Platinum-based alloy slurry for aluminum oxide co-firing and heating electrode

Abstract

The invention provides platinum-based alloy slurry for aluminum oxide co-firing and a heating electrode, the platinum-based alloy slurry for aluminum oxide co-firing comprises the following components in parts by weight: a) 65%-80% of a main conductive phase, the main conductive phase is monodisperse spherical platinum-palladium alloy powder, and the particle size range of the platinum-palladium alloy powder is 200-300 nm; the conductive material comprises the following components in percentage by weight: (a) 1%-5% of a conductive phase which is a metal organic compound, (b) 1%-5% of an auxiliary conductive phase which is a metal organic compound, (c) 0.5%-1% of a sintering aid which is gamma-Al2O3 powder or mixed powder of gamma-Al2O3 and alpha-Al2O3, and (d) 15%-30% of an organic carrier.

Description

Technical Field

[0001] The invention relates to the technical field of sensor heating electrodes, and in particular to a platinum-based alloy slurry for co-firing aluminum oxide and a heating electrode. Background Art

[0002] Platinum-based slurries have unique advantages in sensor manufacturing and high-temperature co-fired components HTCC electronic component applications. First, in terms of catalytic properties, platinum is a commonly used electrochemical catalytic functional phase, widely used in various gas detection and fuel cells, such as automobile exhaust nitrogen oxygen sensors. As a catalytic electrode material, it plays a decisive role in the response speed and sensitivity of the sensor, and is one of the most critical factors in determining the performance of nitrogen oxygen sensors. In addition, platinum has excellent high-temperature stability and corrosion resistance. On the one hand, platinum can withstand high-temperature sintering in an air atmosphere and still have a high electrical conductivity, so it has incomparable advantages in HTCC devices in an oxidizing atmosphere. On the other hand, platinum can resist the erosion of various corrosive substances and can still maintain stable performance in harsh environments such as high temperature, high pressure, and high humidity, providing a strong guarantee for the long-term stable operation of various sensors and extending the service life of the sensor. Therefore, it is widely used in the selection of heating electrode materials for nitrogen oxygen sensors. In terms of electrical properties, platinum in platinum-based slurries has excellent electrical conductivity and a stable temperature coefficient of resistance TCR, which can ensure accurate measurement and long-term stability of the current signal in the sensor.

[0003] However, there are many problems with the traditional platinum-based slurry when it is actually used in the heating electrode of automotive sensors. On the one hand, during the sintering process, platinum particles easily penetrate into the ceramic substrate, resulting in a loose structure of the conductive layer, reducing the density of the electrode, which not only affects the conductivity of the electrode, but also shortens the service life of the electrode, making it difficult to adapt to the long-term, high and low temperature repeated changes in the working requirements of the sensor. On the other hand, the electrode resistance temperature coefficient (TCR) made of the existing slurry is high, which makes the circuit control stability poor, and it is difficult to accurately control the circuit parameters when the temperature changes, resulting in sensor response delays and increased detection errors, limiting its application in high-precision exhaust gas component detection. In addition, due to the grain boundary effect, the resistance at the interface of the conductive layer particles is large. When subjected to voltage shock, the particle interface becomes the weak link of the entire circuit and is prone to damage, resulting in insufficient voltage resistance of the electrode, which cannot meet the requirements of complex working conditions such as high voltage shock when the car is powered on. Therefore, it is necessary to design a platinum-based alloy slurry and heating electrode for alumina co-firing to solve the above problems. Summary of the invention

[0004] The object of the present invention is to provide a platinum-based alloy slurry for alumina co-firing that can form a dense electrode layer, thereby achieving electrode requirements of low resistance, voltage shock resistance and long-term stability after sintering.

[0005] To achieve the above object, the present invention adopts the following technical solution: A platinum-based alloy paste for co-firing of alumina, which contains the following components in parts by weight: a) 65%-80% of the main conductive phase, the main conductive phase is monodisperse spherical platinum-palladium alloy powder, and the particle size range of the platinum-palladium alloy powder is 200-300 nm; b) 1%-5% of the auxiliary conductive phase, the auxiliary conductive phase is a metal organic compound; c) 0.5%-1% of the sintering aid, the sintering aid is γ-Al2O3 powder or a mixed powder of γ-Al2O3 and α-Al2O3; d) 15%-30% of the organic carrier.

