Barium titanate-based ptc ceramic and method for producing the same

Abstract

The application provides a barium titanate-based PTC ceramic and a preparation method thereof. The preparation method comprises the following steps: weighing primary raw materials, wherein the primary raw materials comprise BaCO3, TiO2, SrCO3 and Y2O3; performing primary ball milling and primary drying on the primary raw materials in sequence to obtain primary powder; performing calcination on the primary powder to obtain calcined materials; mixing the calcined materials and a sintering aid, and performing secondary ball milling and secondary drying on the obtained mixture in sequence to obtain secondary powder; mixing the secondary powder, a binder and a lubricant to obtain mixed granules; performing tabletting on the mixed granules to obtain a green body; and performing degassing sintering on the green body to obtain the barium titanate-based PTC ceramic, wherein the Curie temperature of the barium titanate-based PTC ceramic is 0-90 ℃, and the order of magnitude of the room temperature resistivity is 10 5 ~ 10 8 Ω·cm. The barium titanate-based PTC ceramic prepared by the application has low Curie temperature and high room temperature resistivity characteristics, and maintains excellent PTC characteristics.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of ceramic materials, and in particular, to a barium titanate-based PTC ceramic and a preparation method thereof. BACKGROUND

[0002] Semiconductor ceramic-based BaTiO3 material (PTC material) has the characteristics of low preparation cost, simple preparation method, controllable Curie temperature and the like. Normal temperature resistivity (25℃ corresponding resistivity) and Curie temperature are two important parameters of BaTiO3-based PTC material. Nowadays, semiconductor ceramic-based BaTiO3 is widely used in many fields (such as: household appliances, electronic equipment, aviation), and the research on low resistance and high Curie temperature of ceramic materials has made great progress, the normal temperature resistivity reaches about 10Ω·cm, and the Curie temperature reaches about 600℃. In recent years, PTC materials have been gradually applied to the insulation field, but PTC materials are required to have the characteristics of low Curie temperature and high normal temperature resistivity. Therefore, it is necessary to design a preparation method for PTC materials with excellent PTC effect, low Curie temperature and high normal temperature resistivity. SUMMARY

[0003] The present application aims to at least solve one of the technical problems in the related art. To this end, one object of the present application is to propose a method for preparing a barium titanate-based PTC ceramic, which has the characteristics of low Curie temperature and high normal temperature resistivity, maintains excellent PTC characteristics, and has a simple preparation process and low cost.

[0004] In a first aspect of the present application, a method for preparing a barium titanate-based PTC ceramic is provided. According to an embodiment of the present application, the method for preparing a barium titanate (BaTiO3)-based PTC ceramic includes the following steps: weighing a primary raw material, the primary raw material including BaCO3, TiO2, SrCO3 and Y2O3; sequentially performing primary ball milling and primary drying on the primary raw material to obtain a primary powder; calcining the primary powder to obtain a calcined material; mixing the calcined material and a sintering aid, and sequentially performing secondary ball milling and secondary drying on the obtained mixture to obtain a secondary powder; mixing the secondary powder with a binder and a lubricant to obtain a mixed granule; performing tabletting on the mixed granule to obtain a green body; performing degassing sintering on the green body to obtain the barium titanate-based PTC ceramic, the barium titanate-based PTC ceramic having a Curie temperature of 0℃-90℃ and a normal temperature resistivity of the order of magnitude of 10 5 ~10 8Ω*cm. Thus, the barium titanate-based PTC ceramic prepared by the method has low Curie temperature and high room temperature resistivity characteristics, and maintains excellent PTC characteristics. The application utilizes doping modification, first adding strontium carbonate into the barium titanate, and calcining to generate barium strontium titanate. The low-melting-point strontium titanate can reduce the melting temperature of the barium titanate, thereby reducing the Curie temperature of the ceramic material. Meanwhile, Y2O3 is used as a semi-conducting agent, Y acts as a donor element and an acceptor element, the resistivity of the material is controlled, and the ceramic material is semi-conducting. Meanwhile, the barium titanate-based PTC ceramic is targetedly controlled by doping Sr and Y, the low Curie temperature and high room temperature resistivity are cooperatively designed, the Curie temperature of the PTC ceramic is reduced to 0-90 DEG C, and the room temperature resistivity is ensured to be in the order of 10 5 ~10 8 orders of magnitude, which meets new requirements of PTC ceramic materials in the insulation field. In addition, the method for preparing the barium titanate-based PTC ceramic of the application uses a traditional solid-phase method, and the preparation process is lead-free, environmentally friendly, simple, and low in cost, and is suitable for batch industrial production.

[0005] According to the embodiment of the application, the primary raw material comprises, in terms of mole fraction, 0.1-1 parts of BaCO3, 0.1-1 parts of SrCO3, 0.2-1.5 parts of TiO2, and 0.0001-0.005 parts of Y2O3, and optionally, the mole quantity of titanium atoms is equal to the sum of the mole quantity of barium atoms and the mole quantity of strontium atoms in the primary raw material.

[0006] According to the embodiment of the application, the primary ball milling satisfies at least one of the following conditions: the mass ratio of the first grinding medium to the primary raw material is (1-3):1; the mass ratio of the first ball milling dispersion medium to the primary raw material is (1-3):1; the rotation speed of the primary ball milling is 200-250 r / min; the ball milling time is 15 h-30 h, and the ball milling is performed for 10 min-30 min, with an intermittent time of 1 min-5 min, and the mode of the primary ball milling is set to positive and negative rotation alternately, and optionally, the temperature of the primary drying is 50 DEG C-80 DEG C, and the time is 3 h-12 h.

[0007] According to the embodiment of the application, the calcining temperature is 1100-1250 DEG C, and the holding time is 1 h-4 h.

[0008] According to the embodiment of the application, the sintering aid comprises, in terms of mole fraction, 0.001-0.01 parts of Al2O3, 0.01-0.05 parts of SiO2, and 0.003-0.015 parts of TiO2.

