A large current flow pressure sensitive resistor sheet and a preparation method thereof

Abstract

The application discloses a large current flow pressure sensitive resistor sheet and a preparation method thereof, and belongs to the technical field of pressure sensitive resistors. Raw materials of the pressure sensitive resistor sheet include modified ZnO 93-96 mol%, Bi2O3 1.2-1.6 mol%, Co3O4 0.5-1.5 mol%, Mn2O3 0.3-0.8 mol%, Sb2O3 1.0-3.0 mol%, NiO 0.3-0.8 mol% and Li2CO3 0.05-0.3 mol%. A silane coupling agent with a quaternary ammonium fluoride structure is used to modify the surface of ZnO. The quaternary ammonium fluoride structure increases the isoelectric point of ZnO, so that the ZnO is positively charged at a higher pH, the interaction with an anionic dispersant is enhanced, and the effect of the anionic dispersant on the slurry is improved. F is uniformly dispersed on the surface of ZnO by the silane coupling agent. Li is used as a diffusion carrier during subsequent sintering. The synergistic effect of Li and F can improve the mobility of F in the crystal lattice, and the introduction of Li and F can enhance the properties of the ZnO pressure sensitive resistor. ‑ + + ‑ ‑ + ‑ ​​​​​​​

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of voltage-dependent resistors, and particularly relates to a large-current voltage-dependent resistor and a preparation method thereof. BACKGROUND

[0002] ZnO voltage-dependent resistor is a new type of multifunctional semiconductor ceramic element which is sintered by using traditional ceramic process and taking ZnO as main raw material and doping a small amount of other metal oxides (Bi2O3, Sb2O3, Co3O4, Ni2O3, SiO2, etc.). The ZnO voltage-dependent resistor can be widely applied in high-voltage and low-voltage power systems, rail transit, facility protection and other fields due to the advantages of cheap raw materials, simple process, adjustable potential gradient, high non-linear coefficient, low voltage ratio, long running time in the circuit, etc. The large-current ZnO voltage-dependent resistor is smaller in size, saves raw material cost, is more convenient in transportation and use, and is small in size, which conforms to the current development trend. At present, the trend of preparing high-gradient non-linear resistor is to dope rare earth oxides. Compared with other ordinary metal oxides, the rare earth oxides are more expensive, and the high-quality high-gradient resistor sheets on the market are basically monopolized by foreign countries, and the high price becomes a key restricting factor. However, excellent non-linear resistor performance can be finally obtained by optimizing the formula and process.

[0003] The key technology of preparing ZnO voltage-dependent resistor lies in the formula and the uniformity of the ceramic body. The uniformity of the ceramic body directly affects the electrical performance of the finished product. In the formula of the ZnO voltage-dependent resistor, the doping mainly includes donor doping and acceptor doping. The donor doping can be divided into rare earth element doping and transition metal oxide doping, and the acceptor doping mainly includes monovalent ions such as Li + , Na + , K + , Ag + , etc. Among them, the radius of lithium ion is slightly smaller than that of zinc ion, the lithium ion enters the ZnO crystal lattice, changes the electrical parameters of the grain and the grain boundary, and a small amount of Li + doping can improve the non-linear coefficient and leakage. At present, there are still few reports on fluorine ions as anion doping zinc oxide, mainly due to the dispersion of fluorine ions and the influence on other doped oxides. Good dispersion of the slurry is a key factor to obtain a dense body, uniform microstructure and additive distribution, and the smallest defects, and finally obtain excellent non-linear resistor. Among them, the content of the dispersant is a key factor to make the slurry have good fluidity and dispersity. SUMMARY

[0004] The application provides a large-current voltage-dependent resistor and a preparation method thereof. A silane coupling agent with a quaternary ammonium fluoride structure is used to modify the surface of ZnO, so that more positive charges and F -, the quaternary ammonium salt structure improves the isoelectric point of ZnO, so that it also has more positive charges at a higher pH, enhances the interaction with anionic dispersants, and enhances the dispersion stability of the slurry by anionic dispersants; F - uniformly disperses on the surface of ZnO, and in subsequent sintering, Li + acts as a diffusion carrier, Li + and F - synergistically improve the mobility of F - in the crystal lattice, and the introduction of Li + and F - enhances the properties of ZnO varistors.

