A multi-element titanate-based PTC ceramic material and a method for preparing the same

Abstract

This application relates to the field of PTC ceramic materials technology, specifically disclosing a multi-component titanate-based PTC ceramic material and its preparation method. The PTC ceramic material comprises 88.5-93.5 parts of main phase raw material, 4.0-6.0 parts of dopant, 1.5-3.0 parts of glass phase modifier, 1.0-1.5 parts of sintering aid, 2.5-4.0 parts of binder, and 0.5-1.5 parts of granulation aid. NMP in the binder enhances hydrogen bonding, while HAP improves support and enhances structural uniformity. Modified polyvinyl alcohol improves powder dispersibility, resulting in increased green body density and ensuring structural integrity and stability. This invention achieves simultaneous optimization of low resistivity and high resistivity ratio through multi-component substitution and multi-phase doping. The glass phase modifier pins grain boundaries and inhibits excessive grain growth, while the sintering aid increases ceramic density and improves powder flowability; both simultaneously enhance the processing performance of the finished product.

Description

Technical Field

[0001] This application relates to the field of PTC ceramic materials technology, specifically to a multi-component titanate-based PTC ceramic material and its preparation method. Background Technology

[0002] PTC ceramic materials (positive temperature coefficient thermistors) are semiconductor functional ceramics made from barium titanate as a matrix through doping modification and high-temperature sintering. Their core characteristic is a non-linear, rapid increase in resistance with increasing temperature, especially exhibiting a step-like abrupt change near the Curie temperature. They also possess unique functions such as self-limiting temperature, overcurrent protection, and isothermal heating. The main body is BaTiO3-based ceramic, doped with Sr... 2+ Pb 2+ It can precisely control the Curie temperature and incorporate La 3+ 、Nd 3+ Rare earth elements or oxides such as Nb2O5 and Ta2O5 can optimize room temperature resistance and PTC effect intensity, while adding a glass phase can improve grain boundary stability and reduce resistance drift during long-term use.

[0003] The preparation of PTC ceramics involves processes such as batching, ball milling, molding, high-temperature sintering, and electrode preparation. The finished product boasts advantages such as high pressure resistance, high temperature resistance, good thermal stability, long lifespan, no open flame, and water-electricity separation, making it widely used in home appliances, automobiles, new energy, and electronics. PTC ceramic materials use barium titanate-based ceramics as their core. Below the Curie temperature, the material has low resistance, allowing for smooth current conduction for heating or normal electrical conductivity. When the temperature rises to near the Curie temperature, the resistance increases sharply, causing a significant drop in circuit current and power, thus automatically limiting the temperature from rising further. In home appliance heating and automotive thermal management, this mechanism enables self-limiting temperature control, constant-temperature heating, and overheat protection. In electronic circuit protection, this characteristic is used to rapidly increase resistance during overcurrent or overheating, providing current limiting, overheat protection, and automatic recovery. The entire process relies on the material's own grain boundaries and ferroelectric-paraelectric phase transition for regulation, achieving integrated temperature control, heating, and protection without external control.

[0004] In protection circuit applications, reducing the startup power requires PTC protection elements to have low room temperature resistivity. To achieve the desired protection function—significantly increasing resistance over a narrow temperature range—the PTC protection element must possess both low room temperature resistivity and a high resistance-to-weight ratio. Existing technologies can reduce room temperature resistivity through doping, but achieving a synergistic optimization of low room temperature resistivity, high resistance-to-weight ratio, and a wide Curie temperature control range is difficult. Furthermore, the inorganic components in ceramic materials have poor bonding, requiring adhesive-assisted molding. The resulting sintered material is often brittle, making it difficult to maintain structural integrity.

[0005] Therefore, improving the overall performance of PTC materials while ensuring the optimization of both room temperature resistivity and resistance ratio is of great significance for their application in multiple fields. Summary of the Invention

[0006] In order to simultaneously achieve low room temperature resistivity and high resistance-to-weight ratio, as well as improve the integrity of PTC ceramics, this application provides a multi-component titanate-based PTC ceramic material and its preparation method.