[0009] According to the embodiment of the present application, the secondary ball milling satisfies at least one of the following conditions: the mass ratio of the second grinding medium to the calcined material is (1-3):1; the mass ratio of the second ball milling dispersion medium to the calcined material is (1-3):1; the rotation speed of the secondary ball milling is 200-250 r / min; the ball milling time is 15-30 h, and the ball milling is performed for 10-30 min, with an intermittent time of 1-5 min, and the mode of the secondary ball milling is set to be positive and negative rotation alternately; and optionally, the temperature of the secondary drying is 50-80℃, and the time is 3-12 h.

[0010] According to the embodiment of the present application, the mixed granules satisfy at least one of the following conditions: the binder comprises at least one of polyvinyl alcohol solution, phenolic resin solution, epoxy resin solution and vinyl butyral solution; the lubricant comprises at least one of glycerol, calcium stearate and magnesium stearate; the mass fraction of the lubricant is 0.1%-1%, the mass fraction of the binder is 14.9%-24%, and the mass fraction of the secondary powder is 75%-85% based on the total mass of the mixed granules; and the mixed granules are further subjected to grinding and sieving treatment, and the mesh number of the sieving screen is 20-60 mesh and 100-300 mesh.

[0011] According to the embodiment of the present application, the pressure of the tabletting is 5-10 MPa, and the pressure maintaining time is 1-10 min; and optionally, the mixed granules are subjected to pretreatment before the tabletting, and the pretreatment is that the mixed granules are placed in a sealed environment for 10-48 h.

[0012] According to the embodiment of the present application, the glue removal sintering comprises: gradually increasing the temperature of the green body from room temperature to a glue removal temperature of 200-900℃ at a temperature increasing rate of 0.4-4.0℃ / min, and maintaining the temperature for 10-60 min; increasing the temperature from the glue removal temperature to an intermediate temperature of 1000-1250℃ at a temperature increasing rate of 1-10℃ / min; increasing the temperature from the intermediate temperature to a sintering temperature of 1250-1500℃ at a temperature increasing rate of 2-16℃ / min, and maintaining the temperature for 1-5 h; decreasing the temperature from the sintering temperature to the intermediate temperature at a temperature decreasing rate of 2-16℃ / min; and cooling the temperature from the intermediate temperature to room temperature with the furnace.

[0013] In another aspect of the present application, the present application provides a barium titanate-based PTC ceramic. According to an embodiment of the present application, the barium titanate-based PTC ceramic is prepared by the method described above, and optionally, the barium titanate-based PTC ceramic further satisfies at least one of the following conditions: the barium titanate-based PTC ceramic is pseudo-tetragonal phase; the grain size of the barium titanate-based PTC ceramic is 1 μm to 30 μm; and the relative density of the barium titanate-based PTC ceramic is 90% to 99%. Thus, the barium titanate-based PTC ceramic has both a low Curie temperature and a high room temperature resistivity, the Curie temperature is 0°C to 90°C, and the room temperature resistivity is in the order of 10 5 8 Ω·cm, which satisfies the use requirements of PTC ceramic materials in the insulation field, and further expands the application field of barium titanate-based PTC ceramics. BRIEF DESCRIPTION OF DRAWINGS

[0014] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the following drawings, in which:

[0015] Figure 1 is a flow chart of a method for preparing a barium titanate-based PTC ceramic in an embodiment of the present application.

[0016] Figure 2 is an XRD pattern of a barium titanate-based PTC ceramic prepared in Examples 1-4 and Comparative Example 1 of the present application at room temperature.

[0017] Figure 3 is an SEM image of a barium titanate-based PTC ceramic sample prepared in Examples 1-4 and Comparative Example 1 of the present application.

[0018] Figure 4 is a curve of the Curie temperature of a barium titanate-based PTC ceramic prepared in Examples 1-4 and Comparative Example 1 of the present application versus the Y2O3 doping concentration.

[0019] Figure 5 is a curve of the room temperature (temperature of 25°C) resistivity of a barium titanate-based PTC ceramic prepared in Examples 1-4 and Comparative Example 1 of the present application versus the Y2O3 doping concentration.

[0020] Figure 6 is a curve of the relative density of a barium titanate-based PTC ceramic prepared in Examples 1-4 and Comparative Example 1 of the present application versus the Y2O3 doping concentration. DETAILED DESCRIPTION

[0021] ​The present invention will be explained below with reference to embodiments. Those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of the invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0022] The present invention will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present invention in any way.

[0023] In a first aspect, the present invention provides a method for preparing barium titanate-based PTC ceramics. According to an embodiment of the present invention, referring to… Figure 1 The method for preparing barium titanate (BaTiO3) based PTC ceramics includes the following steps:

[0024] S100: Weigh the primary raw materials, which include BaCO3, TiO2, SrCO3 and Y2O3.

[0025] According to embodiments of the present invention, the primary raw materials, by molar parts, include: 0.1–1 parts of BaCO3, 0.1–1 parts of SrCO3, 0.2–1.5 parts of TiO2, and 0.0001–0.005 parts of Y2O3. Under the above proportions, high-performance barium titanate (BaTiO3)-based PTC ceramics can be effectively prepared, exhibiting both low Curie temperature and high room-temperature resistivity while maintaining PTC characteristics. Specifically, the PTC characteristic refers to the fact that the resistivity of barium titanate (BaTiO3)-based PTC ceramics is very low at room temperature, but increases suddenly by thousands to millions of times as the temperature rises to a certain specific temperature (transition temperature), and then returns to its original state when the temperature drops.

[0026] In some embodiments of the present invention, the molar amount of titanium atoms in the primary raw material is equal to the sum of the molar amounts of barium atoms and strontium atoms. Using the above molar ratio in the primary raw material allows for full utilization of the primary raw material during the subsequent calcination reaction. This is because adding strontium carbonate to barium titanate and calcining it produces barium strontium titanate, which has an oxygen octahedral structure and the molecular formula Ba. (1-x) Sr xTiO3 requires one Ti atom to balance the divalent Ba and Sr atoms and the three divalent O atoms. In other words, when strontium is doped into barium titanate, Sr atoms replace the Ba atoms in the original BaTiO3, forming barium strontium titanate, where the number of titanium atoms equals the sum of the number of barium and strontium atoms. Therefore, using the above-mentioned proportions of raw materials for primary calcination allows for the full utilization of titanium, barium, and strontium atoms, significantly improving raw material utilization, avoiding waste, and resulting in a purer calcined product.