[0006] As a further improved technical solution of the present invention, the platinum-palladium alloy powder is prepared by the following method: S1. Obtain platinum-palladium composite powder by the co-precipitation method: Dissolve chloroplatinic acid and chloropalladic acid in a solvent to form a mixed solution, add the mixed solution to an excessive reducing agent solution, the temperature of the reducing agent solution is 50-80 °C, stir until the reaction is complete, wash and dry to obtain the platinum-palladium composite powder, and the platinum-palladium composite powder includes platinum elemental powder and palladium elemental powder; S2. Heat-treat the platinum-palladium composite powder under a protective atmosphere to obtain platinum-palladium alloy powder: The protective atmosphere is nitrogen or argon, the heat treatment temperature is 400-600 °C, and the heat treatment time is 1-3 h.

[0007] As a further improved technical solution of the present invention, in step S1, the particle size range of the platinum-palladium composite powder is 20-50 nm, and the molar ratio of palladium to platinum in the platinum-palladium composite powder is 1:3-1:5.

[0008] As a further improved technical solution of the present invention, in step S1, in the mixed solution, the molar concentration of chloroplatinic acid is 3-5 times that of chloropalladic acid, the reducing agent is hydrazine hydrate, and the molar concentration of the reducing agent solution is 5-10 times the total molar concentration of chloroplatinic acid and chloropalladic acid.

[0009] As a further improved technical solution of the present invention, the particle size range of γ-Al2O3 is 3-20 nm, and the specific surface area is 50–300 m² / g.

[0010] As a further improved technical solution of the present invention, the added weight of α-Al2O3 is 0-10% of the added weight of γ-Al2O3, and the particle size range of α-Al2O3 is 3-20 nm. The combination of α-Al2O3 and γ-Al2O3 is convenient for adjusting the shrinkage rate matching with the green ceramic film, improving the co-firing matching and reliability.

[0011] As a further improved technical solution of the present invention, the organic carrier includes one or more of ethyl cellulose, acrylic resin, polycarbonate, epoxy resin, polyurethane resin, maleic anhydride resin, polystyrene, polyvinyl butyral or poly-α-methylstyrene resin, and a solvent.

[0012] As a further improved technical solution of the present invention, the solvent is one or more of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate, terpineol, turpentine, butyl carbitol, and dibutyl phthalate.

[0013] As a further improved technical solution of the present invention, the metal element in the metal organic compound is palladium or iridium, and the metal organic compound can be decomposed into metal elements at a temperature of 300-500°C.

[0014] The present invention also aims to provide an alumina co-fired heating electrode with a dense electrode layer, low resistance, high pressure shock resistance and high stability.

[0015] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: an alumina co-fired heating electrode, which is prepared by sintering the platinum-based alloy slurry for alumina co-fired as described in any of the above items on a green porcelain tape, and the sintering temperature and time are set in sequence: heating to 300°C and maintaining for 10-20min, 300-500°C and maintaining for 20-30min, 950-1050°C and maintaining for 20-30min, and 1300-1500°C and maintaining for 1-2h; the green porcelain tape is an alumina green porcelain tape or a green porcelain tape with an alumina system slurry printed on the surface, and the alumina system slurry is a type of functional slurry with alumina as the main component.