[0007] This invention uses various titanates as the main phase raw materials, through Sr 2+ Ca 2+ Na + / Bi 3+ Right 2+ By performing A-site multi-substitution, barium titanate serves as the basic main phase to ensure the PTC effect. Strontium titanate and calcium titanate assist in regulating the Curie temperature while improving the ceramic density. Sodium bismuth titanate is introduced to optimize ferroelectric properties, thereby solving the problems of fixed Curie temperature and poor adaptability of traditional single titanates.

[0008] Niobium pentoxide and yttrium oxide serve as donor dopants, and manganese dioxide as acceptor dopants. The Nb content in niobium pentoxide and yttrium oxide... 5+ Y 3+ Replace Ti 4+ Achieving ceramic semiconductorization effectively reduces room temperature resistivity. Manganese dioxide introduces holes to optimize grain boundary barriers, improving the rise-resistivity ratio. This not only avoids performance imbalances caused by single doping but also achieves simultaneous optimization of low resistivity and high rise-resistivity ratio.

[0009] Glass phase modifiers form a composite glass phase that fills grain boundary pores, promotes the sintering of lead-free systems, and simultaneously pins grain boundaries and inhibits excessive grain growth, thereby improving both electrical stability and the mechanical strength of ceramics. Nano-alumina in the sintering aids utilizes high surface activity to lower the sintering temperature and increase ceramic density, while boron nitride improves powder flowability, aids in granulation and pressing, and enhances the processing performance of the finished product.

[0010] Donor doping with niobium pentoxide and yttrium oxide provides low-room-temperature conductivity. Furthermore, the introduction of the glassy phase acts as a grain boundary pinning agent, maintaining the integrity of the grain boundary structure. The binder system enhances the overall material density and introduces a strengthened residual stress field at the grain boundaries. These effects collectively achieve efficient overheat / overcurrent protection over a wide temperature range.

[0011] Furthermore, this invention obtains the adhesive by modifying polyvinyl alcohol and then mixing it with NMP and HAP. Under acid catalysis, the carboxyl groups in the modifier esterify with the hydroxyl groups in PVA, introducing alkyl steric hindrance groups into the polyvinyl alcohol molecular chain. This improves the uneven powder dispersion caused by PVA molecular chain entanglement, thereby effectively improving the dispersibility of inorganic phase powder materials, reducing agglomeration, making the ceramic material more uniformly mixed, reducing internal pores and microcracks, and increasing the density of the ceramic material, enabling it to better maintain structural integrity and stability in the final application. NMP enhances hydrogen bonding, improving powder compatibility and adhesion. HAP, through the supporting effect of the nanostructure, enhances cohesion and contributes to structural uniformity.

[0012] In a first aspect, the present invention provides a multi-component titanate-based PTC ceramic material, comprising 88.5-93.5 parts of main phase raw material, 4.0-6.0 parts of dopant, 1.5-3.0 parts of glass phase modifier, 1.0-1.5 parts of sintering aid, 2.5-4.0 parts of binder and 0.5-1.5 parts of granulation aid;

[0013] The method for preparing the adhesive includes the following steps:

[0014] Polyvinyl alcohol is added to water, heated to 70-80℃ and stirred to dissolve. Then p-toluenesulfonic acid is added and stirred evenly. Then 50wt% aqueous solution of modifier is added dropwise. Stir at 80-90℃ for 50-70 minutes. After cooling to 55-65℃, NMP and HAP are added and stirred for 10-30 minutes. Then ultrasonically disperse for 10-20 minutes and cool to room temperature to obtain the adhesive.

[0015] Furthermore, the main phase raw material is composed of barium titanate, strontium titanate, calcium titanate, and sodium bismuth titanate in a mass ratio of 80:5-8:3-5:2-3.

[0016] Furthermore, the dopant is composed of niobium pentoxide, yttrium oxide, and manganese dioxide in a mass ratio of 2:1-1.5:1.5-2.5.

[0017] Furthermore, the glass phase modifier is composed of silicon dioxide and aluminum oxide in a mass ratio of 1:0.7-1.5.