[0027] S200: The raw material is subjected to ball milling and drying once in sequence to obtain powder.

[0028] In some implementations, the mass ratio of the first grinding media to the primary raw material used in primary grinding ball milling is (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. This ratio ensures that the grinding media thoroughly grinds the primary raw material, contributing to the obtaining of a primary powder with a relatively uniform particle size. The specific material of the first grinding media is not particularly important; those skilled in the art can choose it flexibly according to actual needs. For example, the first grinding media can be at least one of zirconia balls and agate balls.

[0029] In some implementations, the mass ratio of the first ball milling dispersion medium to the primary raw material used in the primary ball milling is (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. These ratios ensure uniform dispersion of the primary raw material during ball milling, resulting in a primary powder with a relatively uniform particle size. The specific material of the first ball milling dispersion medium is not particularly important; those skilled in the art can choose it flexibly according to actual needs. For example, the first ball milling dispersion medium can be anhydrous ethanol, thus avoiding damage to the various components of the primary raw material.

[0030] In some implementations, the ball milling speed is 200-250 r / min, such as 200 r / min, 205 r / min, 210 r / min, 215 r / min, 220 r / min, 225 r / min, 230 r / min, 235 r / min, 240 r / min, 245 r / min, 250 r / min, etc. Under the above speed conditions, the raw materials can be effectively and uniformly ball-milled.

[0031] In some implementations, the ball milling time for a single session is 15 to 30 hours (e.g., 15, 16, 17, 18, 19, 20, 22, 24, 25, 27, 29, 30 hours), with each milling session lasting 10 to 30 minutes (e.g., 10, 12, 15, 18, 20, 23, 25, 28, 30 minutes), and the interval between milling sessions lasting 1 to 5 minutes (e.g., 1 minute, 2 minutes, etc.). The ball milling process is set to alternate between forward and reverse rotation (3 min, 4 min, 5 min). That is, during one ball milling cycle, milling is performed in the first direction for 10-30 minutes, then stopped and paused for 1-5 minutes. Then, milling is performed in the second direction for 10-30 minutes, then stopped and paused for 1-5 minutes, and so on, completing the sequential milling process. This ball milling method and parameters are beneficial for reducing the particle size of the raw material and increasing the uniformity of the powder mixing. One of the first and second directions is clockwise, and the other is counterclockwise. It should be noted that the ball milling time of 15-30 hours refers only to the actual milling time and does not include the pause time.

[0032] According to an embodiment of the present invention, the drying temperature in step 200 is 50°C to 80°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C), and the time is 3h to 12h (e.g., 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h). Under the above conditions, the drying temperature is lower than or close to the boiling point of the first ball milling dispersion medium (anhydrous ethanol), which is beneficial for accelerating evaporation and will not cause the slurry to boil, reducing experimental risks. This time length helps the material to be fully dried.

[0033] S300: Calcining a primary powder to obtain calcined material.

[0034] According to embodiments of the present invention, the calcination temperature is 1100–1250°C, for example, 1100°C, 1130°C, 1150°C, 1180°C, 1200°C, 1220°C, or 1250°C, and the holding time is 1 hour–4 hours, for example, 1 hour, 2 hours, 3 hours, or 4 hours. Under the above calcination conditions, it is beneficial to ensure complete calcination, allowing unreacted raw materials in the primary powder to fully react.

[0035] In some embodiments, the calcination step can be carried out in an air atmosphere, which greatly reduces the difficulty of preparing barium titanate-based PTC ceramics.

[0036] S400: The calcining material and calcining aid are mixed, and the resulting mixture is subjected to secondary ball milling and secondary drying to obtain secondary powder.

[0037] According to embodiments of the present invention, the sintering aid comprises, by molar amounts, 0.001 to 0.01 parts of Al₂O₃, 0.01 to 0.05 parts of SiO₂, and 0.003 to 0.015 parts of TiO₂. The aforementioned sintering aid can help improve the overall performance of barium titanate-based PTC ceramics. In some embodiments, the total amount of step S100 and the TiO₂ added in this step can be 0.5 to 1.5 molar amounts.

[0038] In some implementations, the mass ratio of the second grinding media to the calcined material used in the secondary grinding ball mill is (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. These ratios ensure that the grinding media thoroughly grinds the raw material in the first stage, contributing to the production of secondary powder with a more uniform particle size. The specific material of the second grinding media is not particularly important; those skilled in the art can choose flexibly according to actual needs. For example, the second grinding media can be at least one of zirconia balls and agate balls.

[0039] In some implementations, the mass ratio of the second ball milling dispersion medium to the calcined material used in the secondary ball milling is (1-3):1, such as 1:1, 1.5:1, 2:1, 2.5:1, or 3:1. These ratios ensure uniform dispersion of the calcined material during ball milling, resulting in secondary powders with relatively uniform particle size. The specific material of the second ball milling dispersion medium is not particularly important; those skilled in the art can choose flexibly according to actual needs. For example, anhydrous ethanol can be used as the second ball milling dispersion medium, thus avoiding damage to the various components in the calcined material.

[0040] In some implementations, the rotational speed of the secondary ball mill is 200-250 r / min, such as 200 r / min, 205 r / min, 210 r / min, 215 r / min, 220 r / min, 225 r / min, 230 r / min, 235 r / min, 240 r / min, 245 r / min, 250 r / min, etc. Under the above rotational speed conditions, the calcined material can be effectively and uniformly ball-milled.

[0041] In some implementations, the ball milling time for the second ball mill is 15h to 30h (e.g., 15h, 16h, 17h, 18h, 19h, 20h, 22h, 24h, 25h, 27h, 29h, 30h), and the ball milling time is 10min to 30min (e.g., 10min, 12min, 15min, 18min, 20min, 23min, 25min, 28min, 30min), with an interval time of 1min to 5min (e.g., 1min, 2min). The secondary ball milling process is set to alternate between forward and reverse rotation (10-30 minutes, 3 minutes, 4 minutes, 5 minutes). That is, during the secondary ball milling process, ball milling is performed in the first direction for 10-30 minutes, then stopped and paused for 1-5 minutes. Then, ball milling is performed in the second direction for 10-30 minutes, then stopped and paused for 1-5 minutes, and this process is repeated sequentially. This ball milling method and parameters are beneficial for reducing the particle size of the calcined material and increasing the uniformity of the secondary powder mixing. One of the first and second directions is clockwise, and the other is counterclockwise. It should be noted that the ball milling time of 15-30 hours refers only to the actual milling time and does not include the pause time.