[0016] It can be seen from the above technical solutions that the platinum-based alloy slurry for alumina co-firing of the present invention has at least the following effects: (1) The platinum-based alloy paste of the present invention adds a thermally decomposable metal organic compound and γ-Al2O3 that can change its crystal form during sintering, and improves the electrode densification through precise coordination: in the initial stage of paste sintering, when the temperature reaches 300-500 °C, the metal organic compound begins to decompose and generates metal single particles. These metal single particles are distributed between the platinum-palladium alloy particles. As the temperature continues to rise, local alloying occurs between the metal single and the platinum-palladium alloy near the particle point contact, reducing the barrier for the sintering and growth of the platinum-palladium alloy particles themselves, and initially promoting the densification of the electrode layer; further, when the temperature rises to 950 °C, the high specific surface area γ-Al2O3 transforms into α-Al2O3 with a low specific surface area at high temperature, resulting in volume shrinkage. On the one hand, it adjusts the shrinkage rate matching between the paste and the alumina green ceramic film, and on the other hand, due to its stronger fluxing effect on metal particles with a high specific surface area, it reduces the penetration of metal single particles into the ceramic substrate, which is beneficial to the interconnection and densification of platinum-palladium alloy particles and metal single particles in the xy plane direction; γ-Al2O3 cooperates with the alloying process initiated by the previous metal organic compound to further improve the overall densification of the platinum heating electrode. (2) The platinum-based alloy paste of the present invention uses platinum-palladium alloy powder as the main conductive phase, which plays a role in reducing the TCR of the electrode throughout the process from paste forming to final use, optimizing the conductive performance and stabilizing the circuit control: by setting the ratio of platinum to palladium in the platinum-palladium alloy, the TCR of the electrode is significantly reduced from 3850 ppm of pure platinum to about 1500 ppm, effectively improving the stability of circuit control. During the operation of the sensor, even in the face of temperature changes, it can maintain stable resistance characteristics, extend the service life of the electrode, and meet the requirements of electronic devices such as automotive exhaust treatment sensors with high circuit stability requirements. (3) The platinum-based alloy paste of the present invention can synergistically enhance the voltage resistance of the circuit in stages: during the preparation process of the platinum-based alloy paste, a uniform platinum-palladium alloy powder is formed through coprecipitation of platinum-palladium composite powder and heat treatment under inert gas protection. On the one hand, it is beneficial to prevent the oxidation of metal palladium during sintering, and at the same time, the sintering and interconnection of platinum particles are densified, improving the stability of circuit control and the service life of the heating electrode; on the other hand, during sintering, the metal single generated by the decomposition of the metal organic compound further undergoes local alloying with the platinum-palladium alloy, changing the nature of the conductive phase at the particle interface, making the TCR of the interface lower than that of the platinum-palladium alloy. During the subsequent power-on heating process of the electrode, the resistance increase rate at the interface is lower than that of other parts, making the local voltage increase rate at the particle interface lower than the average value of the entire circuit. This characteristic effectively alleviates the shortcoming of the voltage-bearing capacity at the particle interface of the conductive layer, and synergistically improves the ability of the entire circuit to withstand voltage shocks in stages from the paste forming stage to the actual working process of the electrode, and can adapt to complex working conditions such as high voltage shocks during power-on. Description of the Drawings

[0017] Figure 1 SEM image of the electrode layer after sintering the paste in Comparative Example 4.

[0018] Figure 2 SEM image of the electrode layer after sintering the paste in Example 2. Detailed implementation manner

[0019] In order to make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0020] Prepare a platinum-based alloy paste A1 for co-firing alumina, which specifically includes the following steps: S1. Prepare a platinum-palladium composite powder by a co-precipitation method: Dissolve chloroplatinic acid and chloropalladic acid in a solvent to form a mixed solution, wherein the concentration of chloroplatinic acid is 0.08 M and the concentration of chloropalladic acid is 0.02 M; add the mixed solution to an excessive hydrazine hydrate solution within 15 minutes, and the concentration of the hydrazine hydrate solution is 1 M. The temperature of the hydrazine hydrate solution is 75 °C, keep warm and stir until the reaction is complete, wash the precipitate powder with deionized water 7-10 times, and dry to obtain a platinum-palladium composite powder with a particle size range of 30-50 nm (measure and statistically analyze the widest distance of multiple powder particles using a scanning electron microscope to obtain the powder particle size distribution, and the following particle size ranges are all obtained by this method). The platinum-palladium composite powder includes platinum elemental powder and palladium elemental powder, and the molar ratio of palladium to platinum is 1:4; S2. Prepare a platinum-palladium alloy powder by a heat treatment method: Perform heat treatment on the platinum-palladium composite powder under a protective atmosphere: The protective atmosphere is argon, the heat treatment temperature is 450 °C, and the heat treatment time is 2.5 h to obtain a monodisperse spherical platinum-palladium alloy powder with a particle size of 250-300 nm; through differential thermal-thermogravimetric analysis of this platinum-palladium alloy powder, it shows that no redox phenomenon occurs during the process from room temperature to 1500 degrees.