[0018] Furthermore, the sintering aid is composed of nano-alumina and boron nitride in a mass ratio of 0.5:0.7-1.2.

[0019] Furthermore, the mass ratio of the polyvinyl alcohol to water, p-toluenesulfonic acid, modifier, NMP, and HAP is 85:350-450:0.5-1:3-5:2-4:2-4.

[0020] Furthermore, the modifier is one of 2,2-dimethyl-3-hydroxypropionic acid, 2,2-dimethylbutyric acid, or 2-hydroxy-3-methylbutyric acid.

[0021] Furthermore, the granulation aid is diethylene glycol.

[0022] Secondly, this invention provides a method for preparing a multi-component titanate-based PTC ceramic material, comprising the following steps:

[0023] S1. Mix the main phase raw material, dopant, glass phase regulator and sintering aid to obtain powder material, wet ball mill for 30-35h to obtain slurry, then add binder and granulation aid and stir for 1-2h, spray granulate, and after granulation, press and form under 10-20MPa to obtain green body.

[0024] S2. The green body is heated to 600-700℃ at a rate of 2-3℃ / min and pre-fired in air for 1-2 hours. Then, it is heated to 1200-1300℃ at a rate of 200℃ / h in a reducing atmosphere with carbon powder and held for 30-60 minutes for reduction sintering. After cooling to room temperature, it is heated to 700-800℃ at a rate of 3-4℃ / min and held in air for 1.5-2.5 hours for re-oxidation sintering. After sintering, it is annealed at 800-900℃ for 5-6 hours and cooled to room temperature to obtain the multi-component titanate-based PTC ceramic material.

[0025] Furthermore, in the wet ball milling process, the mass ratio of powder material to balls and water is 1:1-1.5:1-1.5.

[0026] Compared with the prior art, the beneficial effects of this application are at least as follows:

[0027] 1. This invention utilizes Sr 2+ Ca 2+ Na + / Bi 3+ Right 2+ A-site multi-substitution is performed, with barium titanate as the basic host phase to ensure the PTC effect. Strontium titanate and calcium titanate assist in regulating the Curie temperature while improving ceramic density. Sodium bismuth titanate is introduced to optimize ferroelectric properties. Niobium pentoxide and yttrium oxide serve as donor dopants, and manganese dioxide as acceptor dopants. The Nb content in niobium pentoxide and yttrium oxide... 5+ Y 3+ Replace Ti 4+ Achieving ceramic semiconductorization effectively reduces room temperature resistivity.

[0028] 2. Glass phase modifiers form a composite glass phase that pins grain boundaries and inhibits excessive grain growth, thereby improving both electrical stability and the mechanical strength of the ceramic. Sintering aids lower the sintering temperature, increase the density of the ceramic, improve powder flowability, facilitate granulation and pressing, and enhance the processing performance of the finished product.

[0029] 3. NMP in the adhesive enhances hydrogen bonding and complexation, improving powder compatibility and adhesion. HAP, through the supporting effect of the nanostructure, enhances cohesion and contributes to structural uniformity. Modified polyvinyl alcohol addresses insufficient adhesion caused by molecular chain entanglement and its own hydroxyl group cohesion, improving powder dispersion and adhesion, and enhancing the molding and strength of ceramic materials. Detailed Implementation

[0030] The various embodiments or implementation schemes in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments.

[0031] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with an embodiment or example is included in at least one embodiment or example of this application. 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.

[0032] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0033] In this specification, unless otherwise specified, "parts" refers to "parts by weight".

[0034] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. 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 this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0035] NMP stands for N-methyl-2-pyrrolidone.

[0036] HAP is hydroxyapatite, needle-shaped, with a particle size of 20-30 nm.

[0037] Polyvinyl alcohol, with a degree of polymerization of 1700-1800 and a degree of alcoholysis of 88-89%.

[0038] Nano-alumina, particle size: 10-50nm.

[0039] Diethylene glycol, CAS No.: 110-99-6.

[0040] 2,2-Dimethyl-3-hydroxypropionic acid, CAS No.: 4835-90-9.

