Oxygen sensor and preparation method for oxygen sensor substrate

Abstract

An oxygen sensor and a preparation method for an oxygen sensor substrate. The oxygen sensor comprises a substrate, the substrate having a zirconia layer, and the zirconia layer comprising, in terms of elements: Zr, a trivalent element, Nb, and Al. The phases of the zirconia layer comprise 96 wt％-99.7 wt％ of tetragonal zirconia, the remainder is monoclinic zirconia. In the tetragonal zirconia, the ratio of the molar content of a trivalent element oxide to the total molar content of the zirconia, the trivalent element oxide, and niobium oxide is a, satisfying a＝4.5 mol％-5.5 mol％. The ratio of the molar content of the niobium oxide to the total molar content of the zirconia, the trivalent element oxide, and the niobium oxide is b, satisfying a-b＝4 mol％-5 mol％, and the trivalent element comprising one or more of Y, Sm, Er, Sc and Nd.

Description

Oxygen sensor and method for manufacturing oxygen sensor substrate

[0001] This application claims priority to Chinese Patent Application No. 202410756218.3, 202410756893.6 and 202410757653.8, filed on June 12, 2024, with the Chinese Patent Office, the contents of which are incorporated herein by reference in their entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of oxygen sensors, and more particularly, to an oxygen sensor and a method for manufacturing an oxygen sensor substrate. BACKGROUND

[0003] In the related art, an oxygen sensor generally utilizes the difference in oxygen concentration between the inner and outer sides of a substrate to generate a potential difference, thereby achieving the purpose of detecting the oxygen concentration. The substrate of the oxygen sensor is generally prepared by flow casting zirconia powder stabilized by a stabilizer, and the mechanical properties of the current substrate are poor.

[0004] Therefore, there is a need to provide a new technical solution to solve the above technical problems. TECHNICAL SOLUTION

[0005] An object of the present application is to provide a new technical solution for an oxygen sensor.

[0006] In one aspect, the present application provides an oxygen sensor. The oxygen sensor includes a substrate,

[0007] The substrate includes a zirconia layer;

[0008] The zirconia layer contains, in terms of elements, Zr, a trivalent element, Nb, and Al; and

[0009] The phase of the zirconia layer contains 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%.

[0010] The trivalent element includes one or more of Y, Sm, Er, Sc, and Nd.

[0011] The present application also provides a method for manufacturing the substrate of the above-mentioned oxygen sensor, comprising:

[0012] The raw materials are ball milled with an organic additive;

[0013] adding a binder and continuing ball milling to obtain a slurry;

[0014] casting the slurry into a green body;

[0015] screen printing electrodes on the green body to prepare a green body;

[0016] sintering the green body to prepare the substrate;

[0017] The raw material comprises zirconium oxide powder, niobium pentoxide powder, trivalent oxide powder and aluminum oxide powder.

[0018] The trivalent oxide comprises one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide and neodymium oxide.

[0019] The application further provides another oxygen sensor, comprising:

[0020] a substrate having a zirconium oxide layer;

[0021] The zirconium oxide layer contains, in terms of elements, 59.9wt%-67.5wt% Zr, 5.23wt%-6.6wt% Y, 0.05wt%-1.21wt% Nb, 0.44wt%-3.57wt% Ba, 0-0.46wt% Si and 0.18wt%-2.77wt% Al; and

[0022] The phase of the zirconium oxide layer contains 88.5wt%-98.5wt% tetragonal zirconium oxide, 0.83wt%-6.7wt% barium aluminate, 0-3.55wt% mullite phase, and the remaining phase is monoclinic zirconium oxide.

[0023] The application further provides a preparation method of the substrate of the above oxygen sensor, comprising:

[0024] adding a raw material to an organic auxiliary agent for ball milling;

[0025] adding a binder and continuing ball milling to obtain a slurry;

[0026] casting the slurry into a green body;

[0027] screen printing electrodes on the green body to prepare a green body;

[0028] sintering the green body to prepare the substrate;

[0029] The raw material includes zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder and barium oxide powder, the yttrium oxide powder accounts for X2 of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies 7.5wt%≤X2≤8.5wt%, the niobium pentoxide powder accounts for M2 of the total amount of the zirconium oxide and yttrium oxide, and satisfies 7wt%≤X2-0.85M2≤8wt%, and the barium oxide powder accounts for A2 of the total amount of the raw material, and satisfies 0.5wt%≤A2≤4wt%.

[0030] The application also provides another oxygen sensor.

[0031] The substrate has a zirconium oxide layer.

[0032] The zirconium oxide layer contains, in terms of elements:

[0033] Zr, Y, Nb, Si, Al; and

[0034] The phase of the zirconium oxide layer contains tetragonal zirconium oxide, mullite phase, aluminum oxide phase and monoclinic zirconium oxide.

[0035] The application also provides a method for preparing the substrate of the above oxygen sensor, and the method comprises:

[0036] The raw material is ball milled with an organic additive;

[0037] A binder is added to continue ball milling to obtain a slurry;

[0038] The slurry is cast into a green body;

[0039] An electrode is screen printed on the green body to prepare a green body;

[0040] The green body is sintered to prepare the substrate.

[0041] The raw material includes zirconium oxide powder, yttrium oxide powder and niobium pentoxide powder, the yttrium oxide powder accounts for X3 of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies 7.5wt%≤X3≤8.5wt%, and the niobium pentoxide powder accounts for M3 of the total amount of the zirconium oxide and yttrium oxide, and satisfies 7wt%≤X3-0.85M3≤8wt%.

[0042] One technical effect of the application is that the oxygen sensor provided by the application includes a substrate with good mechanical properties.

[0043] Other features and advantages of the application will become apparent from the following detailed description of exemplary embodiments thereof, with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0044] 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.

[0045] Figure 1 is a flow chart of a method for preparing a substrate of an oxygen sensor according to the present application. Embodiments of the present application

[0046] Various exemplary embodiments of the present application will now be described in detail with reference to the figures. It should be noted that the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments are not limiting to the scope of the present application unless otherwise specifically stated.

[0047] The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the scope of the application its application or uses.

[0048] Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail herein, but should be considered as part of the specification, where appropriate.

[0049] In all of the examples shown and discussed herein, any specific values should be interpreted as merely exemplary, and not as a limitation. Thus, other examples of exemplary embodiments can have different values.

[0050] It should be noted that like reference numerals and letters in the various figures indicate similar items, and thus, once an item is defined in one figure, it need not be discussed further in subsequent figures.

[0051] According to one embodiment of the present application, an oxygen sensor is provided. The oxygen sensor comprises a substrate, the substrate having a first zirconia layer. The first zirconia layer comprises, in terms of elements: Zr, a trivalent element, Nb, and Al; and a phase of the first zirconia layer comprises: 96wt% to 99.7wt% of tetragonal zirconia, and the rest of the phase is monoclinic zirconia, in the tetragonal zirconia, a ratio of a molar content of the trivalent element oxide to a total molar content of the zirconia, the trivalent element oxide, and the niobium oxide is a, which satisfies a = 4.5mol% to 5.5mol%, a ratio of a molar content of the niobium oxide to the total molar content of the zirconia, the trivalent element oxide, and the niobium oxide is b, which satisfies a - b = 4mol% to 5mol%; wherein the trivalent element comprises one or more of Y (yttrium), Sm (samarium), Er (erbium), Sc (scandium), and Nd (neodymium).

[0052] In this example, the substrate of the oxygen sensor of the present application has better mechanical properties, including a significant increase in toughness and average bending strength, and a significant increase in the number of times of the substrate's on-off aging plateau, and a significant increase in the substrate's assembly yield.

[0053] For example, a can be 4.7 mol%, 4.9 mol%, 5.4 mol%, etc. Further, a and b satisfy a-b = 4.3 mol% ~ 4.8 mol%. For example, a-b can be 4.3 mol%, 4.4 mol%, 4.5 mol%, 4.6 mol%, 4.7 mol%, 4.8 mol%, etc. Those skilled in the art can determine according to the actual situation, which is not specifically limited here.

[0054] In this example, the hardness of the substrate is greater than or equal to 1200 Hv, the toughness of the substrate is greater than or equal to 6 MPam 0.5 , the bending strength of the substrate is greater than or equal to 700 Mpa, 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%.

[0055] In one example, the trivalent element is Y, and the first zirconia layer contains, in terms of elements: 65.12 wt% - 67.91 wt% Zr, 5.91 wt% - 6.71 wt% trivalent element, 0.05 wt% - 1.21 wt% Nb, and 0.1 wt% - 0.93 wt% Al.

[0056] For example, the trivalent element in the first zirconia layer is Y, and the prepared sample is subjected to high-energy XRF detection, that is, the element content of the polished sample is tested using an energy dispersive X-ray fluorescence spectrometer EDX-7000. Among them, Zr is 67.5 wt%, Y is 6.4 wt%, Nb is 0.5 wt%, and Al is 0.2 wt%.

[0057] The prepared sample is subjected to XRD detection to determine the phase, that is, the phase type is tested using an X-ray diffractometer, including: 98 wt% of tetragonal zirconia, and 2 wt% of monoclinic zirconia.

[0058] Of course, the specific content of each element in the first zirconia layer can be determined by those skilled in the art according to the actual situation, which is not specifically limited here.

[0059] In one example, the first zirconia layer contains, in terms of elements: 65.65 wt% - 67.12 wt% Zr, 5.91 wt% - 6.71 wt% trivalent element, 0.06 wt% - 0.97 wt% Nb, and 0.041 wt% - 0.75 wt% Al.

[0060] In this example, the above element ratio can further improve the hardness, toughness and average bending strength of the oxygen sensor, and the average on-off aging frequency of the prepared substrate is also greater.

[0061] In one example, the phase of the zirconium oxide layer comprises 97wt%-99wt% of tetragonal zirconium oxide and the rest is monoclinic zirconium oxide.

[0062] In this example, the above phase ratio can further improve the hardness, toughness and average bending strength of the oxygen sensor, and the average number of on-off aging of the manufactured substrate is also greater.

[0063] In this example, the oxygen sensor can also contain other phases, but it has no negative effect on the oxygen sensor of the present application. In the present application, the above phase content contained in the oxygen sensor is based on the oxygen sensor. The elemental composition of the oxygen sensor can also contain other elements, such as oxygen elements, etc.

[0064] In one example, the oxygen sensor is stacked with multiple layers of substrates. For example, two or three layers of substrates can be provided. Those skilled in the art can determine according to the actual situation, which is not limited here.

[0065] In this example, the oxygen sensor also includes a heater. The oxygen sensor includes three layers of stacked substrates, and the 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.

[0066] In this example, the heater is provided with a first insulating layer at both ends facing the first substrate and the second substrate. The opposite ends of the heater are provided with a first insulating layer, which is suitable for insulation with the first substrate and the second substrate.

[0067] In this example, the oxygen sensor also includes a reference electrode, which is installed in the second substrate and is electrically connected to the first substrate and the third substrate, respectively. The reference electrode provides a stable reference potential in the oxygen sensor, ensuring the accuracy and stability of the sensor. This stable reference potential enables the oxygen sensor to accurately measure and feedback the oxygen concentration in the exhaust gas.

[0068] In this example, the first substrate is provided with a second insulating layer on the outside, and the second insulating layer avoids the electrodes on the first substrate. The first substrate is provided with a second insulating layer on the outside, which is suitable for insulation with external parts, and the second insulating layer can avoid the electrodes on the first substrate.

[0069] In one example, the oxygen sensor is stacked with two layers of substrates, which are heating layer substrate and detection layer substrate, respectively. The oxygen sensor can also be provided with two layers of substrates, which are heating layer substrate and detection layer substrate, respectively. The heater is arranged in the heating layer substrate, and the detection layer substrate includes an oxidation layer with a pair of electrodes on both sides and an internal reference gas cavity.

