A method for pre-synthesizing ruthenium-based conductive phases in stages and applications thereof

Abstract

The application discloses a method for pre-synthesizing a ruthenium-based conductive phase in stages and application, and relates to the technical field of electronic functional materials and thick film resistance. The method for pre-synthesizing the ruthenium-based conductive phase in stages comprises the following steps: mixing the ruthenium-based conductive phase and rare earth oxides to obtain mixed raw materials; and performing a pre-synthetic heat treatment on the mixed raw materials to obtain a pre-synthetic conductive phase. In order to study the application effect of the pre-synthetic conductive phase prepared by the application in the preparation of a PTC thermistor film, the pre-synthetic conductive phase is used to prepare the PTC thermistor film, and the specific steps are as follows: mixing the pre-synthetic conductive phase with glass powder, auxiliary oxides and an organic carrier, and then rolling to obtain PTC thermistor paste; and the PTC thermistor film can be prepared subsequently; under the same paste preparation and sintering conditions, the PTC thermistor paste prepared by the method has significantly improved consistency of sheet resistance and resistance temperature coefficient. The application has clear process structure and good repeatability, and is suitable for the preparation of a ruthenium-based PTC thermistor paste.

Description

Technical Field

[0001] This invention relates to a method and application of staged pre-synthesis of ruthenium-based conductive phases, belonging to the field of electronic functional materials and thick film resistors. Background Technology

[0002] Ruthenium-based PTC thermistors are widely used in temperature detection, circuit protection, and temperature compensation due to their positive temperature coefficient of resistance. Ruthenium-based PTC resistors fabricated using thick-film screen printing technology offer advantages such as mature technology and a wide resistance range.

[0003] In related technologies, to improve electrical performance, modifications are typically made by adjusting the composition of the conductive phase or introducing doping components. Some technical solutions also propose pre-synthesizing the conductive phase to improve compositional uniformity. However, existing pre-synthesizing methods mostly employ a single-stage high-temperature heat treatment structure, lacking staged control over the formation process of the conductive phase interface.

[0004] In actual pulping and sintering processes, slurries obtained from single-stage pre-synthesis treatment may still exhibit issues such as sheet resistance fluctuations, insufficient consistency in temperature coefficient of resistance, and decreased stability during repeated sintering. Therefore, it is necessary to provide a new pre-synthesis process structure that allows for more controllable adjustment of the conductive phase interface state through staged heat treatment, thereby improving the electrical performance stability of ruthenium-based PTC thermistor slurries. Summary of the Invention

[0005] To address the shortcomings of related technologies, this invention provides a method and application for the phased pre-synthesis of ruthenium-based conductive phases, which realizes the design of the interface state of the conductive phase in the resistive slurry and solves the problems of sheet resistance fluctuation, insufficient uniformity of temperature coefficient of resistance, and decreased stability of repeated sintering in existing slurries.

[0006] One objective of this invention is to provide a method for the phased pre-synthesis of ruthenium-based conductive phases, specifically comprising the following steps: (1) Mix the ruthenium-based conductive phase with rare earth trioxide to obtain a mixed raw material.

[0007] (2) The mixed raw materials are subjected to staged pre-synthetic heat treatment to obtain a pre-synthetic conductive phase.

[0008] Preferably, in step (1), the ruthenium-based conductive phase is RuO2; the rare earth trioxide is Nd2O3; and the ruthenium-based conductive phase and the rare earth trioxide are mixed in a mass ratio of 100:(1~5) of ruthenium-based conductive phase to rare earth trioxide.

[0009] Preferably, step (2) of the phased pre-synthesis heat treatment includes a first stage of low-temperature activation treatment and a second stage of high-temperature pre-synthesis treatment. The conditions for the first stage of low-temperature activation treatment are: heating to 400-600℃ at a heating rate of 3-10℃ / min and holding for 0.5-2h; the conditions for the second stage of high-temperature pre-synthesis treatment are: heating to 650-850℃ at a heating rate of 5-15℃ / min and holding for 0.5-3h.

[0010] More preferably, the staged pre-synthesis heat treatment in step (2) is carried out in an air atmosphere; the low-temperature activation treatment temperature of the first stage is 450~550℃; and the high-temperature pre-synthesis treatment temperature of the second stage is 700~800℃.