[0041] 2,2-Dimethylbutyric acid, CAS No.: 595-37-9.

[0042] 2-Hydroxy-3-methylbutyric acid, CAS No.: 4026-18-0.

[0043] Example 1

[0044] A method for preparing a multi-component titanate-based PTC ceramic material includes the following steps:

[0045] S1. Mix 80 parts of barium titanate, 6.5 parts of strontium titanate, 4 parts of calcium titanate, 2.5 parts of sodium bismuth titanate, 2 parts of niobium pentoxide, 1.25 parts of yttrium oxide, 2 parts of manganese dioxide, 1 part of silicon dioxide, 1.1 parts of aluminum oxide, 0.5 parts of nano-alumina, and 0.85 parts of boron nitride to obtain a powder material. Wet ball mill the powder material with balls and water at a mass ratio of 1:1.2:1.2 for 32 hours to obtain a slurry. Then add 4 parts of binder and 0.9 parts of diethylene glycol and stir for 1.5 hours. Spray granulate the mixture. After granulation, pressurize it at 15 MPa to obtain a green body.

[0046] S2. The green body is heated to 650℃ at 2.5℃ / min and pre-fired in air for 1.5h. Then, it is heated to 1250℃ at 200℃ / h in a reducing atmosphere with carbon powder and held for 45min for reduction sintering. After cooling to room temperature, it is heated to 750℃ at 3.5℃ / min and held in air for 2h for re-oxidation sintering. After sintering, it is annealed at 850℃ for 5h and cooled to room temperature to obtain multi-component titanate-based PTC ceramic material.

[0047] The method for preparing the adhesive includes the following steps:

[0048] Add 85 parts of polyvinyl alcohol to 400 parts of water, heat to 80°C and stir to dissolve. Then add 0.75 parts of p-toluenesulfonic acid and stir evenly. Then add 8 parts of 50wt% aqueous solution of 2,2-dimethyl-3-hydroxypropionic acid. Stir at 85°C for 60 minutes. Cool to 60°C and add 3 parts of NMP and 3 parts of HAP. Stir for 20 minutes and then ultrasonically disperse for 15 minutes. Cool to room temperature to obtain the adhesive.

[0049] Example 2

[0050] It is basically the same as Example 1, except that 2,2-dimethyl-3-hydroxypropionic acid is replaced with 2,2-dimethylbutyric acid.

[0051] Example 3

[0052] It is basically the same as Example 1, except that 2,2-dimethyl-3-hydroxypropionic acid is replaced with 2-hydroxy-3-methylbutyric acid.

[0053] Example 4

[0054] It is basically the same as Example 1, except that the aqueous solution of 50wt% 2,2-dimethyl-3-hydroxypropionic acid is 6 parts.

[0055] Example 5

[0056] It is basically the same as Example 1, except that the aqueous solution of 50wt% 2,2-dimethyl-3-hydroxypropionic acid is 10 parts.

[0057] Comparative Example 1

[0058] A method for preparing a multi-component titanate-based PTC ceramic material includes the following steps:

[0059] S1. Mix 80 parts of barium titanate, 6.5 parts of strontium titanate, 4 parts of calcium titanate, 2.5 parts of sodium bismuth titanate, 2 parts of niobium pentoxide, 1.25 parts of yttrium oxide, 2 parts of manganese dioxide, 1 part of silicon dioxide, 1.1 parts of aluminum oxide, 0.5 parts of nano-alumina, and 0.85 parts of boron nitride to obtain a powder material. Wet ball mill the powder material with balls and water at a mass ratio of 1:1.2:1.2 for 32 hours to obtain a slurry. Then add 4 parts of polyvinyl alcohol and 0.9 parts of diethylene glycol and stir for 1.5 hours. Spray granulate the mixture. After granulation, pressurize it at 15 MPa to obtain a green body.