[0042] S500: Mix secondary powder with binder and lubricant to obtain mixed granules.

[0043] In some embodiments, the binder in the above steps includes at least one of polyvinyl alcohol solution, phenolic resin solution, epoxy resin polysol, and vinyl butyral solution. These binders are widely available, have good performance, and can effectively improve product performance. In some specific embodiments, polyvinyl alcohol solution can be selected as the binder. Polyvinyl alcohol is simple and convenient to use, low in cost, has strong adhesion, and is non-toxic and pollution-free. The solvent in the polyvinyl alcohol solution can be deionized water. Furthermore, the mass fraction of the solute in the binder is 5% to 10%, for example, the mass fraction of polyvinyl alcohol in the polyvinyl alcohol solution is 5% to 10%.

[0044] In some embodiments, the lubricant includes at least one of glycerin, calcium stearate, and magnesium stearate. These lubricants are non-toxic, non-polluting, and provide excellent performance at a low cost.

[0045] In some embodiments of the present invention, based on the total mass of the mixed granules, the mass fraction of the lubricant is 0.1% to 1% (e.g., 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%), the mass fraction of the binder is 14.9% to 24% (e.g., 14.9%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%), and the mass fraction of the secondary powder is 75% to 85% (e.g., 75%, 76%, 77%, 78%, 79%, 80%, 81%, 82%, 83%, 84%, 85%). The mixed granules in the above proportions can be used to prepare barium titanate-based PTC ceramics with the desired properties. The lubricant in the above proportion can ensure uniform dispersion of raw materials during the preparation of barium titanate-based PTC ceramics, reduce friction between components in the raw materials, and facilitate subsequent grinding processes; the binder in the above proportion can improve the adhesion between components in the subsequent tableting process, which is helpful for tableting.

[0046] In some embodiments, the mixed granules are further ground and sieved using sieves with mesh sizes of 20–60 mesh and 100–300 mesh. This allows for the screening and uniformization of granules, which improves granule flowability during tableting, prevents cracking and delamination in the green body, and thus helps improve the performance of the prepared barium titanate-based PTC ceramics. In some embodiments, sieves of 30–50 mesh and 150–250 mesh can be selected; in some specific embodiments, sieves of 40 mesh and 200 mesh can be selected.

[0047] S600: Compress the mixed granules into tablets to obtain green compacts.

[0048] In some embodiments, the mixed granules are pretreated before tableting. Pretreatment involves placing the mixed granules in a sealed environment for 10 to 48 hours (this process can be called aging), such as 10, 12, 15, 18, 20, 23, 25, 30, 35, 40, 45, or 48 hours. This ensures that the mixed granules are in a uniform environment, which is beneficial for the uniformity of moisture content in the mixed granules.

[0049] According to embodiments of the present invention, the pressing pressure is 5 MPa to 10 MPa, for example, 5 MPa, 6 MPa, 7 MPa, 8 MPa, 9 MPa, or 10 MPa, and the holding time is 1 min to 10 min, for example, 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, or 10 min. Under the above pressing conditions, the smooth forming of the compact can be effectively ensured, while also improving the internal bonding strength and density of PTC ceramic materials with low Curie temperature and high room temperature resistivity characteristics.

[0050] S700: The green body is debinded and sintered to obtain barium titanate-based PTC ceramics. The Curie temperature of barium titanate-based PTC ceramics is 0℃~90℃, and the resistivity at room temperature is on the order of 10. 5 ~10 8 Ω·cm.

[0051] According to an embodiment of the present invention, the above-described debinding and sintering step includes:

[0052] 1) Gradually raise the temperature of the green body from room temperature to the debinding temperature of 200℃~900℃ (e.g., 200℃, 250℃, 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, 700℃, 750℃, 800℃, 850℃, 900℃), with a heating rate of 0.4℃ / min~4.0℃ / min (e.g., 0.4℃ / min, 0.5℃ / min, 1.0℃ / min, 1.5℃ / min, 2.0℃ / min, 2.5℃ / min, 3.0℃ / min, 3.5℃ / min, 4.0℃ / min), and hold the temperature for 10min~60min (e.g., 10min, 20min, 30min, 40min, 50min, 60min);

[0053] 2) Raise the temperature from the discharge temperature to an intermediate temperature of 1000-1250℃ (e.g., 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃), with a heating rate of 1℃ / min to 10℃ / min (e.g., 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min);

[0054] 3) Raise the temperature from the intermediate temperature to the sintering temperature of 1250-1500℃ (e.g., 1250℃, 1300℃, 1350℃, 1400℃, 1450℃, 1500℃), with a heating rate of 2℃ / min to 16℃ / min (e.g., 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, 16℃ / min), and hold for 1h to 5h (e.g., 1h, 2h, 3h, 4h, 5h).

[0055] 4) Reduce the temperature from the sintering temperature to the intermediate temperature at a rate of 2℃ / min to 16℃ / min (e.g., 2℃ / min, 3℃ / min, 4℃ / min, 5℃ / min, 6℃ / min, 7℃ / min, 8℃ / min, 9℃ / min, 10℃ / min, 11℃ / min, 12℃ / min, 13℃ / min, 14℃ / min, 15℃ / min, 16℃ / min); wherein, the specific temperature value of the temperature rise from the debinding temperature to the intermediate temperature in the above-mentioned step can be the same as or different from the temperature value of the temperature drop to the intermediate temperature in this step, as long as it is within the range of 1000 to 1250℃.

[0056] 5) Cool from the intermediate temperature to room temperature with the furnace.

[0057] In the above-mentioned debinding and sintering process, the present invention controls the debinding temperature and holding time to prevent the material from generating pores and cracks during debinding. During the sintering process, the temperature is first raised to an intermediate temperature T1 and then rapidly raised to the sintering temperature. By controlling the holding temperature and time, the material is fully sintered.

[0058] In some embodiments, the debinding sintering step can be carried out in an air atmosphere, which greatly reduces the difficulty of preparing barium titanate-based PTC ceramics.