[0021] S3. Prepare an organic carrier: Accurately weigh 20 g of acrylic resin, 40 g of diethylene glycol butyl ether, and 40 g of diethylene glycol butyl ether acetate and add them to a container, place them in a constant temperature water bath at 80 °C for heat preservation, stir at 500 r / min, and keep warm for 1 h after complete dissolution to obtain an organic carrier for standby; S4. Mix the platinum-palladium alloy powder, iridium acetylacetonate, γ-Al2O3 powder (particle size 3-20 nm, specific surface area 50-300 m² / g (BET rapid method)), and the organic carrier according to the weight ratio in Table 1, homogenize through a homogenizer, and then transfer it to a three-roll grinder for grinding. The roller speed of the three-roll grinder is 100 r / min, the pressure is 3 MPa, roll 5 times, and finally perform decompression degassing. The decompression degassing pressure is -80 KPa to prepare a platinum-based alloy paste A1 for co-firing alumina. Example 2

[0022] Prepare the platinum-based alloy paste A2 for co-firing of alumina, which specifically includes the following steps: S1. It is generally the same as Example 1, except that the addition amounts of chloroplatinic acid and chloropalladic acid are changed so that the molar ratio of palladium to platinum in the platinum-palladium composite powder is 1:3; S2. It is the same as Example 1; S3. Prepare the organic carrier: Accurately weigh 20 g of polycarbonate, 40 g of diethylene glycol butyl ether, and 40 g of diethylene glycol ethyl ether acetate, add them to a container, place it in a constant temperature water bath at 80 °C for heat preservation, stir at 500 r / min, and keep it for 1 h after complete dissolution to obtain the organic carrier for standby; S4. Mix the platinum-palladium alloy powder, iridium acetylacetonate, γ-Al2O3 powder, and the organic carrier according to the weight ratios in Table 1, and perform homogenization, roll pressing, and vacuum deaeration by the same method as in Example 1 to prepare the platinum-based alloy paste A2 for co-firing of alumina. Example 3

[0023] Prepare the platinum-based alloy paste A3 for co-firing of alumina, which specifically includes the following steps: S1. It is generally the same as Example 1, except that the addition amounts of chloroplatinic acid and chloropalladic acid are changed so that the molar ratio of palladium to platinum in the platinum-palladium composite powder is 1:5; S2. It is the same as Example 1; S3. It is the same as Example 1; S4. Mix the platinum-palladium alloy powder, palladium acetylacetonate, γ-Al2O3 powder, and the organic carrier according to the weight ratios in Table 1, and perform homogenization, roll pressing, and vacuum deaeration by the same method as in Example 1 to prepare the platinum-based alloy paste A3 for co-firing of alumina. Example 4

[0024] Prepare the platinum-based alloy paste A4 for co-firing of alumina, which specifically includes the following steps: S1. It is the same as Example 2; S2. It is the same as Example 1; S3. It is the same as Example 2; S4. Mix the platinum-palladium alloy powder, iridium acetylacetonate, γ-Al2O3 powder, α-Al2O3 powder, and the organic carrier according to the weight ratios in Table 1, and perform homogenization, roll pressing, and vacuum deaeration by the same method as in Example 1 to prepare the platinum-based alloy paste A4 for co-firing of alumina. Example 5

[0025] Prepare the platinum-based alloy paste A5 for co-firing of alumina, which specifically includes the following steps: S1. It is the same as Example 2; S2. It is the same as Example 1; S3 is the same as in Example 2; S4. Mix platinum-palladium alloy powder, palladium acetylacetonate, γ-Al2O3 powder, α-Al2O3 powder and organic carrier according to the weight ratio in Table 1, and carry out homogenization, roll pressing and vacuum degassing by the same method as in Example 1 to obtain platinum-based alloy slurry A5 for co-firing with alumina. Comparative Example 1