[0070] In this example, the first and second insulating layers are alumina-based slurry printed, dried, sintered. The insulating layer surface is printed with corresponding electrode layers such as heating electrode, reference electrode and outer electrode, etc. The electrodes are all platinum powder-based slurry printed, dried and sintered.

[0071] According to another embodiment of the present application, a method for preparing the substrate of the oxygen sensor of the above-mentioned embodiments is provided, the method comprising:

[0072] adding raw materials to an organic aid for ball milling;

[0073] adding a binder for continuous ball milling to obtain a slurry;

[0074] flowing the slurry into a green body;

[0075] screen printing electrodes on the green body to prepare a green body;

[0076] sintering the green body to prepare a substrate;

[0077] wherein the raw materials include zirconia powder, niobium pentoxide powder, trivalent oxide powder and alumina powder;

[0078] wherein the trivalent oxide includes one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide and neodymium oxide.

[0079] As shown in FIG. 1, the method for preparing the substrate of the oxygen sensor of the above-mentioned embodiments comprises:

[0080] S11, adding raw materials to an organic aid for ball milling. The raw materials are added to the ball mill tank in proportion, and an organic aid is added for ball milling, so that the various powders in the raw materials are fully mixed, and the particle size is also reduced, thereby obtaining finer powders. The organic aid includes dispersants and / or defoamers, etc. The organic aid can not only disperse the slurry and promote the mixing of various powders, but also help the powder forming. The raw materials are ball milled for 12 to 24 hours with the organic aid. For example, the ball milling time can be 15 hours, 18 hours or 22 hours, etc. The skilled person in the art can determine the ball milling time according to the actual situation, which is not limited here.

[0081] In this example, the raw materials include zirconia powder, yttrium oxide powder, niobium pentoxide powder and alumina powder. When ball milling, the ball mill tank or sand mill uses the inner lining of the oxygen sensor and zirconia grinding balls to prevent the introduction of impurities.

[0082] S12, continue ball milling after adding the binder to obtain the slurry. The raw materials are ball milled with the organic auxiliary agent for a preset time, and then the binder is added to continue ball milling to obtain the slurry. By adding a certain proportion of the binder, the adhesion of the powder can be improved, and other effects can be achieved, 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.

[0083] The binder is added and the ball milling is continued for 4-8 hours to obtain the slurry. For example, the ball milling can be continued for 5 hours or 6 hours, etc., which can be determined by those skilled in the art according to the actual situation, and is not specifically limited here.

[0084] In this example, the binder includes polyvinyl butyral and a plasticizer, and 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) or the like.

[0085] S13, the slurry is cast into a green body. The slurry obtained by ball milling is cast into a green body by a casting process. The temperature zone of the casting includes 30°C, 45°C, 55°C, 75°C, 85°C. The slurry is dried by sequentially passing through multiple temperature zones that gradually increase, which can avoid the problem that the surface dries too quickly and the inside is not dry enough due to the temperature increasing too high at one time.

[0086] 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 is not specifically limited here.

[0087] S14, silk screen electrodes on the green body to prepare a green body. The discharged material is cast into a 0.15mm-0.25mm thick film on a steel belt casting machine. The film can be cut and then the insulation layer, electrode layer and diffusion barrier are silk screened in sequence on a silk screen machine, and then the green body is dried and isostatic pressed.

[0088] S15, sintering the green body to prepare a substrate. The sintering of the green body includes: increasing from room temperature to 600°C for 400min, holding for 2h, increasing from 600°C to 1150°C for 300min, holding for 2h, increasing from 1150°C to 1300°C for 150min, holding for 2h, then increasing from 1300°C to 1500°C for 50min, holding for 1-2h, then decreasing from 1500°C to 900°C for 150min, and finally naturally cooling to room temperature.

[0089] The sintering atmosphere can be air, and no pressure is needed. The ceramic obtained after sintering can further include flat grinding and polishing, and cutting into the final product using a laser. For example, an oxygen sensor core with a length, width and height of about 55mm*4.1mm*1.1mm can be made.

[0090] In one example, the trivalent oxide is yttrium oxide, and the content of the yttrium oxide powder in the total raw material is X1, which satisfies: 7.5wt%≤X1≤8.5wt%. The content of the niobium pentoxide powder in the total zirconium oxide powder and yttrium oxide powder is M1, which satisfies: 7wt%≤X1-0.85M1≤8wt%. Wherein, 0.85 is the molecular weight ratio of yttrium oxide to niobium pentoxide. That is, if the yttrium oxide is replaced by other trivalent oxides, 0.85 is replaced by the molecular weight ratio of the corresponding trivalent oxide to niobium pentoxide.

[0091] In this example, the median particle size of the yttrium oxide can be 0.5μm-1μm. The median particle size of the zirconium oxide is 1μm-3μm, and the specific surface area is 5m 2 / g-7m 2 / g. The content of the yttrium oxide powder in the total zirconium oxide powder and yttrium oxide powder is X1, which satisfies: 7.5wt%≤X1≤8.5wt%. For example, the content of the 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. Wherein, the addition of yttrium oxide in the zirconium oxide powder can stabilize the zirconium oxide.

[0092] The content of the niobium pentoxide powder in the total zirconium oxide and yttrium oxide is M1, which satisfies: 7wt%≤X1-0.85M1≤8wt%, and 0.85 is the molecular weight ratio of yttrium oxide to niobium pentoxide. Through this limitation, it is beneficial to improve the performance of the substrate, and it has high impact resistance and toughness. Wherein, X1 and M1 can further satisfy: 7.3wt%≤X1-0.85M1≤7.7wt%, for example, X1-0.85M1 can be 7.4wt%, 7.5wt% or 7.6wt%, etc. Wherein, the median particle size of the niobium pentoxide powder is 0.5μm-1μm.

[0093] In one example, the raw material further includes an aluminum oxide powder, and the content of the aluminum oxide in the total raw material is Z1, which satisfies: 1≤M1:Z1≤3. The content relationship between niobium and aluminum in the oxygen sensor is beneficial to improve the performance of the substrate, and it has high impact resistance and toughness. For example, M1:Z1 can be 1.2, 1.5, 2, 2.5 or 2.8, etc. Those skilled in the art can determine it according to the actual situation, and it is not specifically limited here.

[0094] Wherein, the relationship between M1 and Z1 can further satisfy: 1.5≤M1:Z1≤2.5.

[0095] In this example, the oxygen sensor can be used to detect the concentration of oxygen in the exhaust gas of the vehicle engine, and send a feedback signal to the electronic control unit, which controls the amount of fuel injected by the fuel injector, so as to control the air-fuel ratio of the mixture around the theoretical value. The substrate of the oxygen sensor of the present application can have good electrical conductivity, and improve the hardness, toughness, average bending strength and other properties, and increase the average number of on-off aging.

[0096] The present application will be described in detail below by way of examples, in which the trivalent oxide powder is yttrium oxide powder. In the following examples and comparative examples,

[0097] Fracture toughness Kic: hardness tester indentation method. For example, a diamond indenter, a pressure of 10 kg, and a test pressure time of 15 s are used.

[0098] Hardness Hv: hardness tester and indentation method. For example, a diamond indenter, a pressure of 10 kg, and a test pressure time of 15 s are used.

[0099] Bending strength: using a universal testing machine, the sample to be tested is placed on a three-point bending fixture, the wide distance is set to 32 mm, and the pressing speed is 2 mm / min.

[0100] On-off aging: using an aging test bench, the test conditions are set to a voltage of 12V, 1 minute of power on and 1 minute of power off as one cycle, and the final cycle number is recorded.

[0101] Assembly yield: the prepared oxygen sensor core is inserted into the metal part, and the probability of no damage is recorded.

[0102] The test data of each example and comparative example is shown in Table 1.

[0103] Example 1-1

[0104] Raw materials: the total raw material mass is 200g, and zirconium oxide (ZrO2) 91.12wt%, yttrium oxide (Y2O3) 8wt%, niobium pentoxide (Nb2O5) 0.59wt%, and aluminum oxide (Al2O3) 0.29wt% are weighed according to the proportion.

[0105] S11, adding raw materials to organic additives for ball milling;

[0106] The above several kinds of powders are ball milled in a ball mill tank with organic additives for 12h.

[0107] S12, adding a binder for continuous ball milling to obtain a slurry;

[0108] Then 5.65wt% of polyvinyl butyral and DOP are added to the ball mill tank for continuous ball milling for 5 hours to obtain a slurry.

[0109] S13, the slurry is cast into a green body;

[0110] After ball milling, the slurry is sent into a steel belt casting machine through vacuumization to be cast to prepare a green body with a thickness of 0.15 mm. The temperature zones in the casting process include 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that are gradually increased, so that the temperature is not increased too high at one time, and the problem of too fast surface drying and internal drying is avoided.

[0111] S14, the green body is silk-screened with electrodes to prepare a green body;

[0112] The green body is stacked into a thickness of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer. Then different thicknesses of insulating alumina layers and platinum electrode layers are silk-screened on different layers, and after drying, the different layers are stacked and pressed to prepare a green body.

[0113] S15, the green body is sintered to prepare a substrate;

[0114] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400 min and kept for 2 h, increased from 600℃ to 1150℃ for 300 min and kept for 2 h, increased from 1150℃ to 1470℃ for 150 min and kept for 2 h, then decreased to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product, the final sample is prepared, and the sample has a size of 55mm*4.1mm*1.1mm and the side is polished and polished to be left for testing.

[0115] The sample prepared is detected by high-energy XRF, and the composition elements contain: Zr is 67.5wt%, Y is 6.4wt%, Nb is 0.5wt%, and Al is 0.2wt%.

[0116] XRD detects the phase, i.e., the phase type is tested by using an X-ray diffractometer, including: 98wt% of tetragonal zirconia and 2wt% of monoclinic zirconia.

[0117] Example 1-2

[0118] Raw materials: the total raw material mass is 200g, and zirconia (ZrO2) 89.73wt%, yttrium oxide (Y2O3) 8.5wt%, niobium pentoxide (Nb2O5) 1.18wt%, and aluminum oxide (Al2O3) 0.59wt% are weighed according to the proportion.

[0119] S11, the raw materials are added to the organic auxiliary agent for ball milling;

[0120] The several powders are ball milled in the ball mill tank with the organic auxiliary agent for 12h.

[0121] S12, continue ball milling by adding a binder to obtain a slurry;

[0122] Then, 5.65wt% of polyvinyl butyral and DOP were added into the ball mill tank respectively, and the ball milling was continued for 5 hours to obtain a slurry.

[0123] S13, the slurry was cast into a green body;

[0124] After the ball milling was completed, the slurry was sent into a steel belt casting machine through vacuum extraction to be cast, and a green body with a thickness of 0.15mm was prepared. The temperature zones in the casting process included 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry was dried by sequentially passing through multiple temperature zones that gradually increased, which could avoid the problem of the surface drying too quickly while the inside was not dry due to the temperature being increased too high at one time.

[0125] S14, the green body was screen printed with electrodes to prepare a green body;

[0126] The green body was stacked into a thickness of 0.6mm, 0.45mm and 0.3mm as a heating layer, an intermediate layer and a functional layer respectively. Then, different thicknesses of insulating alumina layers and platinum electrode layers were screen printed on different layers in sequence, and after drying, the different layers were stacked and pressed to prepare a green body.

[0127] S15, the green body was sintered to prepare a substrate;

[0128] The green body was placed into an air sintering furnace, and the temperature was increased from room temperature to 600℃ at a rate of 400min, and then the temperature was kept at 600℃ for 2h. The temperature was increased from 600℃ to 1150℃ at a rate of 300min, and then the temperature was kept at 1150℃ for 2h. The temperature was increased from 1150℃ to 1470℃ at a rate of 150min, and then the temperature was kept at 1470℃ for 2h. The temperature was decreased from 1470℃ to 900℃ at a rate of 150min, and then the temperature was naturally cooled to room temperature. After polishing and polishing of the sintered product, and laser cutting, the final sample was prepared, and the sample had a size of 55mm*4.1mm*1.1mm, and the side edges were polished and polished to be left for testing.