[0059] According to embodiments of the present invention, the barium titanate-based PTC ceramics prepared by the above method exhibit low Curie temperature and high room-temperature resistivity while maintaining their excellent PTC properties. The present invention utilizes doping modification. First, strontium carbonate is added to barium titanate, and calcination is performed to generate barium strontium titanate. The low-melting-point strontium titanate lowers the melting temperature of barium titanate, thereby reducing the Curie temperature of the ceramic material. Simultaneously, Y₂O₃ is used as a semiconducting agent, with Y acting as both a donor and acceptor element to regulate the resistivity of the material, making the ceramic material semiconducting. Furthermore, targeted regulation of the BaTiO₃-based PTC ceramics through Sr and Y doping achieves a synergistic design of low Curie temperature and high room-temperature resistivity, reducing the Curie temperature of the PTC ceramic to 0℃~90℃ while maintaining a room-temperature resistivity of 10.5 ~10 8 This achievement represents a significant improvement, meeting the new requirements for PTC ceramic materials in the insulation field. Specifically, by adjusting the doping ratio of each raw material, the microstructure and related properties of barium titanate-based PTC ceramics are significantly altered, reducing the Curie temperature and synergistically controlling the room-temperature resistivity to within 10-1. 5 ~10 8 Order of magnitude. Furthermore, the method for preparing barium titanate-based PTC ceramics in this invention uses a traditional solid-state method, which is lead-free, environmentally friendly, simple, and low-cost, making it suitable for mass industrial production.

[0060] In another aspect, the present invention provides a barium titanate-based PTC ceramic. According to an embodiment of the invention, this barium titanate-based PTC ceramic is prepared by the method described above. Thus, this barium titanate-based PTC ceramic simultaneously possesses a low Curie temperature (0°C to 90°C) and a high room-temperature resistivity, with the Curie temperature ranging from 0°C to 90°C and the room-temperature resistivity on the order of 10⁻⁶. 5 ~10 8 The Ω·cm value meets the requirements for PTC ceramic materials in the insulation field, thereby expanding the application areas of barium titanate-based PTC ceramics.

[0061] According to an embodiment of the present invention, barium titanate-based PTC ceramics are pseudo-tetragonal phases. A pseudo-tetragonal phase refers to a crystal exhibiting tetragonal symmetry in a diffraction pattern, but whose actual unit cell parameters are not truly tetragonal. This phenomenon is usually caused by a certain degree of distortion or aberration within the crystal. Therefore, in the barium titanate-based PTC ceramic material prepared by the above method, the Y element has been doped into the material's unit cell, altering the lattice parameters and thus affecting properties such as the Curie temperature.

[0062] In some embodiments of the present invention, the grain size of barium titanate-based PTC ceramics is 1 μm to 30 μm. It can be seen that doping with Y element reduces the grain size of the material. Since grain size is related to the Curie temperature of the material, when the grain size decreases to a certain extent, the size effect leads to a decrease in the Curie temperature. Therefore, doping with Y element helps to regulate the Curie temperature and room temperature resistivity of the material.

[0063] In some embodiments of the present invention, the relative density of barium titanate-based PTC ceramics is 90% to 99%. Therefore, the barium titanate-based PTC ceramic material prepared by the present invention maintains good application performance while exhibiting a low Curie temperature and high room-temperature resistivity.

[0064] Example

[0065] Example 1

[0066] The steps for preparing barium titanate-based PTC ceramics are as follows:

[0067] Weigh out the raw materials. The raw materials contain 0.7 mol BaCO3, 0.3 mol SrCO3, 1.0 mol TiO2, and 0.0008 mol Y2O3.

[0068] Zirconia balls were used as the grinding media and ethanol as the dispersion media. The mass ratio of dispersion media to raw materials was controlled at 1.5:1 and the mass ratio of grinding media to raw materials was 2:1. The mixture was added to a nylon ball mill jar for a single wet planetary ball milling process at a speed of 225 r / min for 24 h. After the ball milling was completed, the slurry was placed in a 70℃ oven for 6 h to dry, resulting in a uniformly mixed and dried primary powder.

[0069] Weigh out the above-mentioned uniformly mixed primary powder and place it in a crucible. Calcinate it at 1190°C for 3 hours in an air-atmosphere high-temperature tube furnace to obtain the calcined material.

[0070] The calcined material, weighed calcining aid, and ethanol were placed together in a nylon ball mill jar for a second wet planetary ball milling process. The ball milling and drying parameters were set the same as those for the first ball milling. After drying, a secondary powder was obtained, in which the calcining aid consisted of 0.01 mol TiO2, 0.005 mol Al2O3, and 0.024 mol SiO2.

[0071] After the secondary powder is ball-milled twice, 20wt% of a polyvinyl alcohol solution with a mass fraction of 8% and 0.5wt% of glycerol are slowly added. During the addition process, the powder is continuously ground and the granules are screened with 40-mesh and 200-mesh sieves to obtain mixed granules.

[0072] The above-obtained mixed granules were sealed and aged for 24 hours before being pressed into tablets. First, a certain amount of the aged mixed granules was weighed and placed into a mold, then pressed to 7.5 MPa and held for 5 minutes to obtain a green sheet with a diameter of 20 mm and a thickness of 2 mm.

[0073] The green body is placed in an air-atmosphere tube furnace for debinding and sintering. To remove polyvinyl alcohol from the green body, the temperature is increased from room temperature to 400°C at a rate of 1.5°C / min and held for 30 minutes to ensure complete debinding. Then, the temperature is increased to 1150°C at a rate of 2.5°C / min, and then to 1350°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1150°C at a rate of 10°C / min, and then to 500°C at a rate of 1.5°C / min. Finally, the furnace is cooled to room temperature to obtain barium titanate-based PTC ceramic material.

[0074] The XRD pattern of the prepared barium titanate-based PTC ceramic material at room temperature is as follows:Figure 2 As shown in (d) above, the SEM image of the barium titanate-based PTC ceramic material is as follows: Figure 3 As shown in (b) above, the Curie temperature, room temperature resistivity, and relative density can be referenced from [reference]. Figure 4 , Figure 5 and Figure 6 .