[0026] Prepare platinum-based slurry B1, which specifically includes the following steps: S1. Directly select and purchase platinum elemental powder and palladium elemental powder for mixing. The molar ratio of palladium to platinum is 1:3, and the particle size range of palladium and platinum is 30-50 nm; S2. Prepare the organic carrier: the same as in Example 2; S3. Mix platinum-palladium mixed powder, palladium acetylacetonate, γ-Al2O3 powder and organic carrier according to the weight ratio in Table 1, and carry out homogenization, roll pressing and vacuum degassing by the same method as in Example 1 to obtain platinum-based slurry B1. Comparative Example 2

[0027] Prepare platinum-based slurry B2, which specifically includes the following steps: S1. The same as in Example 2; S2. The same as in Example 1; S3. The same as in Example 2; S4. Mix platinum-palladium alloy powder, γ-Al2O3 powder and organic carrier according to the weight ratio in Table 1, and carry out homogenization, roll pressing and vacuum degassing by the same method as in Example 1 to obtain platinum-based slurry B2. Comparative Example 3

[0028] Prepare platinum-based slurry B3, which specifically includes the following steps: S1. The same as in Example 2; S2. The same as in Example 1; S3. The same as in Example 2; S4. Mix platinum-palladium alloy powder, iridium acetylacetonate, α-Al2O3 powder and organic carrier according to the weight ratio in Table 1, and carry out homogenization, roll pressing and vacuum degassing by the same method as in Example 1 to obtain platinum-based slurry B3. Comparative Example 4

[0029] Prepare platinum-based slurry B4, which specifically includes the following steps: S1. The same as in Example 2; S2. The same as in Example 1; S3. The same as in Example 2; S4. Mix the platinum-palladium alloy powder, α-Al2O3 powder and organic carrier according to the weight ratios in Table 1, and perform homogenization, roll pressing and vacuum degassing by the same method as in Example 1 to obtain the platinum-based paste B4.

[0030] Table 1 Comparison table of parameter settings for examples and comparative examples

[0031] Perform performance tests on the pastes of Examples 1-5 and Comparative Examples 1-4: Prepare heating electrodes: Print lines with a length of 10 cm and a width of 0.1 cm on the alumina green tape substrate with the pastes prepared in Examples 1-5 and Comparative Examples 1-4 respectively, and then sinter at a gradient temperature: hold at 300°C for 15 min, 400°C for 20 min, 1000°C for 30 min, and 1450°C for 2 h.

[0032] Evaluate the sintering density and the matching degree with the alumina substrate: For the sintering density, observe the SEM photos of the electrode layer, and perform a score of 1-10 according to the observed pore conditions and flatness results. The evaluation results are shown in Table 2; for the matching degree with the alumina substrate, the present invention evaluates through the maximum warpage curvature after co-firing. The evaluation results are shown in Table 2.

[0033] TCR (temperature coefficient of resistance) test and calculation: Use an ohmmeter to test the resistance of the electrodes printed with the pastes prepared in Examples 1-5 and Comparative Examples 1-4 at 25°C and 125°C respectively, record and calculate the temperature coefficient of resistance. The calculation results are shown in Table 2.

[0034] Withstand voltage test: Evaluate using the multiple of the input voltage / rated voltage, that is, under the same conditions, compare the maximum applied voltage that the platinum heating circuit can withstand within 5 s. The comparison results are shown in Table 2.