[0129] The sample prepared was detected by high-energy XRF, and the composition elements included Zr 66.5wt%, Y 6.7wt%, Nb 0.9wt%, and Al 0.4wt%.

[0130] The phase detected by XRD included tetragonal zirconia 97.5wt% and monoclinic zirconia 2.5wt%.

[0131] Examples 1-3

[0132] Raw materials: 200 g of total raw material, zirconium oxide (ZrO2) 91.645 wt%, yttrium oxide (Y2O3) 8 wt%, niobium pentoxide (Nb2O5) 0.235 wt%, and aluminum oxide (Al2O3) 0.12 wt% were weighed according to the proportion.

[0133] S11, adding raw materials to organic additives for ball milling;

[0134] The above several powders were ball milled in a ball mill tank with organic additives for 12 h.

[0135] S12, adding a binder and continuing to ball mill to obtain a slurry;

[0136] Then 5.65 wt% of polyvinyl butyral and DOP were added to the ball mill tank respectively, and the ball milling was continued for 5 hours to obtain a slurry.

[0137] S13, the slurry was cast into a green body;

[0138] After the ball milling was completed, the slurry was sent into a steel belt casting machine for casting by vacuumizing, and a green body with a thickness of 0.15 mm was prepared. The temperature zones in the casting process included 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry was dried by sequentially passing through multiple temperature zones that gradually increased, which could avoid the problem of the surface drying too fast while the inside was not dry due to the temperature increasing too high at one time.

[0139] S14, printing electrodes on the green body to prepare a green body;

[0140] The green body was stacked into a thickness of 0.6 mm, 0.45 mm, and 0.3 mm as a heating layer, an intermediate layer, and a functional layer, respectively. Then different thicknesses of insulating aluminum oxide layers and platinum electrode layers were screen printed on different layers in sequence, and after drying, the different layers were stacked and pressed to form a green body.

[0141] S15, sintering the green body to prepare a substrate;

[0142] The green body was placed into an air sintering furnace, and the temperature was increased from room temperature to 600℃ for 400 min and kept for 2 h, increased from 600℃ to 1150℃ for 300 min and kept for 2 h, increased from 1150℃ to 1470℃ for 150 min and kept for 2 h, then decreased from 1470℃ to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product, and laser cutting, the final sample was prepared, and the sample had a size of 55 mm*4.1 mm*1.1 mm and the side edges were polished and polished to be left for testing.

[0143] The sample was detected by high-energy XRF, and the composition elements contained Zr 67.9 wt%, Y 6.3 wt%, Nb 0.1 wt%, and Al 0.1 wt%.

[0144] The phases detected by XRD included: 98.5 wt% tetragonal zirconia and 1.5 wt% monoclinic zirconia.

[0145] Comparative Example 1-1

[0146] 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.

[0147] S11. Add the raw materials to the organic additives and ball mill them;

[0148] The above-mentioned powders were ball-milled in a ball mill jar with organic additives for 12 hours.

[0149] S12. Add binder and continue ball milling to obtain slurry;

[0150] 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.

[0151] S13. Cast the slurry into a green body;

[0152] 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.

[0153] S14. Screen print electrodes onto the blank to prepare a green blank;

[0154] 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.

[0155] S15. Sinter the green blank to prepare a substrate;

[0156] 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.

[0157] The prepared sample was subjected to high-energy XRF detection, and the composition elements contained: Zr was 67.5wt%, Y was 6.5wt%, and Al was 0.3wt%. The phase detected by XRD included: 99.6wt% of tetragonal zirconia and 0.4wt% of monoclinic zirconia.

[0158] The phase detected by XRD included: 98wt% of tetragonal zirconia and 2wt% of monoclinic zirconia.

[0159] Table 1 Mechanical properties of oxygen sensors of examples and comparative examples

[0160] Among them, examples 1-1 to 1-3 are the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder and aluminum oxide powder in proportion. Comparative example 1-1 is the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder and aluminum oxide powder in proportion.

[0161] From Table 1, according to the data in examples 1-1 to 1-3, the oxygen sensor substrate prepared according to the proportion of each element Zr, Y, Nb and Al in the substrate of the oxygen sensor of the present application has high toughness and average bending strength, and the on-off aging frequency is also large, and the assembly yield is high, which can meet the expected requirements. And compared with the comparative example, the hardness of the substrate is also small, which can also meet the expected requirements. By comparing the data of examples 1-1 to 1-3 with comparative example 1-1, it can be seen that by adding niobium pentoxide and preparing zirconium oxide, yttrium oxide, niobium pentoxide and aluminum oxide in a certain proportion, the substrate of the oxygen sensor can have high toughness and average bending strength, and the on-off aging frequency and assembly yield are also significantly improved. Among them, niobium pentoxide can weaken the effect of yttrium oxide to improve the activity of tetragonal zirconia to improve toughness.

[0162] The present application also provides another oxygen sensor. The oxygen sensor includes a substrate, the substrate has a second zirconium oxide layer, the second zirconium oxide layer contains, in terms of elements: 59.9wt%-67.5wt% of Zr, 5.23wt%-6.6wt% of Y, 0.05wt%-1.21wt% of Nb, 0.44wt%-3.57wt% of Ba, 0-0.46wt% of Si and 0.18wt%-2.77wt% of Al; and the phase of the zirconium oxide ceramic contains: 88.5wt%-98.5wt% of tetragonal zirconia, 0.83wt%-6.7wt% of barium aluminate, 0-3.55wt% of mullite phase, and the remaining phase is monoclinic zirconia.

[0163] In this example, the substrate of the oxygen sensor of the present application has good mechanical properties, including toughness and average bending strength, which are significantly improved. In addition, the average number of on-off aging of the substrate is significantly increased, and the assembly yield of the substrate is also significantly improved.

[0164] For example, the prepared sample is subjected to high-energy XRF detection, i.e., the element content of the polished sample is tested using an energy dispersive X-ray fluorescence spectrometer EDX-7000. Among them, Zr is 63.9wt%, Y is 5.9wt%, Nb is 0.5wt%, Ba is 1.8wt%, Al is 1.6wt%, and Si is 0.3wt%.

[0165] The prepared sample is subjected to XRD detection to detect the phase, i.e., the phase type is tested using an X-ray diffractometer, including: 93.9wt% of tetragonal zirconia, 0.6wt% of monoclinic zirconia, 3.4wt% of BaAl2O4, and 2.2wt% of mullite phase.

[0166] Of course, the specific content of each element in the zirconia ceramic can be determined by the person skilled in the art according to the actual situation, and is not specifically limited here.

[0167] In one example, the zirconia ceramic contains, in terms of elements: 61.6wt%-66.1wt% of Zr, 5.37wt%-6.46wt% of Y, 0.06wt%-0.97wt% of Nb, 0.89wt%-2.74wt% of Ba, 0.14wt%-0.38wt% of Si, and 0.77wt%-2.18wt% of Al.

[0168] In this example, the above element ratio can further improve the hardness, toughness and average bending strength of the substrate of the oxygen sensor, and the average number of on-off aging of the substrate is also greater, and the assembly yield is higher.

[0169] In one example, the phase of the zirconia ceramic contains: 91wt%-96.5wt% of tetragonal zirconia, 1.67wt%-5.1wt% of barium aluminate, 1.1wt%-2.9wt% of mullite phase, and the remaining phase is monoclinic zirconia.

[0170] In this example, the above phase ratio can further improve the hardness, toughness and average bending strength of the substrate of the oxygen sensor, and the average number of on-off aging of the substrate is also greater, and the assembly yield is higher.

[0171] In this example, the zirconia ceramic can also contain other phases, but it has no negative effect on the zirconia ceramic of the present application. In the present application, the zirconia ceramic contains the above-mentioned phases in the above content based on the zirconia ceramic. The element composition of the zirconia ceramic can also contain other elements, such as oxygen elements, etc.

[0172] In one example, the substrate has a hardness greater than or equal to 1300 Hv, a toughness greater than or equal to 6.5 MPam 0.5 , a bending strength greater than or equal to 820 Mpa, a switching aging number greater than or equal to 10000, and an assembly yield greater than or equal to 94%.

[0173] In one example, the oxygen sensor is stacked with multiple substrates. For example, two or three substrates can be stacked. The number of substrates can be determined by the actual situation and is not limited herein.

[0174] In this example, the oxygen sensor further includes a heater. The oxygen sensor includes three substrates stacked together. 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.

[0175] In this example, the heater is provided with a first insulating layer at both ends facing the first substrate and the second substrate. The opposite ends of the heater are provided with the first insulating layer, which is suitable for insulating the first substrate and the second substrate.

[0176] In this example, the oxygen sensor further includes a reference electrode mounted in the second substrate and electrically connected to the first substrate and the third substrate, respectively. The reference electrode provides a stable reference potential in the oxygen sensor, ensuring the accuracy and stability of the sensor. This stable reference potential enables the oxygen sensor to accurately measure and feedback the oxygen concentration in the exhaust gas.

[0177] In this example, the first substrate is provided with a second insulating layer on the outside, and the second insulating layer avoids the electrodes on the first substrate. The first substrate is provided with a second insulating layer on the outside, which is suitable for insulating external parts, and the second insulating layer can avoid the electrodes on the first substrate.

[0178] In one example, the oxygen sensor is stacked with two substrates, which are a heating layer substrate and a detection layer substrate. The oxygen sensor can also be provided with two substrates, which are a heating layer substrate and a detection layer substrate. The heater is disposed in the heating layer substrate, and the detection layer substrate includes an oxidation layer with a pair of electrodes on both sides and an internal reference gas cavity.

[0179] In this example, the first insulating layer and the second insulating layer are obtained by printing, drying, and sintering slurry with alumina as the base. The surface of the insulating layer is printed with corresponding electrode layers such as heating electrodes, reference electrodes, and external electrodes. The electrodes are obtained by printing, drying, and sintering slurry with platinum powder as the main powder.

[0180] According to another embodiment of the present application, a method for preparing the substrate of the oxygen sensor of the above-mentioned embodiments is provided, the method comprising:

[0181] The raw materials are added to the organic aid for ball milling;

[0182] The binder is added for continued ball milling to obtain a slurry;

[0183] The slurry is cast into a green body;

[0184] The green body is silk-screen printed with electrodes to prepare a green body;

[0185] The green body is sintered to prepare a substrate;

[0186] The raw materials include zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, and barium oxide powder, the yttrium oxide powder accounts for X2 of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies 7.5wt%≤X2≤8.5wt%, the niobium pentoxide powder accounts for M2 of the total amount of the zirconium oxide and the yttrium oxide, and satisfies 7wt%≤X2-0.85M2≤8wt%, and the barium oxide powder accounts for A2 of the total amount of the raw materials, and satisfies 0.5wt%≤A2≤4wt%.

[0187] As shown in FIG. 1, the method for preparing the substrate of the oxygen sensor of the above embodiment includes:

[0188] S21, the raw materials are added to the organic aid for ball milling. For details, refer to step S11, which is not repeated here.

[0189] In this example, the raw materials include zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, aluminum oxide powder, and silicon dioxide. When ball milling, the ball mill tank or sand mill uses an inner lining of zirconium oxide ceramic and zirconium oxide grinding balls to avoid introducing impurities.

[0190] S22, the binder is added for continued ball milling to obtain a slurry. After the raw materials are ball milled in the organic aid for a preset time, the binder is added for continued ball milling to obtain a slurry. For details, refer to step S12, which is not repeated here.

[0191] S23, the slurry is cast into a green body. The slurry obtained by ball milling is cast into a green body through a casting process. For details, refer to step S13, which is not repeated here.

[0192] S24, the green body is silk-screen printed with electrodes to prepare a green body. After the material is discharged and vacuumized, it is cast into a 0.15mm-0.25mm thick film on a steel belt caster. For details, refer to step S14, which is not repeated here.

[0193] S25, the green body is sintered to prepare a substrate. For details, refer to step S15, which is not repeated here.