[0060] S2. The green body is heated to 650℃ at 2.5℃ / min and pre-fired in air for 1.5h. Then, it is heated to 1250℃ at 200℃ / h in a reducing atmosphere with carbon powder and held for 45min for reduction sintering. After cooling to room temperature, it is heated to 750℃ at 3.5℃ / min and held in air for 2h for re-oxidation sintering. After sintering, it is annealed at 850℃ for 5h and cooled to room temperature to obtain multi-component titanate-based PTC ceramic material.

[0061] Comparative Example 2

[0062] It is basically the same as Example 1, except that 1 part of silicon dioxide and 1.1 parts of aluminum oxide are not added.

[0063] Comparative Example 3

[0064] It is basically the same as Example 1, except that 0.5 parts of nano-alumina and 0.85 parts of boron nitride are not added.

[0065] Comparative Example 4

[0066] It is basically the same as Example 1, except that NMP is not added to the adhesive.

[0067] Comparative Example 5

[0068] It is basically the same as Example 1, except that HAP is not added to the adhesive.

[0069] Comparative Example 6

[0070] A method for preparing a multi-component titanate-based PTC ceramic material includes the following steps:

[0071] S1. Mix 80 parts of barium titanate, 6.5 parts of strontium titanate, 4 parts of calcium titanate, 2.5 parts of sodium bismuth titanate, 2 parts of niobium pentoxide, 1.25 parts of yttrium oxide, 2 parts of manganese dioxide, 1 part of silicon dioxide, 1.1 parts of aluminum oxide, 0.5 parts of nano-alumina, and 0.85 parts of boron nitride to obtain a powder material. Wet ball mill the powder material with balls and water at a mass ratio of 1:1.2:1.2 for 32 hours to obtain a slurry. Then add 4 parts of binder and 0.9 parts of diethylene glycol and stir for 1.5 hours. Spray granulate the mixture. After granulation, pressurize it at 15 MPa to obtain a green body.

[0072] S2. The green body is heated to 650℃ at 2.5℃ / min and pre-fired in air for 1.5h. Then, it is heated to 1250℃ at 200℃ / h in a reducing atmosphere with carbon powder and held for 45min for reduction sintering. After cooling to room temperature, it is heated to 750℃ at 3.5℃ / min and held in air for 2h for re-oxidation sintering. After sintering, it is annealed at 850℃ for 5h and cooled to room temperature to obtain multi-component titanate-based PTC ceramic material.

[0073] The method for preparing the adhesive includes the following steps:

[0074] Add 85 parts of polyvinyl alcohol to 400 parts of water, heat to 80°C and stir to dissolve. Then add 0.75 parts of p-toluenesulfonic acid and stir evenly. Then add 8 parts of 50wt% propionic acid aqueous solution. Stir at 85°C for 60 minutes. Cool to 60°C and add 3 parts of NMP and 3 parts of HAP. Stir for 20 minutes and then ultrasonically disperse for 15 minutes. Cool to room temperature to obtain the adhesive.

[0075] Test section

[0076] 1. After grinding the PTC ceramic material prepared in the examples and comparative examples to a size of 24mm×15mm×2.5mm, chamfering, cleaning, drying, and then spraying aluminum electrodes on both sides to make a finished product, the resistivity-temperature curve of the product was tested.

[0077] The room temperature resistivity (resistivity measured at 25℃, denoted as ρ) was obtained based on the resistivity-temperature curve test. 25 ) and lift-to-drag ratio (I), I=lg(ρ) max / ρ min ), ρ max It is the maximum resistivity value of the finished product's resistivity-temperature curve, ρ. min It represents the minimum resistivity of the curve, and I is the resistance-to-weight ratio. The finished product was heated at a heating rate of 2℃ / min, and the measurement temperature range was 0-120℃.

[0078] 2. Cut the PTC ceramic material prepared in the examples and comparative examples into 30mm × 4mm × 3mm rectangular specimens. Place the ceramic specimens stably on two support points, start the testing machine, and slowly apply downward force with the loading head until the specimen breaks. Record the maximum load F at the time of fracture. Calculate the flexural strength σ using the formula: σ = 3FL / (2bh) 2 ); where L is the span of the fulcrum (20 mm), b is the width of the specimen (4 mm), and h is the thickness of the specimen (3 mm); unit MPa. Five identical specimens were prepared for each group, and the average value of the test results was taken.