[0035] Table 2 Comparison table of performance parameters of heating electrodes

[0036] Example analysis In terms of density and matching degree with the alumina substrate: As can be seen from Table 1 and Table 2, metal-organic compounds that can be thermally decomposed (iridium acetylacetonate or palladium acetylacetonate) and γ-Al2O3 were added in Examples 1-5. In the initial stage of sintering, the metal-organic compounds decomposed to generate metal single-particle grains, promoting the initial densification of the electrode layer. When the temperature rose to a high temperature, the volume shrinkage caused by the crystal form transformation of γ-Al2O3 adjusted the shrinkage rate matching with the green alumina ceramic film. Moreover, due to the fluxing effect of the high specific surface area on the metal grains, the penetration of metal single-particle grains into the ceramic substrate was reduced. Synergistic with the previous alloying process, the sintering density of the examples all reached about 9.0 points, higher than about 8.0 points of the comparative examples, improving the overall density of the electrodes. Please refer to Figure 2 As shown in the SEM image of the heating electrode prepared from Slurry A2 in Example 2, no pores were observed, and the surface flatness was relatively high, with the best density. Figure 1 The SEM image of the heating electrode prepared from Slurry B4 in Comparative Example 4 is shown. The porosity is relatively high, the surface is rough, and some particles are in a discrete state. For the matching degree with the alumina substrate, the maximum warpage curvature of Examples 1-5 is between 0.11% and 0.15%, indicating that with the cooperation of the main conductive phase, auxiliary conductive phase, and sintering aids in the alloying process, the slurry has a good matching degree with the alumina substrate.

[0037] In terms of TCR: Using platinum-palladium alloy powder as the main conductive phase, by setting different platinum-palladium molar ratios, the TCR of the electrode was effectively reduced. For example, the TCR of Examples 1-5 was 1520-1723 ppm / °C, much lower than 2210 ppm / °C of Comparative Example 1, 2285 ppm / °C of Comparative Example 2, etc. In Example 2, the 1:3 palladium-platinum molar ratio made the degree of electron delocalization higher and the lattice structure more regular, with the lowest TCR. Optimizing the conductive performance throughout the process from slurry forming to final use, stabilizing the circuit control, and meeting the requirements of equipment with high requirements for circuit stability.

[0038] In terms of the withstand voltage ability: The input voltage / rated voltage of Examples 1-5 was between 1.8 and 2.2, and Example 2 was the best. During the preparation process of Examples 1-5, uniform platinum-palladium alloy powder was formed through coprecipitated platinum-palladium composite powder combined with an inert gas protection heat treatment process, preventing the oxidation of palladium metal and making the platinum grains sinter and interconnect densely. At the same time, the metal single particles generated by the decomposition of the metal-organic compounds were locally alloyed with the platinum-palladium alloy, changing the properties of the conductive phase at the particle interface, reducing the TCR at the interface, and making the resistance increase rate at the interface slower when energized and heated, and the local voltage increase rate lower than the circuit average value, alleviating the short board of the voltage borne at the particle interface of the conductive layer. Analysis of Comparative Examples

[0039] Comparative Example 1: Compared with Example 1, the molar ratio of the main conductive phase platinum and palladium is the same, the auxiliary conductive phase and other components are the same, but in Comparative Example 1, a mixture of platinum elemental powder and palladium elemental powder is directly used without alloying treatment, forming an uneven phase structure that interferes with electron conduction. The room temperature resistance reaches 26.8 Ω, the TCR is 2210 ppm / °C, and both the sintering densification and the matching degree with the alumina substrate are lower than those of Example 1; however, compared with the pure platinum paste, the TCR of Comparative Example 1 has a significant reduction.

[0040] Comparative Example 2: The proportion of the main conductive phase is the same as that in Example 2, but there is no auxiliary conductive phase, resulting in worse performance in terms of resistance, TCR, sintering densification, and matching degree with the alumina substrate than Example 2, indicating the important role of the auxiliary conductive phase in optimizing the electrode performance.

[0041] Comparative Example 3: Compared with Example 2, the sintering aid lacks γ-Al2O3. There are differences in its resistance, TCR and other properties from those of Example 2, indicating that γ-Al2O3 is superior to α-Al2O3 in improving electrode performance (such as densification and matching with the alumina substrate).

[0042] Comparative Example 4: Without an auxiliary conductive phase and lacking γ-Al2O3 as a sintering aid, its various performance parameters such as resistance (34.1 Ω), TCR (2151 ppm / °C), sintering densification (7.5 points), matching degree with the alumina substrate (0.28%), and voltage resistance ability are all poor, further illustrating the importance of the synergistic effect of multiple components in improving the electrode performance in the present invention.

[0043] The above embodiments are only used to illustrate the present invention and do not limit the technical solutions described in the present invention. The understanding of this specification should be based on those skilled in the art of the relevant technical field. Although this specification has described the present invention in detail with reference to the above embodiments, those of ordinary skill in the art should understand that those skilled in the relevant technical field can still modify the present invention or make equivalent substitutions, and all technical solutions and their improvements that do not depart from the spirit and scope of the present invention should be covered within the scope of the claims of the present invention.