[0011] Another objective of this invention is to provide an application of a staged pre-synthesized ruthenium-based conductive phase in the preparation of PTC thermistor films, specifically including the following steps: (1) The pre-synthesized conductive phase is mixed with glass powder and auxiliary oxide to form a solid phase. The solid phase is then mixed with an organic carrier and rolled to prepare a PTC thermistor slurry.

[0012] (2) The PTC thermistor paste is screen printed and sintered to obtain a PTC thermistor film.

[0013] Preferably, the glass powder in step (1) comprises, by mass percentage: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3.

[0014] Preferably, the glass powder preparation method in step (1) is as follows: weigh the glass powder raw material according to the proportion, then heat and melt the glass powder raw material at 1200℃ to obtain molten glass, quench the molten glass, crush it, ball mill it, sieve it and dry it to obtain glass powder.

[0015] Preferably, the organic carrier in step (1) is composed of an organic solvent, a binder, a thixotropic agent, a surfactant, and a coupling agent, wherein the organic solvent is one or more of terpineol, dodecayl alcohol ester, and diethylene glycol butyl ether acetate; the binder is ethyl cellulose; the thixotropic agent is one or more of polyamide wax, fumed silica, and hydrogenated castor oil; and the surfactant is one or more of Span 85, Span 80, and lecithin. The composition of the organic carrier, by mass percentage, includes 85% organic solvent, 10% binder, 2% thixotropic agent, 1% surfactant, and 2% coupling agent. The rolling conditions are: using a three-roll milling method, milling 2-3 times, with the milling gap gradually reduced to 5-10µm.

[0016] More preferably, in step (1), the organic solvent is terpineol; the thixotropic agent is polyamide wax; the surfactant is Span 85; and the coupling agent is KH570 silane coupling agent.

[0017] Preferably, in step (1), based on the total mass of the PTC thermistor slurry as 100%, the content of the pre-synthesized conductive phase in the PTC thermistor slurry is 40-60% by mass percentage, the content of glass powder is 20-40% by mass percentage, the content of organic carrier is 20-45% by mass percentage, and the content of auxiliary oxide is 1-5% by mass percentage.

[0018] Preferably, the auxiliary oxides in step (1) are copper oxide and vanadium pentoxide.

[0019] More preferably, in step (1), copper oxide and vanadium pentoxide are mixed in a mass ratio of 4:1 to form an auxiliary oxide.

[0020] Preferably, the conditions for screen printing and sintering in step (2) are as follows: PTC thermistor paste is printed on an alumina ceramic substrate to form a paste layer with a thickness of 10 μm. The alumina ceramic substrate is then dried, and then heated to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After cooling, a PTC thermistor film is obtained.

[0021] The pattern printed on the PTC thermistor paste of this invention is as follows: Figure 1 As shown.

[0022] Mechanism of the invention: This invention employs a staged pre-synthesis process. At a low temperature, it promotes the adsorption and initial diffusion of rare earth oxides on the surface of RuO2 particles, while at a high temperature, it further forms a stable interface structure, thereby regulating the contact state and electron transport paths between conductive phase particles. Compared to a single-stage pre-synthesis method, this approach effectively improves the continuity and uniformity of the conductive network, enhancing the stability of electrical properties.

[0023] The beneficial effects of this invention are: (1) The state of the conductive phase interface can be controlled by a phased pre-synthesis process.

[0024] (2) Effectively reduce sheet resistance fluctuations and improve TCR consistency.

[0025] (3) Improve the stability and repeatability of slurry reburning.

[0026] (4) Improve the quality of resistive film forming and reduce crack defects.

[0027] (5) The process is simple and suitable for industrial preparation. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the printing pattern of the PTC thermistor paste of the present invention.

[0029] Figure 2 The TCR data graphs are of the PTC thermistor pastes prepared in Examples 1-4 and Comparative Examples 1-3 of this invention.

[0030] Figure 3 The diagram shows the sheet resistance data of the PTC thermistor paste prepared in Examples 1-4 and Comparative Examples 1-3 of this invention.

[0031] Figure 4 This is a surface morphology diagram of the PTC thermistor film prepared in Example 3 of the present invention.

[0032] Figure 5 This is a surface morphology diagram of the PTC thermistor film prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0033] To better illustrate the purpose, technical solution, and advantages of this invention, the invention will be further described below with reference to specific embodiments. In the embodiments and comparative examples of this invention, unless otherwise specified, all chemical reagents used were commercially available analytical grade reagents.