[0079] Table 1

[0080]

[0081] As shown in Table 1, the PTC ceramic material in the examples simultaneously achieves low room temperature resistivity and high resistance-to-weight ratio, using various titanates as the main phase raw materials, and through Sr 2+ Ca 2+ Na + / Bi 3+ Right 2+A-site multi-substitution is performed, with barium titanate as the basic host phase to ensure the PTC effect. Strontium titanate and calcium titanate assist in regulating the Curie temperature while improving ceramic density. Sodium bismuth titanate is introduced to optimize ferroelectric properties. Niobium pentoxide and yttrium oxide serve as donor dopants, and manganese dioxide as acceptor dopants. The Nb content in niobium pentoxide and yttrium oxide... 5+ Y 3+ Replace Ti 4+ The ceramic semiconductor process effectively reduces room temperature resistivity. The combined effects of intrinsic barrier, physical pinning, and interfacial stress ensure that the resistivity of the material does not decrease when heated to 100°C, achieving a combined optimization of low resistivity and high up-resistivity ratio.

[0082] Compared to Comparative Example 1, in Comparative Example 1, polyvinyl alcohol binds the powders together through adhesion. However, PVA molecular chains are prone to entanglement and cohesion, leading to uneven powder dispersion and affecting the molding effect, resulting in lower flexural strength. After sintering, the ceramic exhibits increased porosity and grain boundary defects, extremely uneven donor and acceptor dispersion, and unstable grain boundary barriers, thus indirectly affecting resistivity and resistivity-to-weight ratio.

[0083] The embodiments demonstrate how modifying the adhesive effectively improves the flexural strength of ceramic materials, positively impacting room temperature resistivity and resistivity ratio. Modifying polyvinyl alcohol (PVA) and introducing alkyl steric hindrance groups effectively solves the PVA molecular chain entanglement problem, resulting in optimal dispersion of ceramic powder, uniform donor and acceptor doping, and stable grain boundary barriers. NMP enhances hydrogen bonding, improving powder compatibility and adhesion. HAP, through its nanostructure support, strengthens cohesion and contributes to structural uniformity.

[0084] Compared to Examples 2 and 3, Example 1 exhibits the highest flexural strength. This is likely due to the presence of a dimethyl quaternary carbon and a hydroxyl group in the 2,2-dimethyl-3-hydroxypropionic acid molecule, resulting in the strongest steric hindrance effect. The modified polyvinyl alcohol's side-chain hydroxyl groups can form hydrogen bonds with the ceramic powder, thereby improving compatibility and enhancing dispersion. The modifier in Example 2 lacks hydroxyl groups, and the steric hindrance effect in Example 3 is weaker than that in Example 1, leading to inferior dispersibility and compatibility compared to Example 1.

[0085] Compared with Examples 4 and 5, Example 1 has better performance, which indicates that the addition amount of Example 1 is the optimal one. At this time, the degree of esterification reaction of the modifier is moderate, which can effectively solve the entanglement of PVA molecular chains, ensure the fluidity of the binder, and result in uniform powder dispersion, high green compaction, optimal donor and acceptor doping efficiency, and stable grain boundary barrier.

[0086] Comparative Example 2 did not contain a glass phase modifier, and Comparative Example 3 did not contain a sintering aid. Compared to Example 1, the performance of both showed a significant decline. The glass phase modifier can pin grain boundaries, inhibit excessive grain growth, fill grain boundary pores, and improve ceramic density. Therefore, its absence leads to excessive grain growth, increased grain boundary defects, uneven donor-acceptor dispersion, unstable grain boundary barriers, and decreased ceramic density. Alumina and boron nitride, on the other hand, can improve powder flowability, promote uniform dispersion of donor-acceptor and glass phase, and improve green body density. Their absence results in poor powder flowability and uneven dispersion of donor-acceptor and glass phase. This demonstrates that both are indispensable in maintaining the performance of ceramic materials.