Claims

1. A platinum-based alloy paste for co-firing of alumina, characterized in that: Contains the following components in parts by weight: a) 65%-80% of a main conductive phase, wherein the main conductive phase is a monodisperse spherical platinum-palladium alloy powder, and the particle size of the platinum-palladium alloy powder is in the range of 200-300 nm; b) 1%-5% auxiliary conductive phase, wherein the auxiliary conductive phase is a metal organic compound; c) 0.5%-1% sintering aid, wherein the sintering aid is γ-Al2O3 powder or a mixed powder of γ-Al2O3 and α-Al2O3; d) 15%-30% organic carrier.

2. The platinum-based alloy paste for co-firing alumina according to claim 1, wherein: The platinum-palladium alloy powder is prepared by the following method: S1. Obtaining platinum-palladium composite powder by a coprecipitation method: dissolving chloroplatinic acid and chloropalladic acid in a solvent to form a mixed solution, adding the mixed solution to an excess reducing agent solution at a temperature of 50-80° C., stirring until the reaction is complete, washing, and drying to obtain a platinum-palladium composite powder, wherein the platinum-palladium composite powder includes a platinum elemental powder and a palladium elemental powder; S2. Heat-treating the platinum-palladium composite powder under a protective atmosphere to obtain platinum-palladium alloy powder: the protective atmosphere is nitrogen or argon, the heat treatment temperature is 400-600° C., and the heat treatment time is 1-3 hours.

3. The platinum-based alloy paste for co-firing alumina according to claim 2, wherein: In step S1, the particle size range of the platinum-palladium composite powder is 20-50 nm, and the molar ratio of palladium to platinum in the platinum-palladium composite powder is 1:3-1:

5.

4. The platinum-based alloy paste for co-firing of alumina according to claim 2, characterized in that: In step S1, in the mixed solution, the molar concentration of chloroplatinic acid is 3-5 times the molar concentration of chloropalladic acid, the reducing agent is hydrazine hydrate, and the molar concentration of the reducing agent solution is 5-10 times the total molar concentration of chloroplatinic acid and chloropalladic acid.

5. The platinum-based alloy paste for co-firing alumina according to claim 1, characterized in that: The particle size of γ-Al2O3 ranges from 3-20nm and the specific surface area is 50–300 m² / g.

6. The platinum-based alloy paste for co-firing of alumina according to claim 1, characterized in that: The added weight of α-Al2O3 is 0-10% of the added weight of γ-Al2O3, and the particle size range of α-Al2O3 is 3-20nm.

7. The platinum-based alloy paste for co-firing alumina according to claim 1, characterized in that: The organic carrier includes one or more of ethyl cellulose, acrylic resin, polycarbonate, epoxy resin, polyurethane resin, maleic anhydride resin, polystyrene, polyvinyl butyral or poly-α-methylstyrene resin, and a solvent.

8. The platinum-based alloy paste for co-firing of alumina according to claim 7, characterized in that: The solvent is one or more of diethylene glycol butyl ether, diethylene glycol butyl ether acetate, diethylene glycol ethyl ether acetate terpineol, turpentine, butyl carbitol, and dibutyl phthalate.

9. The platinum-based alloy paste for co-firing alumina according to claim 1, wherein: The metal element in the metal organic compound is palladium or iridium, and the metal organic compound can be decomposed into metal elements at a temperature of 300-500°C.

10. An alumina co-fired heating electrode, characterized in that: The green porcelain tape is prepared by sintering the platinum-based alloy slurry for co-firing alumina as described in any one of claims 1 to 9 on a green porcelain tape, and the sintering temperature and time are set to: heating to 300°C and maintaining for 10-20min, 300-500°C and maintaining for 20-30min, 950-1050°C and maintaining for 20-30min, and 1300-1500°C and maintaining for 1-2h; the green porcelain tape is an alumina green porcelain tape or a green porcelain tape with an alumina system slurry printed on the surface.

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