[0034] Example 1 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0035] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 500℃ at a heating rate of 8℃ / min and held for 1h; the second stage (high temperature pre-synthesis): the temperature was raised to 750℃ at a heating rate of 8℃ / min and held for 1h; a pre-synthesized conductive phase was obtained.

[0036] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of copper oxide CuO and vanadium pentoxide V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of the following mass percentage composition: 85% terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground twice to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0037] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0038] The sheet resistance of the PTC thermistor paste prepared according to the international standard 17473-3-2008 was tested. The specific method was as follows: the electrodes of the resistance measuring instrument were placed in the electrode area of ​​the sample to be tested, ensuring good contact. Measurements were taken three times at each measurement point, and the average value was calculated. The formula for calculating the sheet resistance test result is as follows: Rs = R / 100; In the formula: Rs is the resistance value per square meter (Ω / □); R is the resistance value per 100 square meter (Ω).

[0039] Temperature Coefficient of Resistance (TCR) Test: A certain length of wire is welded to the electrode area of ​​the PTC thermistor paste sample to be tested. The sample is placed on a heating stage, and the other end of the wire is connected to a resistance tester. The test temperature is 25℃-125℃. The formula for calculating the temperature coefficient of resistance is as follows: ; In the formula: R1 is the resistance at temperature T1, in ohms (Ω); R2 is the resistance at temperature T2, in ohms (Ω); T1 is the test temperature T1, in °C; T2 is the test temperature T2, in °C.

[0040] Tests showed that the PTC thermistor paste prepared in this embodiment has a resistance of 2Ω / □ below 25°C (see [reference]). Figure 3 The TCR value is 4030 ppm / ℃ (see Figure 2 The linear change rate was 0.99, and the reheat change rate was 1.6%. The test results show that the slurry obtained in this embodiment has stable positive temperature coefficient characteristics and good electrical performance consistency after sintering. The PTC thermistor film prepared in this embodiment has a relatively complete surface morphology and no obvious cracks were observed.

[0041] Example 2 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0042] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 450℃ at a heating rate of 8℃ / min and held for 1h; the second stage (high temperature pre-synthesis): the temperature was raised to 700℃ at a heating rate of 8℃ / min and held for 1h; a pre-synthesized conductive phase was obtained.

[0043] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground three times to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0044] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0045] The sheet resistance and TCR of the PTC thermistor paste prepared in this embodiment were tested using the same testing method as in Example 1. The test results showed that the sheet resistance of the PTC thermistor paste prepared in this embodiment was 1.5 Ω / □ at 25°C (see Example 1). Figure 3 The TCR value is 4330 ppm / ℃ (see Figure 2 The linear change rate was 0.99, and the reheat change rate was 1.3%. The test results show that the slurry obtained in this embodiment has stable positive temperature coefficient characteristics and good electrical performance consistency after sintering. The PTC thermistor film prepared in this embodiment has a relatively complete surface morphology and no obvious cracks were observed.

[0046] Example 3 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0047] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 550℃ at a heating rate of 8℃ / min and held for 1h; the second stage (high temperature pre-synthesis): the temperature was raised to 750℃ at a heating rate of 8℃ / min and held for 1h; a pre-synthesized conductive phase was obtained.

[0048] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground twice to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0049] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0050] The sheet resistance and TCR of the PTC thermistor paste prepared in this embodiment were tested using the same testing method as in Example 1. The test results showed that the sheet resistance of the PTC thermistor paste prepared in this embodiment was 1 Ω / □ at 25°C (see Example 1). Figure 3 The TCR value was 4620 ppm / ℃ (see [reference]). Figure 2 The linear change rate was 0.99, and the reheat change rate was 1.1%. The test results show that the slurry obtained in this embodiment has a stable positive temperature coefficient and good electrical performance consistency after sintering. To further illustrate the effect of the technical solution of this invention, the morphology of the PTC thermistor film prepared in Example 3 was observed, as shown... Figure 4 As shown, the PTC thermistor film prepared in Example 3 has a relatively complete surface morphology and no obvious cracks were observed.

[0051] Example 4 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0052] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 500℃ at a heating rate of 8℃ / min and held for 1h; the second stage (high temperature pre-synthesis): the temperature was raised to 800℃ at a heating rate of 8℃ / min and held for 1h; a pre-synthesized conductive phase was obtained.