[0194] In this example, the particle size median of the barium oxide is 0.4-0.8 μm. The barium oxide accounts for A2 of the total amount of the raw materials, and satisfies 1wt%≤A2≤3wt%. By adding the barium oxide content in this range, the hardness, toughness, average bending strength and other mechanical properties of the zirconia ceramic can be further improved.

[0195] In one example, the raw materials further include aluminum oxide powder, and the aluminum oxide powder accounts for B2 of the total amount of the raw materials, and satisfies 1.45:1≤A2:B2≤1.55:1.

[0196] In this example, by limiting the content ratio relationship of Al and Ba in the zirconia ceramic, the performance of the ceramic is improved, and high impact resistance and toughness are achieved. The particle size median of the aluminum oxide is 0.1-0.4 μm. For example, the ratio of the barium oxide powder and the aluminum oxide powder can be 1.45, 1.46, 1.5, 1.52 or 1.55, etc. The person skilled in the art can determine according to the actual situation, which is not specifically limited here.

[0197] In one example, the raw materials further include silicon dioxide, and the silicon dioxide accounts for D2 of the total amount of the raw materials, and satisfies 0≤D2≤1wt%, and 2.5:1≤B2:D2≤2.6:1.

[0198] For example, the content of the silicon dioxide can be 0.1wt%, 0.5wt%, 0.8wt% or 1wt%, etc. The person skilled in the art can determine according to the actual situation, which is not specifically limited here. Moreover, by limiting the content relationship of Al and Si in the zirconia ceramic, the performance of the zirconia ceramic is improved, and high impact resistance and toughness are achieved. The particle size median of the silicon dioxide is 0.1-0.4 μm. The ratio of the aluminum oxide powder and the silicon dioxide can be 2.5, 2.52, 2.54, 2.55, 2.57 or 2.6, etc. The person skilled in the art can determine according to the actual situation, which is not specifically limited here.

[0199] In one example, the silicon dioxide accounts for D2 of the total amount of the raw materials, and satisfies 0.3wt%≤D2≤0.8wt%. By adding the silicon dioxide content in this range, the hardness, toughness, average bending strength and other mechanical properties of the zirconia ceramic can be further improved.

[0200] For example, D2 can be 0.3wt%, 0.5wt%, 0.7wt% or 0.8wt%, etc. The person skilled in the art can determine according to the actual situation, which is not specifically limited here.

[0201] In this example, the particle size median of the yttrium oxide can be 0.5-1 μm. The particle size median of the zirconia is 1-3 μm, and the specific surface area is 5-7 m 2 / g-7m 2Y2O3 powder accounts for X2 of the total amount of ZrO2 powder and Y2O3 powder, and satisfies: 7.5wt%≤X2≤8.5wt%. For example, the content of Y2O3 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. Wherein, the addition of Y2O3 in ZrO2 can stabilize ZrO2.

[0202] In this example, the Y2O3 powder can also be Sm2O3 powder, Er2O3 powder, Sc2O3 powder, Nd2O3 powder, etc. trivalent oxide. Those skilled in the art can determine according to the actual situation, and is not specifically limited here.

[0203] In this example, the Nb2O5 powder accounts for M2 of the total amount of ZrO2 and Y2O3, and satisfies: 7wt%≤X2-0.85M2≤8wt%, and 0.85 is the molecular weight ratio of Y2O3 and Nb2O5. Through the limitation, it is beneficial to improve the performance of the substrate, and has high impact resistance and toughness. X2 and M2 further satisfy: 7.3wt%≤X2-0.85M2≤7.7wt%. For example, X2-0.85M2 can be 7.4wt%, 7.5wt% or 7.6wt%, etc., which can be determined by those skilled in the art according to the actual situation, and is not specifically limited here. Wherein, the particle size median of the Nb2O5 powder is 0.5μm-1μm.

[0204] The application will be described in detail below by way of examples. In the following examples and comparative examples,

[0205] The test data of each example and comparative example is shown in Table 2.

[0206] Example 2-1

[0207] Raw materials: the total mass of the raw materials is positioned at 200g, and ZrO2 powder 86.34wt%, Y2O3 powder 7.5wt%, Nb2O5 powder 0.7wt%, BaO powder 2wt%, Al2O3 powder 2.86wt%, SiO2 powder 0.6wt% are weighed according to the proportion.

[0208] S21, adding raw materials to organic additives for ball milling;

[0209] The above several powders are ball milled in the ball mill tank with organic additives for 12h.

[0210] S22, adding a binder to continue ball milling to obtain a slurry;

[0211] Then 6.65wt% of polyvinyl butyral and DOP are added to the ball mill tank respectively, and the ball milling is continued for 6 hours to obtain a slurry.

[0212] S23, casting the slurry into a green body;

[0213] After ball milling, the slurry was sent into a steel belt casting machine through vacuumizing to prepare a green body with a thickness of 0.15 mm. The temperature zones in the casting process included 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry was dried by passing through multiple temperature zones in turn, which gradually increased, so as to avoid the problem that the surface dries too fast while the inside is not dry.

[0214] The green body was stacked into a thickness of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer, respectively. Then different thicknesses of insulating alumina layer and platinum electrode layer were screen-printed on different layers in turn, and after drying, the different layers were laminated and cold pressed to form the final green body.

[0215] S24, screen-printing electrodes on the green body to prepare a green body;

[0216] The green body was stacked into a thickness of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer, respectively. Then different thicknesses of insulating alumina layer and platinum electrode layer were screen-printed on different layers in turn, and after drying, the different layers were laminated and cold pressed to form the final green body.

[0217] S25, sintering the green body to prepare a substrate;

[0218] The green body was placed into an air sintering furnace, and the temperature was raised from room temperature to 600℃ for 400 min and kept for 2 h, then raised from 600℃ to 1150℃ for 300 min and kept for 2 h, then raised from 1150℃ to 1470℃ for 150 min and kept for 2 h, then lowered from 1470℃ to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and laser cutting of the sintered product, the final sample was prepared, which had a size of 55 mm*4.1 mm*1.1 mm and the side edges were polished and left for testing.

[0219] The sample prepared was detected by high-energy XRF, and the composition elements included: Zr 63.9wt%, Y 5.9wt%, Nb 0.5wt%, Ba 1.8wt%, Al 1.6wt%, Si 0.3wt%.

[0220] XRD detected the phase, i.e., the phase type was tested by an X-ray diffractometer, which included: tetragonal zirconia 93.9wt%, monoclinic zirconia 0.6wt%, BaAl2O4 3.4wt%, and mullite phase 2.2wt%.

[0221] Example 2-2

[0222] Raw materials: the total mass of the raw materials is positioned at 200 g, and zirconium oxide powder (ZrO2) 86.04 wt%, yttrium oxide powder (Y2O3) 7.5 wt%, niobium pentoxide powder (Nb2O5) 1 wt%, barium oxide powder (BaO) 2 wt%, aluminum oxide powder (Al2O3) 2.86 wt%, and silicon dioxide powder (SiO2) 0.6 wt% are weighed according to the proportion.

[0223] S21, adding raw materials to organic additives for ball milling;

[0224] The above several powders are ball milled in a ball milling tank with organic additives for 12 h.

[0225] S22, adding a binder to continue ball milling to obtain a slurry;

[0226] Then 6.65 wt% of polyvinyl butyral and DOP are added to the ball milling tank respectively, and the ball milling is continued for 6 hours to obtain a slurry.

[0227] S23, casting the slurry into a green body;

[0228] After the ball milling is completed, the slurry is sent into a steel belt casting machine through vacuum extraction to be cast, and a green body with a thickness of 0.15 mm is prepared. In the casting process, the temperature zones include 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that gradually increase, which can avoid the problem that the surface dries too quickly and the inside is not dry.

[0229] The green body is stacked into a thickness of 0.6 mm, 0.45 mm, and 0.3 mm as a heating layer, an intermediate layer, and a functional layer respectively. Then different thicknesses of insulating aluminum oxide layers and platinum electrode layers are screen printed on different layers in sequence, and after drying, the different layers are laminated and cold pressed to form a final green body.

[0230] S24, screen printing electrodes on the green body to prepare a green body;

[0231] The green body is stacked into a thickness of 0.6 mm, 0.45 mm, and 0.3 mm as a heating layer, an intermediate layer, and a functional layer respectively. Then different thicknesses of insulating aluminum oxide layers and platinum electrode layers are screen printed on different layers in sequence, and after drying, the different layers are laminated and cold pressed to form a green body.

[0232] S25, sintering the green body to prepare a substrate;

[0233] The green body was put into an air sintering furnace, and was heated from room temperature to 600 DEG C at a rate of 400 min, and was kept at 600 DEG C for 2 hours, and was heated from 600 DEG C to 1150 DEG C at a rate of 300 min, and was kept at 1150 DEG C for 2 hours, and was heated from 1150 DEG C to 1470 DEG C at a rate of 150 min, and was kept at 1470 DEG C for 2 hours, and then was cooled to 900 DEG C at a rate of 150 min, and finally was naturally cooled to room temperature. The sintered product was polished and laser cut to obtain the final sample, and the sample had a size of 55 mm*4.1 mm*1.1 mm, and the side edges were polished and left for testing.

[0234] The prepared sample was detected by high-energy XRF, and the composition elements included: Zr was 63.7 wt%, Y was 5.8 wt%, Nb was 0.7 wt%, Ba was 1.9 wt%, Al was 1.7 wt%, and Si was 0.3 wt%.

[0235] XRD detected the phase, that is, the phase type was tested by using an X-ray diffractometer, and included: 93.9 wt% of tetragonal zirconium oxide, 0.3 wt% of monoclinic zirconium oxide, 3.5 wt% of BaAl2O4, and 2.3 wt% of mullite phase.

[0236] Example 2-3

[0237] Raw materials: the total mass of the raw materials was positioned at 200 g, and the zirconium oxide powder (ZrO2) was 86.34 wt%, the yttrium oxide powder (Y2O3) was 7.5 wt%, the niobium pentoxide powder (Nb2O5) was 0.7 wt%, the barium oxide powder (BaO) was 2.5 wt%, the aluminum oxide powder (Al2O3) was 3.2 wt%, and the silicon dioxide powder (SiO2) was 0.6 wt%.

[0238] S21, the raw materials were added to the organic auxiliary agent for ball milling;

[0239] The above several powders were ball milled in the ball mill tank with the organic auxiliary agent for 12 hours.

[0240] S22, the binder was added for continuous ball milling to obtain a slurry;

[0241] Then, 6.65 wt% of polyvinyl butyral and DOP were added into the ball mill tank respectively, and the ball milling was continued for 6 hours to obtain the slurry.

[0242] S23, the slurry was cast into a green body;

[0243] After the ball milling was completed, the slurry was sent into a steel belt casting machine for casting through vacuumizing, and a green body with a thickness of 0.15 mm was prepared. In the casting process, the temperature zones included 30 DEG C, 45 DEG C, 55 DEG C, 75 DEG C and 85 DEG C. The slurry was dried by sequentially passing through multiple temperature zones which were gradually increased, so that the temperature was not increased too high at one time, and the problem that the surface was dried too fast while the inside was not dry yet could be avoided.

[0244] S24, screen-printing electrodes on the green body to prepare a green body;

[0245] The green body is stacked into thicknesses of 0.6 mm, 0.45 mm and 0.3 mm as the heating layer, the intermediate layer and the functional layer, respectively. Then, different thicknesses of the insulating alumina layer and the platinum electrode layer are screen-printed on different layers in sequence, and after drying, the different layers are stacked and pressed to prepare a green body.

[0246] S25, sintering the green body to prepare a substrate;

[0247] The green body is placed into an air sintering furnace, and the temperature is raised from room temperature to 600°C for 400 min and kept for 2 h, raised from 600°C to 1150°C for 300 min and kept for 2 h, raised from 1150°C to 1470°C for 150 min and kept for 2 h, then lowered to 900°C for 150 min, and finally naturally cooled to room temperature. After polishing and laser cutting, the sintered product is prepared into a final sample, and the sample has a size of 55 mm*4.1 mm*1.1 mm and the side edges are polished and left for testing.