[0075] Example 2

[0076] The steps for preparing barium titanate-based PTC ceramics are as follows:

[0077] Weigh out the raw materials. The raw materials contain 0.7 mol BaCO3, 0.3 mol SrCO3, 1.0 mol TiO2, and 0.0016 mol Y2O3.

[0078] Zirconia balls were used as the grinding media and ethanol as the dispersion media. The mass ratio of dispersion media to raw materials was controlled at 1.5:1 and the mass ratio of grinding media to raw materials was 2:1. The mixture was added to a nylon ball mill jar for a single wet planetary ball milling process at a speed of 225 r / min for 24 h. After the ball milling was completed, the slurry was placed in a 70℃ oven for 6 h to dry, resulting in a uniformly mixed and dried primary powder.

[0079] Weigh out the above-mentioned uniformly mixed primary powder and place it in a crucible. Calcinate it at 1190°C for 3 hours in an air-atmosphere high-temperature tube furnace to obtain the calcined material.

[0080] The calcined material, weighed calcining aid, and ethanol were placed together in a nylon ball mill jar for a second wet planetary ball milling process. The ball milling and drying parameters were set the same as those for the first ball milling. After drying, a secondary powder was obtained, in which the calcining aid included 0.01 mol TiO2, 0.005 mol Al2O3, and 0.024 mol SiO2.

[0081] After the secondary powder is ball-milled twice, 20wt% of a polyvinyl alcohol solution with a mass fraction of 8% and 0.5wt% of glycerol are slowly added. During the addition process, the powder is continuously ground and the granules are screened with 40-mesh and 200-mesh sieves to obtain mixed granules.

[0082] The above-obtained mixed granules were sealed and aged for 24 hours before being pressed into tablets. First, a certain amount of the aged mixed granules was weighed and placed into a mold, then pressed to 7.5 MPa and held for 5 minutes to obtain a green sheet with a diameter of 20 mm and a thickness of 2 mm.

[0083] The green body is placed in an air-atmosphere tube furnace for debinding and sintering. To remove polyvinyl alcohol from the green body, the temperature is increased from room temperature to 400°C at a rate of 1.5°C / min and held for 30 minutes to ensure complete debinding. Then, the temperature is increased to 1150°C at a rate of 2.5°C / min, and then to 1350°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1150°C at a rate of 10°C / min, and then to 500°C at a rate of 1.5°C / min. Finally, the furnace is cooled to room temperature to obtain barium titanate-based PTC ceramic material.

[0084] The XRD pattern of the prepared barium titanate-based PTC ceramic material at room temperature is as follows: Figure 2 As shown in (c) above, the SEM image of the barium titanate-based PTC ceramic material is as follows: Figure 3 As shown in (c), the Curie temperature, room temperature resistivity, and relative density can be referenced from [reference]. Figure 4 , Figure 5 and Figure 6 .

[0085] Example 3

[0086] The steps for preparing barium titanate-based PTC ceramics are as follows:

[0087] Weigh out the raw materials. The raw materials contain 0.7 mol BaCO3, 0.3 mol SrCO3, 1.0 mol TiO2, and 0.0024 mol Y2O3.

[0088] Zirconia balls were used as the grinding media and ethanol as the dispersion media. The mass ratio of dispersion media to raw materials was controlled at 1.5:1 and the mass ratio of grinding media to raw materials was 2:1. The mixture was added to a nylon ball mill jar for a single wet planetary ball milling process at a speed of 225 r / min for 24 h. After the ball milling was completed, the slurry was placed in a 70℃ oven for 6 h to dry, resulting in a uniformly mixed and dried primary powder.

[0089] Weigh out the above-mentioned uniformly mixed primary powder and place it in a crucible. Calcinate it at 1190°C for 3 hours in an air-atmosphere high-temperature tube furnace to obtain the calcined material.

[0090] The calcined material, weighed calcining aid, and ethanol were placed together in a nylon ball mill jar for a second wet planetary ball milling process. The ball milling and drying parameters were set the same as those for the first ball milling. After drying, a secondary powder was obtained, in which the calcining aid included 0.01 mol TiO2, 0.005 mol Al2O3, and 0.024 mol SiO2.

[0091] After the secondary powder is ball-milled twice, 20wt% of a polyvinyl alcohol solution with a mass fraction of 8% and 0.5wt% of glycerol are slowly added. During the addition process, the powder is continuously ground and the granules are screened with 40-mesh and 200-mesh sieves to obtain mixed granules.

[0092] The above-obtained mixed granules were sealed and aged for 24 hours before being pressed into tablets. First, a certain amount of the aged mixed granules was weighed and placed into a mold, then pressed to 7.5 MPa and held for 5 minutes to obtain a green sheet with a diameter of 20 mm and a thickness of 2 mm.

[0093] The green body is placed in an air-atmosphere tube furnace for debinding and sintering. To remove polyvinyl alcohol from the green body, the temperature is increased from room temperature to 400°C at a rate of 1.5°C / min and held for 30 minutes to ensure complete debinding. Then, the temperature is increased to 1150°C at a rate of 2.5°C / min, and then to 1350°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1150°C at a rate of 10°C / min, and then to 500°C at a rate of 1.5°C / min. Finally, the furnace is cooled to room temperature to obtain barium titanate-based PTC ceramic material.

[0094] The XRD pattern of the prepared barium titanate-based PTC ceramic material at room temperature is as follows: Figure 2 As shown in (b) above, the SEM image of the barium titanate-based PTC ceramic material is as follows: Figure 3 As shown in (d) in the figure, the Curie temperature, room temperature resistivity, and relative density can be referenced from [reference]. Figure 4 , Figure 5 and Figure 6 .

[0095] Example 4

[0096] The steps for preparing barium titanate-based PTC ceramics are as follows:

[0097] Weigh out the raw materials. The raw materials contain 0.7 mol BaCO3, 0.3 mol SrCO3, 1.0 mol TiO2, and 0.0032 mol Y2O3.

[0098] Zirconia balls were used as the grinding media and ethanol as the dispersion media. The mass ratio of dispersion media to raw materials was controlled at 1.5:1 and the mass ratio of grinding media to raw materials was 2:1. The mixture was added to a nylon ball mill jar for a single wet planetary ball milling process at a speed of 225 r / min for 24 h. After the ball milling was completed, the slurry was placed in a 70℃ oven for 6 h to dry, resulting in a uniformly mixed and dried primary powder.