[0053] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground twice to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0054] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0055] The sheet resistance and TCR of the PTC thermistor paste prepared in this embodiment were tested using the same testing method as in Example 1. The test results showed that the sheet resistance of the PTC thermistor paste prepared in this embodiment was 0.9 Ω / □ at 25°C (see Example 1). Figure 3 The TCR value is 4755 ppm / ℃ (see Figure 2 The linear change rate was 0.99, and the reheat change rate was 0.9%. The test results show that the slurry obtained in this embodiment has stable positive temperature coefficient characteristics and good electrical performance consistency after sintering. The PTC thermistor film prepared in this embodiment has a relatively complete surface morphology and no obvious cracks were observed.

[0056] Example 5 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:5 to obtain mixed raw materials.

[0057] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 600℃ at a heating rate of 3℃ / min and held for 0.5h; the second stage (high temperature pre-synthesis): the temperature was raised to 650℃ at a heating rate of 5℃ / min and held for 3h; a pre-synthesized conductive phase was obtained.

[0058] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground three times to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 40% pre-synthesized conductive phase by mass, 30% glass powder by mass, 29% organic carrier by mass, and 1% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0059] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0060] The sheet resistance and TCR of the PTC thermistor paste prepared in this embodiment were tested using the same testing method as in Example 1. The results showed that the sheet resistance of the PTC thermistor paste prepared in this embodiment was 1.8 Ω / □ at 25°C, the TCR value was 3830 ppm / °C, the linear change rate was 0.98, and the reheat change rate was 1.4%. The test results indicate that the paste obtained in this embodiment exhibits stable positive temperature coefficient characteristics and good electrical performance consistency after sintering. The surface morphology of the PTC thermistor film prepared in this embodiment was relatively intact, and no obvious cracks were observed.

[0061] Example 6 A method for pre-synthesizing ruthenium-based conductive phases in stages includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:3 to obtain mixed raw materials.

[0062] (2) The mixed raw materials were subjected to staged pre-synthesis heat treatment in air atmosphere. The first stage (low temperature activation): the temperature was raised to 400℃ at a heating rate of 10℃ / min and held for 2h; the second stage (high temperature pre-synthesis): the temperature was raised to 850℃ at a heating rate of 15℃ / min and held for 0.5h; a pre-synthesized conductive phase was obtained.

[0063] To investigate the application effect of the pre-synthesized conductive phase prepared in this embodiment in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this embodiment, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground three times to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 22% organic carrier by mass, and 3% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0064] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0065] The sheet resistance and TCR of the PTC thermistor paste prepared in this embodiment were tested using the same testing method as in Example 1. The results showed that the sheet resistance of the PTC thermistor paste prepared in this embodiment was 1.2 Ω / □ at 25°C, the TCR value was 4263 ppm / °C, the linear change rate was 0.98, and the reheat change rate was 1.7%. The test results indicate that the paste obtained in this embodiment exhibits stable positive temperature coefficient characteristics and good electrical performance consistency after sintering. The surface morphology of the PTC thermistor film prepared in this embodiment was relatively intact, and no obvious cracks were observed.

[0066] Comparative Example 1 A method for preparing a PTC thermistor film specifically includes the following steps: (1) RuO2 and Nd2O3 are mixed in a mass ratio of 100:1 to obtain a conductive phase; glass powder raw materials are weighed according to the composition of glass powder by mass percentage, including: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw materials are then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder; the conductive phase is mixed with glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and organic carrier (which has The organic carrier is composed of the following components by mass percentage: 85% terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent. The mixture is then ground using a three-roll mill, with the grinding gap gradually reduced to 5-10 µm, and the mixture is ground twice to ensure thorough dispersion of the components, thus preparing a PTC thermistor slurry. The PTC thermistor slurry contains 55% pre-synthesized conductive phase, 20% glass powder, 20% organic carrier, and 5% auxiliary oxide (composed of CuO and V2O5 mixed in a mass ratio of 4:1).

[0067] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0068] The sheet resistance and TCR of the PTC thermistor paste prepared in this comparative example were tested using the same testing method as in Example 1. The results showed that the sheet resistance of the PTC thermistor paste prepared in this comparative example was 3 Ω / □ at 25°C, the TCR value was 2500 ppm / °C, the linear change rate was 0.83, and the reheat change rate was 3%. The test results indicate that because this comparative example did not undergo a staged pre-synthesis treatment of the conductive phase, the electrical properties of the resulting paste fluctuated significantly after sintering, the positive temperature coefficient characteristics were unstable, and the spreadability of the paste was out of control during printing, leading to a decrease in the quality of the resistive film formation and the stability of its electrical properties. The morphology of the PTC thermistor film prepared in Comparative Example 1 was observed, as shown below. Figure 5As shown, the PTC thermistor film prepared in Comparative Example 1 showed obvious cracks in the film layer after sintering.

