universal testing machine, the sample to be tested is placed on a three-point bending clamp with a width of 32mm and a pressing speed of 2mm / min.

[0089] On / off aging: Using an aging test bench, the test conditions are set to 12V voltage, with one minute of power-on and one minute of power-off as one cycle, and the final number of cycles is recorded.

[0090] Assembly yield: The probability of inserting the prepared oxygen sensor core into the metal component without damage is recorded.

[0091] The experimental data for each embodiment and comparative example are shown in Table 1.

[0092] Example 1

[0093] Raw materials: The total raw material mass is 200g. Weigh 91.12wt% zirconium oxide (ZrO2), 8wt% yttrium oxide (Y2O3), 0.59wt% niobium pentoxide (Nb2O5), and 0.29wt% aluminum oxide (Al2O3) according to the proportion.

[0094] S1. Add organic additives to the raw materials and ball mill them;

[0095] The above-mentioned powders were ball-milled in a ball mill jar with organic additives for 12 hours.

[0096] S2. Add binder and continue ball milling to obtain slurry;

[0097] Then, add 5.65 wt% each of polyvinyl butyral and DOP to the ball mill jar and continue ball milling for 5 hours to obtain a slurry.

[0098] S3. Cast the slurry into a blank;

[0099] After ball milling, the slurry is fed into a steel strip casting machine under vacuum to produce a 0.15mm thick blank. The casting process involves temperature zones of 30℃, 45℃, 55℃, 75℃, and 85℃. Drying the slurry sequentially through these gradually increasing temperature zones avoids the problem of excessively high temperatures at once, which could cause the surface to dry too quickly while the interior remains undried.

[0100] S4. Screen print electrodes onto the blank to prepare a green blank;

[0101] The blanks are stacked to thicknesses of 0.6 mm, 0.45 mm, and 0.3 mm, respectively, to serve as the heating layer, intermediate layer, and functional layer. Then, insulating alumina layers and platinum electrode layers of different thicknesses are screen-printed on different layers in sequence. After drying, the different layers are stacked and statically pressed to form a green blank.

[0102] S5. Sinter the green blank to prepare the substrate;

[0103] The green blank was placed in an air sintering furnace, heated from room temperature to 600℃ over 400 minutes and held for 2 hours, then heated from 600℃ to 1150℃ over 300 minutes and held for 2 hours, then heated from 1150℃ to 1470℃ over 150 minutes and held for 2 hours, then cooled to 900℃ over 150 minutes, and finally allowed to cool naturally to room temperature. The sintered product was then polished and laser-cut to produce the final sample, with dimensions of 55mm*4.1mm*1.1mm (length*width*height). The sides were flat-ground and polished before testing.

[0104] The prepared sample was subjected to high-energy XRF detection, and its constituent elements were: Zr 67.5 wt%, Y 6.4 wt%, Nb 0.5 wt%, and Al 0.2 wt%.

[0105] XRD analysis revealed the phase composition, specifically, the phase types were determined using an X-ray diffractometer, including: 98 wt% tetragonal zirconia and 2 wt% monoclinic zirconia.

[0106] Example 2

[0107] Raw materials: The total raw material mass is 200g. Weigh 89.73wt% zirconium oxide (ZrO2), 8.5wt% yttrium oxide (Y2O3), 1.18wt% niobium pentoxide (Nb2O5), and 0.59wt% aluminum oxide (Al2O3) in proportion.

[0108] S1. Add organic additives to the raw materials and ball mill them;

[0109] Several powders were ball-milled for 12 hours with organic additives in a ball mill jar.

[0110] S2. Add binder and continue ball milling to obtain slurry;

[0111] Then, add 5.65 wt% each of polyvinyl butyral and DOP to the ball mill jar and continue ball milling for 5 hours to obtain a slurry.

[0112] S3. Cast the slurry into a blank;

[0113] After ball milling, the slurry is fed into a steel strip casting machine under vacuum to produce a 0.15mm thick blank. The casting process involves temperature zones of 30℃, 45℃, 55℃, 75℃, and 85℃. Drying the slurry sequentially through these gradually increasing temperature zones avoids the problem of excessively high temperatures at once, which could cause the surface to dry too quickly while the interior remains undried.