[0099] Weigh out the above-mentioned uniformly mixed primary powder and place it in a crucible. Calcinate it at 1190°C for 3 hours in an air-atmosphere high-temperature tube furnace to obtain the calcined material.

[0100] The calcined material, weighed calcining aid, and ethanol were placed together in a nylon ball mill jar for a second wet planetary ball milling process. The ball milling and drying parameters were set the same as those for the first ball milling. After drying, a secondary powder was obtained, in which the calcining aid included 0.01 mol TiO2, 0.005 mol Al2O3, and 0.024 mol SiO2.

[0101] After the secondary powder is ball-milled twice, 20wt% of a polyvinyl alcohol solution with a mass fraction of 8% and 0.5wt% of glycerol are slowly added. During the addition process, the powder is continuously ground and the granules are screened with 40-mesh and 200-mesh sieves to obtain mixed granules.

[0102] The above-obtained mixed granules were sealed and aged for 24 hours before being pressed into tablets. First, a certain amount of the aged mixed granules was weighed and placed into a mold, then pressed to 7.5 MPa and held for 5 minutes to obtain a green sheet with a diameter of 20 mm and a thickness of 2 mm.

[0103] The green body is placed in an air-atmosphere tube furnace for debinding and sintering. To remove polyvinyl alcohol from the green body, the temperature is increased from room temperature to 400°C at a rate of 1.5°C / min and held for 30 minutes to ensure complete debinding. Then, the temperature is increased to 1150°C at a rate of 2.5°C / min, and then to 1350°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1150°C at a rate of 10°C / min, and then to 500°C at a rate of 1.5°C / min. Finally, the furnace is cooled to room temperature to obtain barium titanate-based PTC ceramic material.

[0104] The XRD pattern of the prepared barium titanate-based PTC ceramic material at room temperature is as follows: Figure 2 As shown in (a) above, the SEM image of the barium titanate-based PTC ceramic material is as follows: Figure 3 As shown in (e), the Curie temperature, room temperature resistivity, and relative density can be referenced from [reference]. Figure 4 , Figure 5 and Figure 6 .

[0105] Comparative Example 1

[0106] The steps for preparing barium titanate-based PTC ceramics are as follows:

[0107] Weigh out the primary raw materials, which contain 0.7 mol BaCO3, 0.3 mol SrCO3, and 1.0 mol TiO2. Y2O3 doping is not performed in this comparative example.

[0108] Zirconia balls were used as the grinding media and ethanol as the dispersion media. The mass ratio of dispersion media to raw materials was controlled at 1.5:1 and the mass ratio of grinding media to raw materials was 2:1. The mixture was added to a nylon ball mill jar for a single wet planetary ball milling process at a speed of 225 r / min for 24 h. After the ball milling was completed, the slurry was placed in a 70℃ oven for 6 h to dry, resulting in a uniformly mixed and dried primary powder.

[0109] Weigh out the above-mentioned uniformly mixed primary powder and place it in a crucible. Calcinate it at 1190°C for 3 hours in an air-atmosphere high-temperature tube furnace to obtain the calcined material.

[0110] The calcined material, weighed calcining aid, and ethanol were placed together in a nylon ball mill jar for a second wet planetary ball milling process. The ball milling and drying parameters were set the same as those for the first ball milling. After drying, a secondary powder was obtained, in which the calcining aid included 0.01 mol TiO2, 0.005 mol Al2O3, and 0.024 mol SiO2.

[0111] After the secondary powder is ball-milled twice, 20wt% of a polyvinyl alcohol solution with a mass fraction of 8% and 0.5wt% of glycerol are slowly added. During the addition process, the powder is continuously ground and the granules are screened with 40-mesh and 200-mesh sieves to obtain mixed granules.

[0112] The above-obtained mixed granules were sealed and aged for 24 hours before being pressed into tablets. First, a certain amount of the aged mixed granules was weighed and placed into a mold, then pressed to 7.5 MPa and held for 5 minutes to obtain a green sheet with a diameter of 20 mm and a thickness of 2 mm.

[0113] The green body is placed in an air-atmosphere tube furnace for debinding and sintering. To remove polyvinyl alcohol from the green body, the temperature is increased from room temperature to 400°C at a rate of 1.5°C / min and held for 30 minutes to ensure complete debinding. Then, the temperature is increased to 1150°C at a rate of 2.5°C / min, and then to 1350°C at a rate of 10°C / min and held for 3 hours. Then, the temperature is decreased to 1150°C at a rate of 10°C / min, and then to 500°C at a rate of 1.5°C / min. Finally, the furnace is cooled to room temperature to obtain barium titanate-based PTC ceramic material.

[0114] The XRD pattern of the prepared barium titanate-based PTC ceramic material at room temperature is as follows: Figure 2 As shown in (e), the SEM image of the barium titanate-based PTC ceramic material is as follows: Figure 3 As shown in (a) above, the Curie temperature, room temperature resistivity, and relative density can be referenced from [reference]. Figure 4 , Figure 5 and Figure 6 .

[0115] The performance of the barium titanate-based PTC ceramic samples prepared in the above embodiments and comparative examples was tested, and the test results are as follows: Figures 2 to 6 .

[0116] in, Figure 2 The XRD patterns of the barium titanate-based PTC ceramic materials prepared in Examples 1-4 and Comparative Example 1 at room temperature are shown. By fitting and comparing the patterns with the JCPDS database (PDF#44-0093) using JADE software, it can be confirmed that the PTC ceramic samples prepared in Examples 1-4 and Comparative Example 1 all have a P4mm(99) tetragonal perovskite structure, indicating that Y element has diffused into the crystal lattice to form a solid solution. As can be seen from the figures, the XRD diffraction peaks of different Y2O3 samples at room temperature are sharp, indicating that the prepared PTC ceramics have relatively good crystallinity.