[0069] Comparative Example 2 A method for pre-synthesizing a ruthenium-based conductive phase specifically includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0070] (2) The mixed raw materials were subjected to pre-synthetic heat treatment in air atmosphere, under the following conditions: heating to 500℃ at a heating rate of 8℃ / min and holding for 1h to obtain the pre-synthesized conductive phase.

[0071] To investigate the application effect of the pre-synthesized conductive phase obtained in this comparative example in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this comparative example, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground twice to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0072] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0073] The sheet resistance and TCR of the PTC thermistor paste prepared in this comparative example were tested using the same testing method as in Example 1. The results showed that the sheet resistance of the PTC thermistor paste prepared in this comparative example was 2.9 Ω / □ at 25°C, the TCR value was 2589 ppm / °C, the linear change rate was 0.85, and the reheat change rate was 2.8%. The test results indicate that when the pre-synthesized material only undergoes low-temperature activation heat treatment, the electrical stability of the resulting paste decreases. This is because the solid-phase reaction between RuO2 and Nd2O3 is insufficient under low-temperature conditions, leading to insufficient formation of the pre-synthesized conductive phase, which is detrimental to the formation of a stable conductive network.

[0074] Comparative Example 3 A method for pre-synthesizing a ruthenium-based conductive phase specifically includes the following steps: (1) Mix RuO2 and Nd2O3 in a mass ratio of 100:1 to obtain mixed raw materials.

[0075] (2) The mixed raw materials were subjected to pre-synthetic heat treatment in air atmosphere, under the following conditions: heating to 750℃ at a heating rate of 8℃ / min and holding for 1h to obtain the pre-synthesized conductive phase.

[0076] To investigate the application effect of the pre-synthesized conductive phase obtained in this comparative example in the preparation of PTC thermistor films, a PTC thermistor film was prepared using the pre-synthesized conductive phase of this comparative example, specifically including the following steps: (1) The glass powder raw material is weighed according to the following mass percentage composition: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3. The glass powder raw material is then heated and melted at 1200℃ to obtain molten glass. The molten glass is quenched, crushed, ball-milled for 12 hours, passed through a 400-mesh sieve to collect the sieve material, and dried in an air atmosphere to obtain glass powder. The pre-synthesized conductive phase is mixed with the glass powder and auxiliary oxide (which consists of CuO and V2O5) to form a solid phase. The solid phase and the organic carrier (which consists of 85% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3) are then mixed. Terpineol, 10% ethyl cellulose, 2% polyamide wax, 1% Span 85, and 2% KH570 silane coupling agent were mixed and then ground using a three-roll mill. The grinding gap was gradually reduced to 5-10 µm, and the mixture was ground twice to ensure that the components were fully dispersed. This yielded a PTC thermistor slurry. The PTC thermistor slurry contained 55% pre-synthesized conductive phase by mass, 20% glass powder by mass, 20% organic carrier by mass, and 5% auxiliary oxide by mass (the auxiliary oxide consisted of CuO and V2O5 mixed in a mass ratio of 4:1).

[0077] (2) The PTC thermistor paste was printed on the alumina ceramic substrate with the electrodes brushed on using a thick film screen printing process. The thickness of the PTC thermistor paste on the alumina ceramic substrate was 10 μm. Then the alumina ceramic substrate was placed in a drying oven to dry, and then placed in a sintering furnace to heat to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After that, it was cooled to room temperature with the furnace to prepare the PTC thermistor film.

[0078] The sheet resistance and TCR of the PTC thermistor paste prepared in this comparative example were tested using the same testing method as in Example 1. The test results showed that the sheet resistance of the PTC thermistor paste prepared in this comparative example was 2.7 Ω / □ at 25°C (see Example 1). Figure 3 The TCR value was 2633 ppm / ℃ (see [reference]). Figure 2 The linear change rate was 0.88, and the reheat change rate was 2.6%. The test results show that when the pre-synthesis only undergoes high-temperature pre-synthesis heat treatment, the electrical properties of the resulting slurry are inconsistent. This is because excessively high temperatures cause the pre-synthesized products to grow grains or agglomerate, which reduces the uniformity of the conductive phase dispersion.