[0248] The sample is detected by high-energy XRF, and the composition elements include: Zr 63.8wt%, Y 5.9wt%, Nb 0.4wt%, Ba 2.4wt%, Al 1.7wt%, and Si 0.3wt%.

[0249] XRD detects the phase, i.e., the phase type is tested by an X-ray diffractometer, including: tetragonal zirconia 92.9wt%, monoclinic zirconia 0.5wt%, BaAl2O4 4.3wt%, and mullite phase 2.3wt%.

[0250] Comparative Example 2-1

[0251] Raw materials: the total mass of the raw materials is positioned at 200 g, and the zirconia powder (ZrO2) 91.71wt%, yttrium oxide powder (Y2O3) 8wt%, and aluminum oxide powder (Al2O3) 0.29wt% are weighed according to the proportion.

[0252] S21, adding raw materials to organic additives for ball milling;

[0253] The above several powders are ball milled in the ball mill tank with organic additives for 12 h.

[0254] S22, adding a binder to continue ball milling to obtain a slurry;

[0255] Then, 6.65wt% of polyvinyl butyral and DOP are added to the ball mill tank respectively, and the ball milling is continued for 6 hours to obtain a slurry.

[0256] S23, the slurry is cast into a green body;

[0257] After ball milling, the slurry is sent into a steel belt casting machine through vacuumizing to prepare a green body with a thickness of 0.15 mm. The temperature zones in the casting process include 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that are gradually increased, which can avoid the problem that the surface is dried too quickly while the inside is not dry enough due to the one-time high temperature increase.

[0258] S24, silk-screening electrodes on the green body to prepare a green body;

[0259] The green body is stacked into a thickness of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer, respectively. Then, different thicknesses of insulating alumina layers and platinum electrode layers are silk-screened on different layers, and after drying, the different layers are stacked and pressed to prepare a green body.

[0260] S25, sintering the green body to prepare a substrate;

[0261] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400 min and kept for 2 h, increased from 600℃ to 1150℃ for 300 min and kept for 2 h, increased from 1150℃ to 1470℃ for 150 min and kept for 2 h, then decreased from 1470℃ to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and laser cutting of the sintered product, the final sample is prepared, which has a size of 55 mm*4.1 mm*1.1 mm and the side edges are polished and left for testing.

[0262] The prepared sample is detected by high-energy XRF, and the composition elements include: Zr is 67.5wt%, Y is 6.5wt%, and Al is 0.3wt%.

[0263] XRD detects the phase, i.e., the phase type is tested by an X-ray diffractometer, which includes: 99.6wt% of tetragonal zirconia and 0.4wt% of monoclinic zirconia.

[0264] Comparative Example 2-2

[0265] Raw materials: the total mass of the raw materials is positioned at 200g, and the zirconia powder (ZrO2) is 91.12wt%, the yttrium oxide powder (Y2O3) is 8wt%, the niobium pentoxide powder (Nb2O5) is 0.59wt%, and the aluminum oxide powder (Al2O3) is 0.29wt%.

[0266] S21, adding the raw materials to the organic auxiliary agent for ball milling;

[0267] The above several powders are ball milled in the ball mill tank with the organic auxiliary agent for 12h.

[0268] S22, continue ball milling by adding a binder to obtain a slurry;

[0269] Then, 6.65wt% of polyvinyl butyral and DOP were added into the ball mill tank respectively, and the ball milling was continued for 6 hours to obtain a slurry.

[0270] S23, the slurry was cast into a green body;

[0271] After the ball milling was completed, the slurry was sent into a steel belt casting machine through vacuum extraction to be cast to prepare a green body with a thickness of 0.15mm. The temperature zones in the casting process included 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry was dried by sequentially passing through multiple temperature zones that gradually increased, which could avoid the problem of the surface drying too quickly while the inside was not dry due to the temperature being increased too high at one time.

[0272] S24, the green body was screen printed with electrodes to prepare a green body;

[0273] The green body was stacked into a thickness of 0.6mm, 0.45mm and 0.3mm as a heating layer, an intermediate layer and a functional layer respectively. Then, different thicknesses of insulating alumina layers and platinum electrode layers were screen printed on different layers in sequence, and after drying, the different layers were stacked and pressed to prepare a green body.

[0274] S25, the green body was sintered to prepare a substrate;

[0275] The green body was placed into an air sintering furnace, and the temperature was increased from room temperature to 600℃ at a rate of 400min and maintained for 2h, increased from 600℃ to 1150℃ at a rate of 300min and maintained for 2h, increased from 1150℃ to 1470℃ at a rate of 150min and maintained for 2h, then decreased from 1470℃ to 900℃ at a rate of 150min, and finally naturally cooled to room temperature. After polishing and laser cutting of the sintered product, the final sample was prepared, and the sample had a size of 55mm*4.1mm*1.1mm and the side edges were polished and left for testing.

[0276] The sample prepared was subjected to high-energy XRF detection, and the composition elements contained Zr 67.5wt%, Y 6.4wt%, Nb 0.5wt%, and Al 0.2wt%.

[0277] XRD detected the phase, i.e., the phase type was tested using an X-ray diffractometer, which included: 98wt% of tetragonal zirconia and 2wt% of monoclinic zirconia.

[0278] Table 2 Mechanical properties of the substrate of the oxygen sensor of the examples and the comparative examples

[0279] In the examples, the data of Examples 2-1 to 2-3 and Comparative Example 2-1 show that the oxygen sensor substrate prepared according to the proportions of Zr, Y, Nb, Ba, Al and Si in the present application has high toughness and average bending strength, a large number of on-off aging times, and a high assembly yield, which can meet the expected requirements. Moreover, compared with Comparative Example 2-1, the hardness of the substrate also has a small difference, which can also meet the expected requirements.

[0280] As can be seen from Table 2, according to the data in Examples 2-1 to 2-3, the oxygen sensor substrate prepared according to the proportions of Zr, Y, Nb, Ba, Al and Si in the present application has high toughness and average bending strength, a large number of on-off aging times, and a high assembly yield, which can meet the expected requirements. Moreover, compared with Comparative Example 2-1, the hardness of the substrate also has a small difference, which can also meet the expected requirements.

[0281] In the examples, the data of Examples 2-1 to 2-3 and Comparative Example 2-1 show that the oxygen sensor substrate prepared according to the proportions of Zr, Y, Nb, Ba, Al and Si in the present application has high toughness and average bending strength, a large number of on-off aging times, and a high assembly yield, which can meet the expected requirements. Moreover, compared with Comparative Example 2-1, the hardness of the substrate also has a small difference, which can also meet the expected requirements.

[0282] In the examples, the data of Examples 2-1 to 2-3 and Comparative Example 2-2 show that in the present application, by adding SiO2 and BaO and preparing SiO2 and BaO with Al2O3 in a certain proportion, the average bending strength, on-off aging times and assembly yield are further improved. The toughness has a small difference, which can also meet the expected requirements.

[0283] The present application also provides another embodiment of the oxygen sensor. The oxygen sensor comprises a substrate, and the substrate has a third zirconia layer. The third zirconia layer contains, in terms of elements, Zr (zirconium), Y (yttrium), Nb (niobium), Si (silicon) and Al (aluminum), and the phase of the third zirconia layer contains tetragonal zirconia, mullite phase, alumina phase and monoclinic zirconia.

[0284] In the examples, the oxygen sensor comprises a substrate, and the third zirconia layer of the substrate contains Zr, Y, Nb, Si and Al, and the phase of the third zirconia layer contains tetragonal zirconia, mullite phase, alumina phase and monoclinic zirconia, so that the substrate of the oxygen sensor in the present application has good mechanical properties. The mechanical properties include toughness and average bending strength, and the number of on-off aging times is significantly improved, and the assembly yield of the substrate is also significantly improved.

[0285] In one example, the third zirconium oxide layer contains, in terms of elements, 52.83wt%-67.45wt% Zr, 4.6wt%-6.6wt% Y, 0.04wt%-1.21wt% Nb, 0.86wt%-4.3wt% La, 0-0.97wt% Si, and 0-7.94wt% Al. And the phase of the third zirconium oxide layer contains 78wt%-98wt% tetragonal zirconium oxide, 1.33wt%-6.56wt% lanthanum aluminate, 0-5.32wt% mullite phase, 0-10wt% alumina phase, and the rest is monoclinic zirconium oxide.

[0286] For example, in this example, the prepared sample is subjected to high-energy XRF detection, i.e., the polished sample is tested for elemental content using an energy dispersive X-ray fluorescence spectrometer EDX-7000. Among them, Zr is 63.5wt%, Y is 5.9wt%, Nb is 0.5wt%, La is 2.2wt%, Al is 1.6wt%, and Si is 0.3wt%.

[0287] The prepared sample is subjected to XRD detection of the phase, i.e., the phase type is tested using an X-ray diffractometer, including: 93.6wt% tetragonal zirconium oxide, 0.7wt% monoclinic zirconium oxide, 3.3wt% LaAlO3, 1.8wt% mullite phase, and 0.6wt% alumina.

[0288] Of course, the specific content of each element in the third zirconium oxide layer can be determined by the person skilled in the art according to the actual situation, and is not specifically limited here.

[0289] In one example, the third zirconium oxide layer contains, in terms of elements, 56.9wt%-67.11wt% Zr, 4.9wt%-6.5wt% Y, 0.05wt%-0.97wt% Nb, 1.26wt%-2.98wt% La, 0.01wt%-0.46wt% Si, and 0-5.6wt% Al.

[0290] In this example, the above-mentioned element ratio can further improve the hardness, toughness and average bending strength of the substrate, and the average number of on-off aging of the substrate is also greater, and the assembly yield is higher.

[0291] In one example, the phase of the third zirconium oxide layer contains 84.5wt%-97.5wt% tetragonal zirconium oxide, 1.95wt%-4.6wt% lanthanum aluminate, 0.07wt%-3.55wt% mullite phase, 0-7wt% alumina phase, and the rest is monoclinic zirconium oxide.

[0292] In this example, the above-mentioned phase ratio can further improve the hardness, toughness and average bending strength of the substrate of the oxygen sensor, and the average number of times of on-off aging of the substrate is also greater, and the assembly yield is higher.

[0293] In this example, the third zirconia layer can also contain other phases, but has no negative effect on the substrate of the present application. In the present application, the third zirconia layer can also contain other elements, such as oxygen elements, etc.

[0294] In one example, the third zirconia layer contains, in terms of elements: 52.46wt%-67.45wt% of Zr, 4.5wt%-6.6wt% of Y, 0.04wt%-1.21wt% of Nb, 0.23wt%-2.3wt% of Si, and 0.088wt%-7.94wt% of Al. The phase of the third zirconia layer contains: 77.5wt%-98wt% of tetragonal zirconia, 0-13.28wt% of ZrSiO4, 0.24wt%-17.85wt% of mullite phase, 0-2.15wt% of alumina phase, and the remaining phase is monoclinic phase.

[0295] In this example, the third zirconia layer has the above-mentioned element content, so that the mechanical properties of the substrate can be significantly improved. That is, the substrate can have higher hardness, toughness and average bending strength, and the average number of times of on-off aging is also greater, which is also beneficial to improve the assembly yield.

[0296] In one example, the third zirconia layer contains, in terms of elements: 57.9wt%-66.4wt% of Zr, 4.9wt%-6.4wt% of Y, 0.05wt%-0.96wt% of Nb, 0.46-1.38wt% of Si, and 0.18-4.76wt% of Al. The phase of the third zirconia layer contains: 86wt%-97wt% of tetragonal zirconia, 0-7.97wt% of zirconium silicate, 0.48wt%-10.71wt% of mullite phase, 0-1.29wt% of alumina phase, and the remaining phase is monoclinic zirconia.

[0297] In this example, the above-mentioned element and phase ratio can further improve the hardness, toughness and average bending strength of the substrate, and the average number of times of on-off aging of the substrate is also greater.