[0114] S4. Screen print electrodes onto the blank to prepare a green blank;

[0115] The blanks are stacked to thicknesses of 0.6 mm, 0.45 mm, and 0.3 mm, respectively, to serve as the heating layer, intermediate layer, and functional layer. Then, insulating alumina layers and platinum electrode layers of different thicknesses are screen-printed on different layers in sequence. After drying, the different layers are stacked and statically pressed to form a green blank.

[0116] S5. Sinter the green blank to prepare the substrate;

[0117] The green blank was placed in an air sintering furnace, heated from room temperature to 600℃ over 400 minutes and held for 2 hours, then heated from 600℃ to 1150℃ over 300 minutes and held for 2 hours, then heated from 1150℃ to 1470℃ over 150 minutes and held for 2 hours, then cooled to 900℃ over 150 minutes, and finally allowed to cool naturally to room temperature. The sintered product was then polished and laser-cut to produce the final sample, with dimensions of 55mm*4.1mm*1.1mm (length*width*height). The sides were flat-ground and polished before testing.

[0118] The prepared sample was subjected to high-energy XRF detection, and the constituent elements were: Zr 66.5 wt%, Y 6.7 wt%, Nb 0.9 wt%, and Al 0.4 wt%.

[0119] The phases detected by XRD included: 97.5 wt% tetragonal zirconia and 2.5 wt% monoclinic zirconia.

[0120] Example 3

[0121] Raw materials: The total raw material mass is 200g. Weigh 91.645wt% zirconium oxide (ZrO2), 8wt% yttrium oxide (Y2O3), 0.235wt% niobium pentoxide (Nb2O5), and 0.12wt% aluminum oxide (Al2O3) in proportion.

[0122] S1. Add organic additives to the raw materials and ball mill them;

[0123] The above-mentioned powders were ball-milled in a ball mill jar with organic additives for 12 hours.

[0124] S2. Add binder and continue ball milling to obtain slurry;

[0125] Then, add 5.65 wt% each of polyvinyl butyral and DOP to the ball mill jar and continue ball milling for 5 hours to obtain a slurry.

[0126] S3. Cast the slurry into a blank;

[0127] After ball milling, the slurry is fed into a steel strip casting machine under vacuum to produce a 0.15mm thick blank. The casting process involves temperature zones of 30℃, 45℃, 55℃, 75℃, and 85℃. Drying the slurry sequentially through these gradually increasing temperature zones avoids the problem of excessively high temperatures at once, which could cause the surface to dry too quickly while the interior remains undried.

[0128] S4. Screen print electrodes onto the blank to prepare a green blank;

[0129] The blanks are stacked to thicknesses of 0.6 mm, 0.45 mm, and 0.3 mm, respectively, to serve as the heating layer, intermediate layer, and functional layer. Then, insulating alumina layers and platinum electrode layers of different thicknesses are screen-printed on different layers in sequence. After drying, the different layers are stacked and statically pressed to form a green blank.

[0130] S5. Sinter the green blank to prepare the substrate;

[0131] The green blank was placed in an air sintering furnace, heated from room temperature to 600℃ over 400 minutes and held for 2 hours, then heated from 600℃ to 1150℃ over 300 minutes and held for 2 hours, then heated from 1150℃ to 1470℃ over 150 minutes and held for 2 hours, then cooled to 900℃ over 150 minutes, and finally allowed to cool naturally to room temperature. The sintered product was then polished and laser-cut to produce the final sample, with dimensions of 55mm*4.1mm*1.1mm (length*width*height). The sides were flat-ground and polished before testing.

[0132] The prepared sample was subjected to high-energy XRF detection, and the constituent elements were: Zr 67.9 wt%, Y 6.3 wt%, Nb 0.1 wt%, and Al 0.1 wt%.

[0133] The phases detected by XRD included: 98.5 wt% tetragonal zirconia and 1.5 wt% monoclinic zirconia.

[0134] Comparative Example 1

[0135] Raw materials: The total raw material mass is 200g. Weigh 91.71wt% zirconium oxide (ZrO2), 8wt% yttrium oxide (Y2O3), and 0.29wt% aluminum oxide (Al2O3) in proportion.

[0136] S1. Add organic additives to the raw materials and ball mill them;

[0137] The above-mentioned powders were ball-milled in a ball mill jar with organic additives for 12 hours.