[0087] In Comparative Examples 4 and 5, the binders were not supplemented with NMP and HAP, respectively, and the performance of the ceramic materials decreased. This indicates that NMP enhances hydrogen bonding and improves powder compatibility, which can indirectly affect the improvement of material performance. HAP's supporting effect improves the uniformity of the structure and also has a certain effect on the density of the material. The combined effect of these two factors makes the material performance of Example 1 significantly better than that of Comparative Examples 4 and 5.

[0088] In Comparative Example 6, propionic acid was used to modify polyvinyl alcohol. Compared with Examples 1-3, the flexural strength of Comparative Example 6 was significantly lower. This indicates that the steric hindrance effect of the modifier is essential to solve the problem of molecular chain entanglement of polyvinyl alcohol. Propionic acid has no steric hindrance effect. It can improve the cohesion of polyvinyl alcohol rather than entanglement through modification. However, the dispersion effect of PVA after modification is far inferior to that of the examples.

[0089] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A multi-component titanate-based PTC ceramic material, characterized in that, It includes 88.5-93.5 parts of main phase raw material, 4.0-6.0 parts of dopant, 1.5-3.0 parts of glass phase modifier, 1.0-1.5 parts of sintering aid, 2.5-4.0 parts of binder and 0.5-1.5 parts of granulation aid; The method for preparing the adhesive includes the following steps: Polyvinyl alcohol is added to water, heated to 70-80℃ and stirred to dissolve. Then p-toluenesulfonic acid is added and stirred evenly. Then 50wt% aqueous solution of modifier is added dropwise. Stir at 80-90℃ for 50-70 minutes. After cooling to 55-65℃, NMP and HAP are added and stirred for 10-30 minutes. Then ultrasonically disperse for 10-20 minutes and cool to room temperature to obtain the adhesive. The main phase raw material is composed of barium titanate, strontium titanate, calcium titanate and sodium bismuth titanate in a mass ratio of 80:5-8:3-5:2-3; The dopant is composed of niobium pentoxide, yttrium oxide, and manganese dioxide in a mass ratio of 2:1-1.5:1.5-2.5; The sintering aid is composed of nano-alumina and boron nitride in a mass ratio of 0.5:0.7-1.2; The mass ratio of polyvinyl alcohol to water, p-toluenesulfonic acid, modifier, NMP, and HAP is 85:350-450:0.5-1:3-5:2-4:2-4; The modifier is one of 2,2-dimethyl-3-hydroxypropionic acid, 2,2-dimethylbutyric acid, or 2-hydroxy-3-methylbutyric acid.

2. The multi-component titanate-based PTC ceramic material as described in claim 1, characterized in that, The glass phase modifier is composed of silicon dioxide and aluminum oxide in a mass ratio of 1:0.7-1.

5.

3. The multi-component titanate-based PTC ceramic material as described in claim 1, characterized in that, The granulation aid is diethylene glycol.

4. The method for preparing the multi-component titanate-based PTC ceramic material according to any one of claims 1-3, characterized in that, Includes the following steps: S1. Mix the main phase raw material, dopant, glass phase regulator and sintering aid to obtain powder material, wet ball mill for 30-35h to obtain slurry, then add binder and granulation aid and stir for 1-2h, spray granulate, and after granulation, press and form under 10-20MPa to obtain green body. S2. The green body is heated to 600-700℃ at a rate of 2-3℃ / min and pre-fired in air for 1-2 hours. Then, it is heated to 1200-1300℃ at a rate of 200℃ / h in a reducing atmosphere with carbon powder and held for 30-60 minutes for reduction sintering. After cooling to room temperature, it is heated to 700-800℃ at a rate of 3-4℃ / min and held in air for 1.5-2.5 hours for re-oxidation sintering. After sintering, it is annealed at 800-900℃ for 5-6 hours and cooled to room temperature to obtain the multi-component titanate-based PTC ceramic material.

5. The method for preparing the multi-component titanate-based PTC ceramic material as described in claim 4, characterized in that, In the wet ball milling process, the mass ratio of powder material to balls and water is 1:1-1.5:1-1.5.

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