[0298] In this example, the third zirconia layer can be formed by casting zirconia powder, niobium pentoxide powder, yttrium oxide powder, silicon dioxide powder, and aluminum oxide powder. The silicon dioxide powder accounts for 0.5wt% to 5wt% of the total amount, for example, 1wt% to 3wt%. The niobium pentoxide powder accounts for M of the total amount of zirconia powder and yttrium oxide powder, and the ratio of M to aluminum oxide powder is 1 to 3, for example, 1.5 to 2.5.

[0299] In one example, the third zirconia layer contains the elements and phases of the above embodiments, the hardness of the substrate is greater than or equal to 1250Hv, the toughness of the substrate is greater than or equal to 6.5MPam 0.5 , the bending strength of the substrate is greater than or equal to 800Mpa, the on-off aging number of the substrate is greater than or equal to 10000, and the assembly yield of the substrate is greater than or equal to 95%.

[0300] In one example, the oxygen sensor is stacked with multiple layers of substrates. For example, two or three layers of substrates can be provided. The skilled person can determine the actual situation, and this is not specifically limited here.

[0301] In this example, the oxygen sensor also includes a heater. The oxygen sensor includes three layers of substrates stacked together, the 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.

[0302] In this example, the heater is provided with a first insulating layer at both ends facing the first substrate and the second substrate. The opposite ends of the heater are provided with a first insulating layer, which is suitable for insulating the first substrate and the second substrate.

[0303] In this example, the oxygen sensor also includes a reference electrode, which is installed in the second substrate and is electrically connected to the first substrate and the third substrate respectively. The reference electrode provides a stable reference potential in the oxygen sensor, ensuring the accuracy and stability of the sensor. This stable reference potential enables the oxygen sensor to accurately measure and feedback the oxygen concentration in the exhaust gas.

[0304] In this example, the first substrate is provided with a second insulating layer on the outside, and the second insulating layer avoids the electrodes on the first substrate. The first substrate is provided with a second insulating layer on the outside, which is suitable for insulating external parts, and the second insulating layer can avoid the electrodes on the first substrate.

[0305] In one example, the oxygen sensor is stacked with two layers of substrates, which are heating layer substrate and detection layer substrate respectively. The oxygen sensor can also be provided with two layers of substrates, which are heating layer substrate and detection layer substrate respectively. The heater is arranged in the heating layer substrate, and the detection layer substrate includes a pair of electrodes on both sides of the zirconia layer and an internal reference gas cavity.

[0306] In this example, the first and second insulating layers are alumina-based slurry printed, dried, sintered. The insulating layer surface is printed with corresponding electrode layers such as heating electrode, reference electrode and outer electrode, which are all platinum powder-based slurry printed, dried and sintered.

[0307] According to another embodiment of the present application, a method for preparing the substrate of the oxygen sensor of the above-mentioned embodiments is provided, the method comprising:

[0308] adding raw materials to the organic auxiliary agent for ball milling;

[0309] adding a binder for continuous ball milling to obtain a slurry;

[0310] flow casting the slurry into a green body;

[0311] screen printing electrodes on the green body to prepare a green body;

[0312] sintering the green body to prepare a substrate;

[0313] The raw materials include zirconium oxide powder, yttrium oxide powder and niobium pentoxide powder, the yttrium oxide powder accounts for X3 of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies: 7.5wt%≤X3≤8.5wt%, the niobium pentoxide powder accounts for M3 of the total amount of the zirconium oxide and the yttrium oxide, and satisfies: 7wt%≤X3-0.85M3≤8wt%.

[0314] As shown in FIG. 1, the method for preparing the substrate of the oxygen sensor of the above-mentioned embodiments comprises:

[0315] S31, adding raw materials to the organic auxiliary agent for ball milling. For details, refer to step S11, which will not be repeated here.

[0316] In this example, the raw materials include zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, aluminum oxide powder and silicon dioxide. When ball milling, the ball mill tank or sand mill uses zirconia ceramic lining and zirconia grinding balls to avoid introducing impurities.

[0317] S32, adding a binder for continuous ball milling to obtain a slurry. After the raw materials are ball milled in the organic auxiliary agent for a predetermined time, a binder is added for continuous ball milling to obtain a slurry. For details, refer to step S12, which will not be repeated here.

[0318] S33, flow casting the slurry into a green body. The slurry obtained by ball milling is flow cast into a green body by flow casting process. For details, refer to step S13, which will not be repeated here.

[0319] S34, screen printing electrodes on the green body to prepare a green body. After discharging and vacuumizing, the steel belt flow casting machine is used to flow cast a 0.15mm-0.25mm thick film. For details, refer to step S14, which will not be repeated here.

[0320] S35, sintering the green body to produce a substrate. Details can refer to step S15, which will not be repeated here.

[0321] In one example, the raw material further includes lanthanum oxide powder, and the lanthanum oxide powder accounts for A3 of the total amount of the raw material, which satisfies 1wt%≤A3≤5wt%. The median particle size of the lanthanum oxide is 0.3μm-0.6μm. The lanthanum oxide accounts for A3 of the total amount of the raw material, which satisfies 1wt%≤A3≤3wt%. For example, further, 1.5wt%≤A3≤3.5wt%. By adding the content of lanthanum oxide in this range, the mechanical properties of the substrate such as hardness, toughness, and average bending strength can be further improved.

[0322] In one example, the raw material further includes aluminum oxide powder, and the aluminum oxide powder accounts for B3 of the total amount of the raw material, which satisfies 1:3≤A3:B3≤3:1.

[0323] In this example, by limiting the content ratio relationship of Al and La in the raw material, the performance of the substrate can be improved, and high impact resistance and toughness are combined. The median particle size of the aluminum oxide is 0.1μm-0.4μm. For example, the ratio of the lanthanum oxide powder and the aluminum oxide powder can be 0.4, 0.6, 1, 1.5, 2, or 3, etc. Those skilled in the art can determine according to the actual situation, which will not be specifically limited here.

[0324] In one example, the raw material further includes silicon dioxide, and the silicon dioxide accounts for D3 of the total amount of the raw material, which satisfies 0≤D3≤1.5wt%.

[0325] For example, the content of the silicon dioxide can be 0.1wt%, 0.5wt%, 0.8wt%, 1wt%, or 1.5wt%, etc. Those skilled in the art can determine according to the actual situation, which will not be specifically limited here. Moreover, by limiting the content relationship of Al and Si in the raw material, the performance of the substrate can be improved, and high impact resistance and toughness are combined. The median particle size of the silicon dioxide is 0.1μm-0.4μm.

[0326] In one example, the silicon dioxide accounts for D3 of the total amount of the raw material, and D3 satisfies 0.02wt%≤D3≤1wt%. By adding the content of silicon dioxide in this range, the mechanical properties of the substrate such as hardness, toughness, and average bending strength can be further improved.

[0327] For example, D3 can further be 0.3wt%, 0.5wt%, 0.7wt%, or 0.8wt%, etc. Those skilled in the art can determine according to the actual situation, which will not be specifically limited here.

[0328] In one example, the yttrium oxide powder accounts for X3 of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies 7.5wt%≤X3≤8.5wt%.

[0329] In this example, the particle size median of the yttrium oxide can be 0.5μm-1μm. The particle size median of the zirconium oxide is 1μm-3μm, and the specific surface area is 5m 2 / g-7m 2 / g. The yttrium oxide powder accounts for X of the total amount of the zirconium oxide powder and the yttrium oxide powder, and satisfies 7.5wt%≤X≤8.5wt%. For example, the content of the 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 yttrium oxide added in the zirconium oxide can stabilize the zirconium oxide.

[0330] In this example, the yttrium oxide powder can also be samarium oxide powder, erbium oxide powder, scandium oxide powder, neodymium oxide powder, etc. trivalent oxide. Those skilled in the art can determine according to the actual situation, and is not specifically limited here.

[0331] In one example, the niobium pentoxide powder accounts for M3 of the total amount of the zirconium oxide and the yttrium oxide, and satisfies 7wt%≤X3-0.85M3≤8wt%, and 0.85 is the molecular weight ratio of yttrium oxide and niobium pentoxide. Through the limitation, it is beneficial to improve the performance of the substrate, and has high impact resistance and toughness. X3 and M3 further satisfy 7.3wt%≤X3-0.85M3≤7.7wt%. Among them, the particle size median of the niobium pentoxide powder is 0.5μm-1μm. The following will be described in detail through examples. In the following examples and comparative examples,

[0332] The test data of each example and comparative example is shown in Table 3.

[0333] Example 3-1

[0334] Raw materials: the total mass of the raw materials is positioned at 200g, and the zirconium oxide powder (ZrO2) 85.8wt%, the yttrium oxide powder (Y2O3) 7.5wt%, the niobium pentoxide powder (Nb2O5) 0.7wt%, the lanthanum oxide powder (La2O3) 2.5wt%, the aluminum oxide powder (Al2O3) 3wt%, and the silicon dioxide powder (SiO2) 0.5wt% are weighed according to the proportion.

[0335] S31, adding the raw materials to the organic auxiliary agent for ball milling;

[0336] The above several powders are ball milled in the ball milling tank with the organic auxiliary agent for 12h.

[0337] S32, adding the binder for continuous ball milling to obtain the slurry;

[0338] Then 6.65wt% of polyvinyl butyral and DOP were added into the ball mill tank respectively, and the ball milling was continued for 6 hours to obtain the slurry.

[0339] S33, the slurry was cast into a green body;

[0340] After the ball milling, the slurry was sent into a steel belt casting machine through vacuum extraction to be cast to prepare a green body with a thickness of 0.15mm. The temperature zones in the casting process included 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry was dried by sequentially passing through multiple temperature zones which were gradually increased, so as to avoid the problem that the surface is dried too fast while the inside is not dry due to the temperature being increased too high at one time.

[0341] S34, the green body was silk-screened with electrodes to prepare a green body;

[0342] The green body was stacked into a thickness of 0.6mm, 0.45mm and 0.3mm as a heating layer, an intermediate layer and a functional layer respectively. Then different thicknesses of insulating alumina layer and platinum electrode layer were silk-screened on different layers in sequence, and after drying, the different layers were stacked and pressed to prepare a green body.

[0343] S35, the green body was sintered to prepare a substrate;

[0344] The green body was put into an air sintering furnace, and the temperature was increased from room temperature to 600℃ for 400min and kept for 2h, increased from 600℃ to 1150℃ for 300min and kept for 2h, increased from 1150℃ to 1470℃ for 150min and kept for 2h, then decreased from 1470℃ to 900℃ for 150min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product and laser cutting, the final sample was prepared, and the sample had a size of 55mm*4.1mm*1.1mm and the side was polished and polished to be left for testing.

[0345] The prepared sample was detected by high-energy XRF, and the composition elements contained: Zr was 63.5wt%, Y was 5.9wt%, Nb was 0.5wt%, La was 2.2wt%, Al was 1.6wt%, and Si was 0.3wt%.

[0346] XRD detected the phase, that is, the phase type was tested by using an X-ray diffractometer, including: 93.6wt% of tetragonal zirconia, 0.7wt% of monoclinic zirconia, 3.3wt% of LaAlO3, 1.8wt% of mullite phase, and 0.6wt% of aluminum oxide.

[0347] Example 3-2

[0348] Raw materials: the total mass of the raw materials is positioned at 200 g, and zirconium oxide powder (ZrO2) 85.5 wt%, yttrium oxide powder (Y2O3) 7.5 wt%, niobium pentoxide powder (Nb2O5) 1 wt%, lanthanum oxide powder (La2O3) 2.5 wt%, aluminum oxide powder (Al2O3) 3 wt%, and silicon dioxide powder (SiO2) 0.5 wt% are weighed according to the proportion.

[0349] S31, adding raw materials to organic additives for ball milling;

[0350] The above several powders are ball milled in a ball mill tank with organic additives for 12 h.