[0138] S2. Add binder and continue ball milling to obtain slurry;

[0139] Then, add 6.65 wt% each of polyvinyl butyral and DOP to the ball mill jar and continue ball milling for 6 hours to obtain a slurry.

[0140] S3. Cast the slurry into a blank;

[0141] After ball milling, the slurry is fed into a steel strip casting machine under vacuum to produce a 0.15mm thick blank. The casting process involves temperature zones of 30℃, 45℃, 55℃, 75℃, and 85℃. Drying the slurry sequentially through these gradually increasing temperature zones avoids the problem of excessively high temperatures at once, which could cause the surface to dry too quickly while the interior remains undried.

[0142] S4. Screen print electrodes onto the blank to prepare a green blank;

[0143] The blanks are stacked to thicknesses of 0.6 mm, 0.45 mm, and 0.3 mm, respectively, to serve as the heating layer, intermediate layer, and functional layer. Then, insulating alumina layers and platinum electrode layers of different thicknesses are screen-printed on different layers in sequence. After drying, the different layers are stacked and statically pressed to form a green blank.

[0144] S5. Sinter the green blank to prepare the substrate;

[0145] The green blank was placed in an air sintering furnace, heated from room temperature to 600℃ over 400 minutes and held for 2 hours, then heated from 600℃ to 1150℃ over 300 minutes and held for 2 hours, then heated from 1150℃ to 1470℃ over 150 minutes and held for 2 hours, then cooled to 900℃ over 150 minutes, and finally allowed to cool naturally to room temperature. The sintered product was then polished and laser-cut to produce the final sample, with dimensions of 55mm*4.1mm*1.1mm (length*width*height). The sides were flat-ground and polished before testing.

[0146] The prepared sample was subjected to high-energy XRF detection, and the constituent elements were: Zr 67.5 wt%, Y 6.5 wt%, and Al 0.3 wt%.

[0147] The phases detected by XRD included: 99.6 wt% tetragonal zirconia and 0.4 wt% monoclinic zirconia.

[0148] The phases detected by XRD included: 98 wt% tetragonal zirconia and 2 wt% monoclinic zirconia.

[0149] Table 1. Mechanical properties of oxygen sensors in the embodiments and comparative examples.

[0150]

[0151] Examples 1 to 3 present data on substrates prepared by weighing zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, and alumina powder in a specific ratio. Comparative Example 1 presents data on substrates prepared by weighing zirconium oxide powder, yttrium oxide powder, and alumina powder in a specific ratio.

[0152] As shown in Table 1, based on the data from Examples 1 to 3, the oxygen sensor substrate prepared according to the proportions of Zr, Y, Nb, and Al in the substrate of the oxygen sensor of this application exhibits high toughness and average bending strength, a large number of on / off aging cycles, and a high assembly yield, meeting the expected requirements. Furthermore, compared to the comparative example, the hardness of the substrate is also similar, meeting the expected requirements. Comparing the data from Examples 1 to 3 with Comparative Example 1, it can be seen that the oxygen sensor of this application, by adding niobium pentoxide and preparing zirconium oxide, yttrium oxide, niobium pentoxide, and aluminum oxide in a certain proportion, enables the oxygen sensor substrate to have high toughness and average bending strength, and significantly improves the number of on / off aging cycles and the assembly yield. Specifically, niobium pentoxide can enhance the activity of tetragonal zirconium oxide by weakening the effect of yttrium oxide, thereby improving toughness.

[0153] The above embodiments mainly describe the differences between the various embodiments. As long as the different optimization features between the various embodiments are not contradictory, they can be combined to form a better embodiment. For the sake of brevity, they will not be elaborated here.

[0154] While specific embodiments of the invention have been described in detail by way of examples, those skilled in the art should understand that the examples are for illustrative purposes only and not intended to limit the scope of the invention. Those skilled in the art should understand that modifications can be made to the above embodiments without departing from the scope and spirit of the invention. The scope of the invention is defined by the appended claims.