[0117] Figure 3 The images show SEM images of the barium titanate-based PTC ceramic samples prepared in Examples 1-4 and Comparative Example 1. The images show that Y₂O₃ significantly affects the microstructure of the ceramics. With increasing Y₂O₃ content, Y segregation at grain boundaries inhibits grain boundary migration, leading to gradually smaller and more uniform grain sizes, and an increase in the number of grain boundaries. Grain size can affect the Curie temperature of the material; when the grain size decreases to a certain extent, the size effect causes a decrease in the Curie temperature. An increase in grain boundaries affects the room-temperature resistivity of the material. Since the resistivity of grains is relatively small compared to grain boundaries, a high proportion of grain boundaries will increase the overall resistivity of the material.

[0118] Figure 4 , Figure 5 The figures show the Curie temperature and room-temperature resistivity of barium titanate-based PTC ceramics prepared in Examples 1-4 and Comparative Example 1, respectively, as a function of Y₂O₃ doping concentration. As can be seen from the figures, the Curie temperatures of the PTC ceramics prepared in the four examples are all between 30℃ and 85℃, and the room-temperature resistivity is on the order of 10⁻⁶. 5 ~10 7 The order of magnitude difference indicates that the preparation method of the present invention achieves a synergistic design of low Curie temperature and high room temperature resistivity for barium titanate-based PTC ceramics.

[0119] Figure 6 The graphs show the relative density of barium titanate-based PTC ceramics prepared in Examples 1-4 and Comparative Example 1 as a function of Y₂O₃ doping concentration. As can be seen from the graphs, the relative density of the PTC ceramics prepared in the four examples is all above 92%. This indicates that the PTC ceramic material prepared by this invention maintains good application performance while lowering the Curie temperature and increasing the room-temperature resistivity.

[0120] The terms "first" and "second" used in this document are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature marked "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0121] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0122] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. A method of producing barium titanate-based PTC ceramics, characterized by, The method comprises the following steps: weighing primary raw materials, the primary raw materials comprising BaCO3, TiO2, SrCO3 and Y2O3; sequentially subjecting the primary raw materials to primary ball milling and primary drying to obtain primary powder; subjecting the primary powder to calcination to obtain calcined materials; mixing the calcined materials and a sintering aid, and sequentially subjecting the mixture to secondary ball milling and secondary drying to obtain secondary powder; mixing the secondary powder with a binder and a lubricant to obtain mixed granules; subjecting the mixed granules to tabletting to obtain green bodies; The green body is subjected to glue removal sintering to obtain the barium titanate-based PTC ceramic, wherein the Curie temperature of the barium titanate-based PTC ceramic is 0-90 DEG C, and the order of magnitude of the room temperature resistivity is 10 5 ~10 8 Ω·cm, the primary raw materials comprise, in terms of molar fractions, 0.1-1 parts of BaCO3, 0.1-1 parts of SrCO3, 0.2-1.5 parts of TiO2 and 0.0001-0.005 parts of Y2O3, in the primary raw materials, the molar amount of titanium atoms is equal to the sum of the molar amounts of barium atoms and strontium atoms, the sintering aid comprises 0.001-0.01 parts of Al2O3, 0.01-0.05 parts of SiO2 and 0.003-0.015 parts of TiO2.

2. The method of claim 1, wherein, the primary ball milling satisfies at least one of the following conditions: the mass ratio of the first grinding medium to the primary raw materials is (1-3):1; the mass ratio of the first ball milling dispersion medium to the primary raw materials is (1-3):1; the rotation speed of the primary ball milling is 200-250 r / min; the ball milling time is 15-30 h, and the ball milling is performed for 10-30 min with an intermittent time of 1-5 min, and the mode of the primary ball milling is set to positive and negative rotation alternately, optionally, the temperature of the primary drying is 50-80℃, and the time is 3-12 h.

3. The method of claim 1, wherein, the temperature of the calcination is 1100-1250℃, and the holding time is 1-4 h.

4. The method of claim 1, wherein, the secondary ball milling satisfies at least one of the following conditions: the mass ratio of the second grinding medium to the calcined materials is (1-3):1; the mass ratio of the second ball milling dispersion medium to the calcined materials is (1-3):1; the rotation speed of the secondary ball milling is 200-250 r / min; the ball milling time is 15-30 h, and the ball milling is performed for 10-30 min with an intermittent time of 1-5 min, and the mode of the secondary ball milling is set to positive and negative rotation alternately, optionally, the temperature of the secondary drying is 50-80℃, and the time is 3-12 h.

5. The method of claim 1, wherein, the mixed granules satisfy at least one of the following conditions: the binder comprises at least one of polyvinyl alcohol solution, phenolic resin solution, epoxy resin solution and vinyl butyral solution; the lubricant comprises at least one of glycerol, calcium stearate and magnesium stearate; based on the total mass of the mixed granules, the mass fraction of the lubricant is 0.1%-1%, the mass fraction of the binder is 14.9%-24%, and the mass fraction of the secondary powder is 75%-85%; the mixed granules are further subjected to grinding and sieving treatment, and the mesh number of the sieving screen is 20-60 mesh and 100-300 mesh.

6. The method of claim 1, wherein, the pressure of the tabletting is 5-10 MPa, and the holding time is 1-10 min; Optionally, before the tabletting, the mixed granules are pretreated by placing the mixed granules in a sealed environment for 10h-48h.

7. The method of claim 1, wherein, The de-binding sintering comprises: gradually increasing the green body from room temperature to a de-binding temperature of 200-900℃ at a rate of 0.4-4.0℃ / min, and maintaining the temperature for 10-60min; increasing the de-binding temperature to an intermediate temperature of 1000-1250℃ at a rate of 1-10℃ / min; increasing the intermediate temperature to a sintering temperature of 1250-1500℃ at a rate of 2-16℃ / min, and maintaining the temperature for 1-5h; decreasing the sintering temperature to the intermediate temperature at a rate of 2-16℃ / min; cooling the intermediate temperature to room temperature with the furnace.

8. A barium titanate-based PTC ceramic, characterized by, the barium titanate-based PTC ceramic prepared by the method of any one of claims 1-7, Optionally, the barium titanate-based PTC ceramic further satisfies at least one of the following conditions: the barium titanate-based PTC ceramic is pseudo-tetragonal phase; the barium titanate-based PTC ceramic has a grain size of 1-30μm; the barium titanate-based PTC ceramic has a relative density of 90-99%.

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