[0351] S32, adding a binder to continue ball milling to obtain a slurry;

[0352] Then 6.65 wt% of polyvinyl butyral and DOP are added to the ball mill tank respectively, and the ball milling is continued for 6 hours to obtain a slurry.

[0353] S33, the slurry is cast into a green body;

[0354] After the ball milling is completed, the slurry is sent into a steel belt casting machine for casting by vacuumizing, and a green body with a thickness of 0.15 mm is prepared. In the casting process, the temperature zones include 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that gradually increase, which can avoid the problem that the surface dries too quickly and the inside is not dry enough due to the temperature increasing too high at one time.

[0355] S34, printing electrodes on the green body to prepare a green body;

[0356] The green body is stacked into a thickness of 0.6 mm, 0.45 mm, and 0.3 mm as a heating layer, an intermediate layer, and a functional layer, respectively. Then different thicknesses of insulating alumina layers and platinum electrode layers are printed on different layers in sequence, and after drying, the different layers are stacked and pressed to prepare a green body.

[0357] S35, sintering the green body to prepare a substrate;

[0358] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400 min and kept for 2 h, increased from 600℃ to 1150℃ for 300 min and kept for 2 h, increased from 1150℃ to 1470℃ for 150 min and kept for 2 h, then decreased from 1470℃ to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product, and laser cutting, the final sample is prepared, and the sample has a size of 55 mm*4.1 mm*1.1 mm and the side edges are polished and polished to be left for testing.

[0359] The prepared sample is subjected to high-energy XRF detection, and the composition elements include: Zr 67.4wt%, Y 5.8wt%, Nb 0.7wt%, La 2.4wt%, Al 1.5wt%, Si 0.2wt%.

[0360] XRD detects the phase, that is, the phase type is tested by using an X-ray diffractometer, including: 93.7wt% of tetragonal zirconium oxide, 0.7wt% of monoclinic zirconium oxide, 3.4wt% of LaAlO3, 1.7wt% of mullite phase, and 0.5wt% of aluminum oxide.

[0361] Example 3-3

[0362] Raw materials: the total mass of the raw materials is positioned at 200g, and the zirconium oxide powder (ZrO2) 85.3wt%, yttrium oxide powder (Y2O3) 7.5wt%, niobium pentoxide powder (Nb2O5) 0.7wt%, lanthanum oxide powder (La2O3) 3wt%, aluminum oxide powder (Al2O3) 3wt%, and silicon dioxide powder (SiO2) 0.5wt% are weighed according to the proportion.

[0363] S31, the raw materials are added to the organic auxiliary agent for ball milling;

[0364] The above several powders are ball milled in the ball milling tank with the organic auxiliary agent for 12h.

[0365] S32, the binder is added for continuous ball milling to obtain a slurry;

[0366] Then, 6.65wt% of polyvinyl butyral and DOP are added into the ball milling tank respectively, and the ball milling is continued for 6 hours to obtain the slurry.

[0367] S33, the slurry is cast into a green body;

[0368] After the ball milling is completed, the slurry is sent into a steel belt casting machine for casting after vacuumizing, and a green body with a thickness of 0.15mm is prepared. In the casting process, the temperature zones include 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry is dried by sequentially passing through multiple temperature zones which are gradually increased, so that the temperature is not increased too high at one time, and the problem that the surface is dried too fast while the inside is not dry yet can be avoided.

[0369] S34, the green body is silk-screened with electrodes to prepare a green body;

[0370] The green body is stacked into a thickness of 0.6mm, 0.45mm, and 0.3mm as a heating layer, an intermediate layer, and a functional layer respectively. Then, different thicknesses of insulating aluminum oxide layers and platinum electrode layers are silk-screened on different layers in sequence, and after drying, the different layers are stacked and pressed to prepare a green body.

[0371] S35, the green body is sintered to prepare a substrate;

[0372] The green body was put into an air sintering furnace, and heated from room temperature to 600 DEG C at a rate of 400 min, and kept for 2 h, heated from 600 DEG C to 1150 DEG C at a rate of 300 min, and kept for 2 h, heated from 1150 DEG C to 1470 DEG C at a rate of 150 min, and kept for 2 h, then cooled to 900 DEG C at a rate of 150 min, and finally naturally cooled to room temperature. The sintered product was polished and laser cut to form the final sample, and the sample had a size of 55 mm*4.1 mm*1.1 mm, and the side edges were polished and left for testing.

[0373] The prepared sample was detected by high-energy XRF, and the composition elements included: Zr 63.2wt%, Y 6.1wt%, Nb 0.7wt%, La 2.6wt%, Al 1.7wt%, Si 0.2wt%.

[0374] XRD detected the phase, that is, the phase type was tested by an X-ray diffractometer, and included: tetragonal zirconia 93.3wt%, monoclinic zirconia 0.8wt%, LaAlO3 3.9wt%, mullite phase 1.7wt%, and aluminum oxide 0.3wt%.

[0375] Example 3-4

[0376] Raw materials: the total raw material mass was 200 g, and zirconium oxide (ZrO2) 87.8wt%, yttrium oxide (Y2O3) 7.5wt%, niobium pentoxide (Nb2O5) 0.7wt%, aluminum oxide (Al2O3) 2wt%, and silicon dioxide (SiO2) 2wt% were weighed according to the proportion.

[0377] S31, the raw materials were added to the organic auxiliary agent for ball milling;

[0378] The above several powders were ball milled in the ball mill tank with the organic auxiliary agent for 12 h.

[0379] S32, the binder was added for continuous ball milling to obtain a slurry;

[0380] Then 5.65wt% of polyvinyl butyral and DOP were added into the ball mill tank respectively, and the ball milling was continued for 5 hours to obtain the slurry.

[0381] S33, the slurry was cast into a green body;

[0382] After the ball milling was completed, the slurry was sent into a steel belt casting machine for casting after vacuumizing, and a green body with a thickness of 0.15 mm was prepared. In the casting process, the temperature zones included 30 DEG C, 45 DEG C, 55 DEG C, 75 DEG C, and 85 DEG C. The slurry was dried by sequentially passing through multiple temperature zones which were gradually increased, so that the temperature was not increased too high at one time, and the problem that the surface was dried too fast while the inside was not dry yet could be avoided.

[0383] S34, screen-printing electrodes on the green body to prepare a green body;

[0384] The green body is stacked into thicknesses of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer, respectively. Then, different thicknesses of insulating alumina layers and platinum electrode layers are screen-printed on different layers in sequence, and after drying, the different layers are stacked and pressed into a green body.

[0385] S35, sintering the green body to prepare a substrate;

[0386] The green body is placed into an air sintering furnace, and the temperature is raised from room temperature to 600 DEG C at a rate of 400 min, and then kept for 2 h, raised from 600 DEG C to 1150 DEG C at a rate of 300 min, and then kept for 2 h, raised from 1150 DEG C to 1470 DEG C at a rate of 150 min, and then kept for 2 h, then lowered to 900 DEG C at a rate of 150 min, and finally naturally cooled to room temperature. After polishing and laser cutting, the sintered product is prepared into a final sample, and the sample has a size of 55 mm*4.1 mm*1.1 mm, and the side edges are polished and left for testing.

[0387] The sample is detected by high-energy XRF, and the composition elements include: Zr is 64.6wt%, Y is 5.8wt%, Nb is 0.5wt%, Al is 1.1wt%, and Si is 0.9wt%.

[0388] XRD detects the phase, that is, the phase type is tested by an X-ray diffractometer, including: 93.2wt% of tetragonal zirconia, 0.5wt% of monoclinic zirconia, 3.6wt% of ZrSiO4, and 2.7wt% of mullite phase.

[0389] Examples 3-5

[0390] Raw materials: the total raw material mass is 200 g, and zirconia (ZrO2) is 89.8wt%, yttrium oxide (Y2O3) is 7.5wt%, niobium pentoxide (Nb2O5) is 0.7wt%, aluminum oxide (Al2O3) is 1wt%, and silicon dioxide (SiO2) is 1wt%.

[0391] S31, adding raw materials to organic additives for ball milling;

[0392] The several powders are ball milled in the ball mill tank for 12 h with organic additives.

[0393] S32, adding a binder to continue ball milling to obtain a slurry;

[0394] Then, 5.65wt% of polyvinyl butyral and DOP are added to the ball mill tank respectively, and the ball milling is continued for 5 hours to obtain a slurry.

[0395] S33, the slurry is cast into a green body;

[0396] After ball milling, the slurry is sent into a steel belt casting machine for casting by vacuumizing to prepare a green body with a thickness of 0.15 mm. The temperature zones in the casting process include 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that are gradually increased, which can avoid the problem of too fast surface drying and internal drying.

[0397] S34, the green body is silk-screened with electrodes to prepare a green body;

[0398] The green body is stacked into a thickness of 0.6 mm, 0.45 mm and 0.3 mm as a heating layer, an intermediate layer and a functional layer. Then, different thicknesses of insulating alumina layers and platinum electrode layers are silk-screened on different layers, and after drying, the different layers are stacked and pressed to prepare a green body.

[0399] S35, the green body is sintered to prepare a substrate;

[0400] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400 min and kept for 2 h, increased from 600℃ to 1150℃ for 300 min and kept for 2 h, increased from 1150℃ to 1470℃ for 150 min and kept for 2 h, then decreased to 900℃ for 150 min, and finally naturally cooled to room temperature. After polishing and laser cutting of the sintered product, the final sample is prepared, and the sample has a size of 55 mm*4.1 mm*1.1 mm and the side edges are polished and left for testing.

[0401] The sample prepared is detected by high-energy XRF, and the composition elements include: Zr 66.4wt%, Y 5.9wt%, Nb 0.6wt%, Al 0.6wt%, Si 0.5wt%.

[0402] The phase detected by XRD includes: 96.5wt% of tetragonal zirconia, 0.3wt% of monoclinic zirconia, 1.8wt% of ZrSiO4, and 1.4wt% of mullite phase.

[0403] Examples 3-6

[0404] Raw materials: the total raw material mass is 200 g, and zirconia (ZrO2) 85.8wt%, yttrium oxide (Y2O3) 7.5wt%, niobium pentoxide (Nb2O5) 0.7wt%, aluminum oxide (Al2O3) 3wt%, and silicon dioxide (SiO2) 3wt% are weighed according to the proportion.

[0405] S31, the raw materials are added to the organic auxiliary agent for ball milling;

[0406] The above several powders are ball milled in a ball mill tank with an organic additive for 12 hours.

[0407] S32, adding a binder to continue ball milling to obtain a slurry;

[0408] Then 5.65wt% of polyvinyl butyral and DOP are added to the ball mill tank respectively, and the ball milling is continued for 5 hours to obtain a slurry.

[0409] S33, the slurry is cast into a green body;

[0410] After the ball milling is completed, the slurry is sent into a steel belt casting machine through vacuum extraction for casting to prepare a green body with a thickness of 0.15mm. In the casting process, the temperature zones include 30℃, 45℃, 55℃, 75℃ and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that gradually increase, which can avoid the problem of too fast surface drying and internal drying.

[0411] S34, the green body is silk-screened with electrodes to prepare a green body;

[0412] The green body is stacked into a thickness of 0.6mm, 0.45mm and 0.3mm as a heating layer, an intermediate layer and a functional layer respectively. Then different thicknesses of insulating alumina layers and platinum electrode layers are silk-screened on different layers in sequence, and after drying, the different layers are stacked and pressed to prepare a green body.

[0413] S35, the green body is sintered to prepare a substrate;

[0414] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400min and kept for 2h, increased from 600℃ to 1150℃ for 300min and kept for 2h, increased from 1150℃ to 1470℃ for 150min and kept for 2h, then decreased from 1470℃ to 900℃ for 150min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product, and laser cutting, the final sample is prepared, and the sample has a size of 55mm*4.1mm*1.1mm and the side edges are polished and polished to be left for testing.