Claims

1. An oxygen sensor, characterized in that, include: A substrate, the substrate comprising a zirconium oxide layer; The zirconium oxide layer contains, in terms of elements, Zr, trivalent elements, Nb, and Al; as well as, The zirconium oxide layer comprises 96 wt% to 99.7 wt% tetragonal zirconium oxide, with the remaining phase being monoclinic zirconium oxide. In the tetragonal zirconium oxide, the molar content of trivalent element oxides to the total molar content of zirconium oxide, trivalent element oxides, and niobium oxide is a, satisfying a = 4.5 mol% to 5.5 mol%, and the molar content of niobium oxide to the total molar content of zirconium oxide, trivalent element oxides, and niobium oxide is b, satisfying ab = 4 mol% to 5 mol%. The trivalent elements include one or more of Y, Sm, Er, Sc, and Nd.

2. The oxygen sensor according to claim 1, characterized in that, a and b satisfy the condition that ab = 4.3 mol% to 4.8 mol%.

3. The oxygen sensor according to claim 1, characterized in that, The trivalent element is Y, and the zirconium oxide layer contains, by elemental composition: 65.12 wt% to 67.91 wt% Zr, 5.91 wt% to 6.71 wt% Y, 0.05 wt% to 1.21 wt% Nb, and 0.1 wt% to 0.93 wt% Al.

4. The oxygen sensor according to claim 3, characterized in that, The zirconium oxide layer contains, in terms of elements, 65.65 wt% to 67.12 wt% of Zr, 5.91 wt% to 6.71 wt% of Y, 0.06 wt% to 0.97 wt% of Nb, and 0.041 wt% to 0.75 wt% of Al.

5. The oxygen sensor according to claim 1, characterized in that, The zirconium oxide layer comprises 97 wt% to 99 wt% tetragonal zirconium oxide, with the remainder being monoclinic zirconium oxide.

6. The oxygen sensor according to claim 1, characterized in that, The oxygen sensor is provided with multiple layers of the substrate.

7. The oxygen sensor according to claim 6, characterized in that, It also includes a heater. The oxygen sensor is stacked with three substrates. The heater is disposed between the first substrate and the second substrate, and the heater is electrically connected to the first substrate and the third substrate, respectively.

8. The oxygen sensor according to claim 7, characterized in that, The heater has a first insulating layer at each end facing the first substrate and the second substrate.

9. The oxygen sensor according to claim 7, characterized in that, It also includes a reference electrode, which is mounted in the second substrate and electrically connected to the first substrate and the third substrate, respectively.

10. The oxygen sensor according to claim 7, characterized in that, The first substrate has a second insulating layer on its exterior, and the second insulating layer avoids the electrodes on the first substrate.

11. The oxygen sensor according to claim 6, characterized in that, The oxygen sensor is provided with two substrates stacked together, namely a heating layer substrate and a detection layer substrate.

12. The oxygen sensor according to claim 1, characterized in that, The substrate has a hardness greater than or equal to 1200 Hv and a toughness greater than or equal to 6 MPa. 0.5 The substrate has a bending strength greater than or equal to 700 MPa, a switching aging cycle greater than or equal to 8000, and an assembly yield greater than or equal to 80%.

13. A method for preparing a substrate for an oxygen sensor as described in any one of claims 1 to 12, characterized in that, include: The raw materials are ball-milled with organic additives. Add a binder and continue ball milling to obtain a slurry; The slurry is cast into a blank; Electrodes are screen-printed onto the blank to prepare a green blank; The green body is sintered to prepare the substrate; The raw materials include zirconium oxide powder, niobium pentoxide powder, trivalent oxide powder, and alumina powder; Among them, trivalent oxides include one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide, and neodymium oxide.

14. The method according to claim 13, characterized in that, The trivalent oxide is yttrium oxide, and the yttrium oxide powder accounts for X of the total amount of the raw materials, satisfying: 7.5wt% ≤ X ≤ 8.5wt%. The niobium pentoxide powder accounts for M of the total amount of the zirconium oxide powder and yttrium oxide powder, satisfying: 7wt% ≤ X - 0.85M ≤ 8wt%.

15. The method according to claim 14, characterized in that, The X and M satisfy the condition that 7.3wt% ≤ X - 0.85M ≤ 7.7wt%.

16. The method according to claim 13, characterized in that, The proportion of alumina powder to the total amount of raw materials, Z, satisfies: 1≤M:Z≤3.

17. The method according to claim 16, characterized in that, 1.5≤M:Z≤2.5.

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