[0079] The PTC thermistor paste prepared in this embodiment of the invention, after pre-synthesis treatment with rare earth oxides participating in the conductive phase, exhibits a good linear relationship between sheet resistance and temperature coefficient of resistance, with a linear correlation coefficient R0. 2 The result shows that the pre-synthesis treatment method described in this invention can effectively improve the consistency and repeatability of the electrical properties of PTC thermistor slurry, making it more suitable for practical application needs.

[0080] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A method for staged pre-synthesis of ruthenium-based conductive phases, characterized in that, Specifically, the following steps are included: (1) The ruthenium-based conductive phase is mixed with rare earth trioxides to obtain a mixed raw material; (2) The mixed raw materials are subjected to staged pre-synthetic heat treatment to obtain a pre-synthetic conductive phase.

2. The method for staged pre-synthesis of ruthenium-based conductive phase according to claim 1, characterized in that, In step (1), the ruthenium-based conductive phase is RuO2; the rare earth trioxide is Nd2O3; the ruthenium-based conductive phase and the rare earth trioxide are mixed in a mass ratio of 100:(1~5) of ruthenium-based conductive phase to rare earth trioxide.

3. The method for staged pre-synthesis of ruthenium-based conductive phases according to claim 1, characterized in that, The step (2) pre-synthesis heat treatment includes a first stage of low-temperature activation treatment and a second stage of high-temperature pre-synthesis treatment. The first stage of low-temperature activation treatment is performed by heating to 400-600℃ at a heating rate of 3-10℃ / min and holding for 0.5-2h. The second stage of high-temperature pre-synthesis treatment is performed by heating to 650-850℃ at a heating rate of 5-15℃ / min and holding for 0.5-3h.

4. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 1 in the preparation of PTC thermistor films specifically includes the following steps: (1) The pre-synthesized conductive phase is mixed with glass powder and auxiliary oxide to form a solid phase. The solid phase is then mixed with an organic carrier and rolled to prepare a PTC thermistor slurry. (2) The PTC thermistor paste is screen printed and sintered to obtain a PTC thermistor film.

5. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, The glass powder in step (1) comprises, by mass percentage: 10% CaO, 18% Al2O3, 18% SiO2, 34% B2O3, 10% BaO, 5% Na2O, 3% Li2O, and 2% Bi2O3.

6. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, The preparation method of glass powder in step (1) is as follows: weigh the glass powder raw material according to the proportion, then heat and melt the glass powder raw material at 1200℃ to obtain molten glass, quench the molten glass, crush it, ball mill it, sieve it and dry it to obtain glass powder.

7. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, The organic carrier in step (1) is composed of an organic solvent, a binder, a thixotropic agent, a surfactant, and a coupling agent. The organic solvent is one or more of terpineol, dodecayl alcohol ester, and diethylene glycol butyl ether acetate; the binder is ethyl cellulose; the thixotropic agent is one or more of polyamide wax, fumed silica, and hydrogenated castor oil; and the surfactant is one or more of Span 85, Span 80, and lecithin. The composition of the organic carrier, by mass percentage, includes 85% organic solvent, 10% binder, 2% thixotropic agent, 1% surfactant, and 2% coupling agent. The rolling conditions are as follows: a three-roll milling method is used, milling 2-3 times, with the milling gap gradually reduced to 5-10µm.

8. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, In step (1), based on the total mass of the PTC thermistor slurry as 100%, the content of the pre-synthesized conductive phase in the PTC thermistor slurry is 40-60% by mass percentage, the content of glass powder is 20-40% by mass percentage, the content of organic carrier is 20-45% by mass percentage, and the content of auxiliary oxide is 1-5% by mass percentage.

9. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, The auxiliary oxides in step (1) are copper oxide and vanadium pentoxide.

10. The application of the staged pre-synthesized ruthenium-based conductive phase according to claim 4 in the preparation of PTC thermistor films, characterized in that, The conditions for screen printing and sintering in step (2) are as follows: PTC thermistor paste is printed on an alumina ceramic substrate to form a paste layer with a thickness of 10 μm. The alumina ceramic substrate is then dried, and then heated to 850℃±5℃ at a heating rate of 10℃ / min and held for 10 min. After cooling, a PTC thermistor film is obtained.

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