[0415] The sample prepared is detected by high-energy XRF, and the composition elements contain: Zr is 63.5wt%, Y is 5.7wt%, Nb is 0.4wt%, Al is 1.6wt%, and Si is 1.5wt%.

[0416] The phase detected by XRD includes: tetragonal zirconia is 89.5wt%, monoclinic zirconia is 0.6wt%, ZrSiO4 is 5.6wt%, and mullite phase is 4.3wt%.

[0417] Comparative Example 3-1

[0418] Raw materials: The total mass of the raw materials is positioned at 200g, and zirconium oxide powder (ZrO2) 91.71wt%, yttrium oxide powder (Y2O3) 8wt%, and niobium pentoxide powder (Nb2O5) 0.29wt% are weighed according to the proportion.

[0419] S31, adding raw materials to organic additives for ball milling;

[0420] The above several powders are ball milled in a ball milling tank with organic additives for 12h.

[0421] S32, adding a binder to continue ball milling to obtain a slurry;

[0422] Then 6.65wt% of polyvinyl butyral and DOP are added to the ball milling tank respectively, and the ball milling is continued for 6h to obtain a slurry.

[0423] S33, the slurry is cast into a green body;

[0424] After the ball milling is completed, the slurry is sent into a steel belt casting machine for casting by vacuumizing, and a green body with a thickness of 0.15mm is prepared. In the casting process, the temperature zones include 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry is dried by sequentially passing through multiple temperature zones that are gradually increased, which can avoid the problem that the surface is dried too quickly and the inside is not dry enough due to the temperature being increased too high at one time.

[0425] S34, the green body is silk-screened with electrodes to prepare a green body;

[0426] The green body is stacked into a thickness of 0.6mm, 0.45mm, and 0.3mm as a heating layer, an intermediate layer, and a functional layer respectively. Then different thicknesses of insulating alumina layers and platinum electrode layers are silk-screened on different layers in sequence, and after drying, the different layers are stacked and pressed to prepare a green body.

[0427] S35, sintering the green body to prepare a substrate;

[0428] The green body is placed into an air sintering furnace, and the temperature is increased from room temperature to 600℃ for 400min and kept for 2h, increased from 600℃ to 1150℃ for 300min and kept for 2h, increased from 1150℃ to 1470℃ for 150min and kept for 2h, then decreased to 900℃ for 150min, and finally naturally cooled to room temperature. After polishing and polishing of the sintered product, and laser cutting, the final sample is prepared, and the sample has a size of 55mm*4.1mm*1.1mm and the side edges are polished and polished to be left for testing.

[0429] The prepared sample is detected by high-energy XRF, and the composition elements contain: Zr is 67.5wt%, Y is 6.5wt%, and Al is 0.3wt%.

[0430] XRD detected the phase, that is, the phase type was tested using an X-ray diffractometer, including: 99.6wt% of tetragonal zirconium oxide, 0.4wt% of monoclinic zirconium oxide.

[0431] Comparative Example 3-2

[0432] Raw materials: the total mass of the raw materials was positioned at 200g, and zirconium oxide powder (ZrO2) 91.12wt%, yttrium oxide powder (Y2O3) 8wt%, niobium pentoxide powder (Nb2O5) 0.59wt%, and aluminum oxide powder (Al2O3) 0.29wt% were weighed according to the proportion.

[0433] S31, the raw materials were added to the organic auxiliary agent for ball milling;

[0434] The above several powders were ball milled in the ball mill tank with the organic auxiliary agent for 12h.

[0435] S32, a binder was added for continuous ball milling to obtain a slurry;

[0436] Then 6.65wt% of polyvinyl butyral and DOP were added to the ball mill tank respectively, and the ball milling was continued for 6 hours to obtain a slurry.

[0437] S33, the slurry was cast into a green body;

[0438] After the ball milling was completed, the slurry was sent into a steel belt casting machine for casting by vacuumizing, and a green body with a thickness of 0.15mm was prepared. In the casting process, the temperature zones included 30℃, 45℃, 55℃, 75℃, and 85℃. The slurry was dried by sequentially passing through multiple temperature zones which were gradually increased, so that the temperature was not increased too high at one time, and the problem of too fast surface drying and internal drying was avoided.

[0439] S34, the green body was silk-screen printed with electrodes to prepare a green body;

[0440] The green body was stacked into a thickness of 0.6mm, 0.45mm and 0.3mm as a heating layer, an intermediate layer and a functional layer respectively. Then different thicknesses of insulating aluminum oxide layers and platinum electrode layers were silk-screen printed on different layers in turn, and after drying, the different layers were stacked and pressed to prepare a green body.

[0441] S35, the green body was sintered to prepare a substrate;

[0442] The green body was put into an air sintering furnace, and heated from room temperature to 600℃ for 400min and kept for 2h, heated from 600℃ to 1150℃ for 300min and kept for 2h, heated from 1150℃ to 1470℃ for 150min and kept for 2h, then cooled to 900℃ for 150min, and finally naturally cooled to room temperature. After polishing and laser cutting of the sintered product, the final sample was prepared, and the sample had a size of 55mm*4.1mm*1.1mm and the side edges were polished and left for testing.

[0443] The prepared sample was detected by high-energy XRF, and the composition elements contained: Zr was 67.5wt%, Y was 6.4wt%, Nb was 0.5wt%, and Al was 0.2wt%.

[0444] XRD detected the phase, that is, the phase type was tested by an X-ray diffractometer, including: 98wt% of tetragonal zirconium oxide and 2wt% of monoclinic zirconium oxide.

[0445] Table 3 mechanical properties of the substrate of the oxygen sensor of the examples and the comparative examples

[0446] Among them, examples 3-1 to 3-3 are the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, lanthanum oxide powder, aluminum oxide powder and silicon dioxide powder in proportion. Examples 3-4 to 3-5 are the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder, aluminum oxide powder and silicon dioxide powder in proportion. Comparative example 3-1 is the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder and aluminum oxide powder in proportion. Comparative example 3-2 is the data of the substrate prepared by weighing the zirconium oxide powder, yttrium oxide powder, niobium pentoxide powder and aluminum oxide powder in proportion.

[0447] From table 3, according to the data in examples 3-1, 3-2 and 3-3, the oxygen sensor substrate prepared according to the proportion of Zr, Y, Nb, La, Al and Si in this application has high toughness and average bending strength, and the on-off aging frequency is also large, the assembly yield is high, and can meet the expected requirements. And compared with comparative example 1, the hardness of the substrate is also small, which can also meet the expected requirements.

[0448] According to the data in Example 3-4, Example 3-5 and Example 3-6, the Zr, Y, Nb, Al and Si elements in the present application are proportioned and the substrate prepared by the preparation method in the present application has good mechanical properties. That is, the substrate also has high toughness and average bending strength, and the on-off aging times are also large, the assembly yield is high, and the expected requirements can be met. And compared with Comparative Example 3-1, the hardness of the substrate also differs little, and the expected requirements can also be met.

[0449] Comparing the data of Example 3-1 to Example 3-3 with Comparative Example 3-1, it can be seen that by adding niobium pentoxide, silicon dioxide and lanthanum oxide in the present application, and proportioning them, the oxygen sensor substrate can have high toughness and average bending strength, and the on-off aging times and assembly yield are also significantly improved.

[0450] Comparing the data of Example 3-1 to Example 3-3 and Comparative Example 3-2, it can be seen that in the present application, by adding silicon dioxide and lanthanum oxide, and proportioning the silicon dioxide and lanthanum oxide with aluminum oxide, it is beneficial to further improve the average bending strength, on-off aging times and assembly yield. The toughness is slightly reduced, but it can also meet the expected requirements.

[0451] Comparing the data of Example 3-4 to Example 3-6 with Comparative Example 3-1, it can be seen that by adding niobium pentoxide and silicon dioxide in the present application, and proportioning them, the substrate of the oxygen sensor can have high toughness and average bending strength, and the on-off aging times and assembly yield are also significantly improved.

[0452] Comparing the data of Example 3-4 to Example 3-6 and Comparative Example 3-2, it can be seen that in the present application, by adding silicon dioxide, and proportioning the silicon dioxide and aluminum oxide, it is beneficial to further improve the average bending strength, on-off aging times and assembly yield.

[0453] The above examples focus on the differences between the various embodiments, and the different optimization features between the various embodiments can be combined to form a more optimal embodiment as long as they are not contradictory. Considering the brevity of the writing, it will not be repeated here.

[0454] Although some specific embodiments of the present application have been described in detail through examples, those skilled in the art should understand that the above examples are only for illustration, not for limiting the scope of the present application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope and spirit of the present application. The scope of the present application is defined by the appended claims.

Claims

1. An oxygen sensor, wherein, The substrate comprises a zirconia layer; The zirconia layer comprises, in terms of elements, Zr, a trivalent element, Nb and Al; The phase of the zirconia layer comprises 96wt%-99.7wt% of tetragonal zirconia, and the rest is monoclinic zirconia, wherein the ratio of the molar content of the trivalent element oxide to the total molar content of zirconia, trivalent element oxide and niobium oxide in the tetragonal zirconia 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, trivalent element oxide and niobium oxide is b, which satisfies a-b=4mol%-5mol%; The trivalent element comprises one or more of Y, Sm, Er, Sc and Nd. a and b satisfy a-b=4.3mol%-4.8mol%. 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 Y, 0.05wt%-1.21wt% of Nb and 0.1wt%-0.93wt% of Al.

2. The oxygen sensor of claim 1, wherein, The zirconia layer comprises, in terms of elements, 65.65wt%-67.12wt% of Zr, 5.91wt%-6.71wt% of Y, 0.06wt%-0.97wt% of Nb and 0.041wt%-0.75wt% of Al.

3. The oxygen sensor according to claim 1 or 2, wherein The phase of the zirconia layer comprises 97wt%-99wt% of tetragonal zirconia, and the rest is monoclinic zirconia.

4. The oxygen sensor of claim 3, wherein, The oxygen sensor is stacked with multiple layers of the substrate.

5. The oxygen sensor according to any one of claims 1 to 4, wherein 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.

6. The oxygen sensor according to any one of claims 1 to 5, wherein The heater is provided with a first insulating layer at both ends thereof facing the first substrate and the second substrate.

7. The oxygen sensor of claim 6, wherein A reference electrode is mounted in the second substrate and electrically connected to the first substrate and the third substrate, respectively.

8. The oxygen sensor of claim 7, wherein, 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.

9. The oxygen sensor of claim 7, wherein, The oxygen sensor is stacked with two layers of the substrate, which are a heating layer substrate and a detection layer substrate.

10. The oxygen sensor of claim 7, wherein, The raw materials are added to an organic additive for ball milling; 11. The oxygen sensor of claim 6, wherein, A binder is added for continuous ball milling to obtain a slurry; 12. The oxygen sensor according to any one of claims 1 to 11, wherein 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 on-off aging times of the substrate is greater than or equal to 8000, and the assembly yield of the substrate is greater than or equal to 80%.

13. A method of preparing a substrate for an oxygen sensor as claimed in any one of claims 1 to 12, wherein, The slurry is cast into a green body; An electrode is screen printed on the green body to prepare a green body; The green body is sintered to prepare the substrate; The raw materials comprise zirconia powder, niobium pentoxide powder, trivalent oxide powder and aluminum oxide powder. The trivalent oxide comprises one or more of yttrium oxide, samarium oxide, erbium oxide, scandium oxide and neodymium oxide. The trivalent oxide is yttrium oxide, and the total amount of yttrium oxide powder in the raw materials is X, which satisfies 7.5wt%-8.5wt%, and the total amount of zirconia powder and yttrium oxide powder is M, which satisfies 7wt% ​ ​ 14. The method of claim 13, wherein, ​ 15. The method of claim 14, wherein, The X and M satisfy 7.3wt%≤X-0.85M≤7.7wt%.

16. The method of claim 13, wherein, The alumina powder accounts for Z of the total amount of the raw materials, and satisfies 1≤M:Z≤3.

17. The method of claim 16, wherein, 1.5≤M:Z≤2.5.

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