[0005] The technical solution for achieving the purpose of the present application is as follows: a preparation method of a large-current varistor disc, comprising the following steps:

[0006] S1. ZnO surface modification: adding ZnO into a solution containing deionized water and ethanol, adding a silane coupling agent with a fluorinated quaternary ammonium salt structure, and stirring to obtain modified ZnO;

[0007] S2. configuring raw materials for preparing a varistor disc: modified ZnO 93-96 mol%, Bi2O3 1.2-1.6 mol%, Co3O4 0.5-1.5 mol%, Mn2O3 0.3-0.8 mol%, Sb2O3 1.0-3.0 mol%, NiO 0.3-0.8 mol%, and Li2CO3 0.05-0.3 mol%;

[0008] S3. mixing the additives except for modified ZnO and Li2CO3, adding deionized water and an anionic dispersant to prepare an additive slurry, sanding, drying and crushing to obtain an additive powder, mixing ZnO, Li2CO3 and the additive powder, adding deionized water, an anionic dispersant and a binder, and ball milling in a ball mill to obtain a total slurry;

[0009] S4. performing spray granulation, water-containing aging and dry pressing on the total slurry, performing degassing treatment on the green body obtained by dry pressing, then high-temperature sintering, heat treatment after grinding and flattening, coating silver electrodes on the upper and lower end faces, and coating insulating glaze on the side face to obtain a varistor;

[0010] The degassing treatment operation is as follows:

[0011] under an inert atmosphere, placing the green body into a closed system at a temperature of 150 ℃, heating to 300 ℃ at a speed of 2-5 ℃ / min, treating for 0.5-1 h after keeping warm, then opening the system, and treating at 300-450 ℃ for 1-2 h;

[0012] The structure of the silane coupling agent with a fluorinated quaternary ammonium salt structure is as follows:

[0013] ; wherein R1, R2, R3, R4, R5 and R6 are at least one of methyl and ethyl.

[0014] The mechanism of the present application is mainly as shown in the attached Figure 1 figure, the surface of zinc oxide is modified by silane coupling agent with fluorinated quaternary ammonium salt structure, cationic groups are additionally introduced to improve the interaction with anions, and F - is uniformly dispersed on the surface of ZnO, the quaternary ammonium salt structure is slowly decomposed at 200-500 degrees Celsius, F - reacts with Li + to form LiF or ZnF2 on the surface of ZnO, and as the temperature rises, F - reacts with Li + enters the ZnO lattice, changing the electrical parameters of the grain and grain boundary.

[0015] Preferably, in step S1, the ratio of water to ethanol is 1:3-1:5, the mass ratio of silane coupling agent to ZnO is (0.3-0.8):(99.2-99.7), the reaction temperature is 30-60 ℃, and the reaction time is at least 1 h.

[0016] Preferably, in step S3, the solid content of the additive slurry is 20-50 wt.%, the amount of anionic dispersant added to the additive powder is 0.1-1 wt.% of the additive, the particle size of the mixed slurry is 400-600 nm after sanding; the amount of anionic dispersant used in the total slurry is 0.1-1 wt.% of the total mass of the powder, the amount of binder used is 0.5-1 wt.% of the total mass of the powder, and the ball milling time is 20-24 h; the binder is polyvinyl alcohol, and the anionic dispersant is an ammonium polyacrylate dispersant.

[0017] Preferably, in step S4, the water-containing aging is a water content test on the powder after granulation, and the water content is adjusted according to the test results to make the water content of the powder after granulation 1.2-2%.

[0018] Preferably, in step S4, the high-temperature sintering step is to raise the temperature to 800-900 ℃ at a temperature rising rate of 1.5-2.0 ℃ / min, then to 1000-1200 ℃ at a temperature rising rate of 0.5-1.0 ℃ / min, and then to cool down with the furnace after holding for 1.5-2.5 h; the heat treatment temperature is 400-600 ℃, and the time is 1-2 h.

[0019] Preferably, the preparation method of the silane coupling agent with fluorinated quaternary ammonium salt structure is as follows:

[0020] Disperse 1 eq of ammonium salt silane coupling agent and at least 5 eq of potassium fluoride in methanol, stir at 20-30 °C for 40-80 min, filter to remove solids, remove most of the solvent by rotary evaporation, add dichloromethane, wash the organic phase with deionized water to remove solvent and obtain fluorinated quaternary ammonium salt silane coupling agent.

[0021] The ammonium salt silane coupling agent is one or more of 3-triethoxysilylpropyltrimethyl chloride, 3-triethoxysilylpropyltrimethyl bromide, 3-triethoxysilylpropyltriethyl chloride, 3-triethoxysilylpropyltriethyl bromide, 3-trimethoxysilylpropyltrimethyl chloride, 3-trimethoxysilylpropyltrimethyl bromide, 3-trimethoxysilylpropyltriethyl chloride, and 3-trimethoxysilylpropyltriethyl bromide.

[0022] Preferably, the ammonium salt silane coupling agent is 3-triethoxysilylpropyltrimethylchloro.

[0023] The present invention also discloses a high-current varistor, which is obtained by the above-described method for preparing a high-current varistor.

[0024] Beneficial effects

[0025] This invention offers the following advantages: it provides a high-current varistor and its preparation method, wherein the varistor slurry has low viscosity and good dispersibility; by modifying zinc oxide with a silane coupling agent, a quaternary ammonium salt cation with low pH sensitivity is first introduced, improving the interaction with the anionic dispersant; secondly, the uniformly dispersed introduction of F... - To the ZnO surface without affecting other dopants; trace amounts of Li + Doping improves the nonlinear coefficient and leakage current while increasing F. - Mobility in the crystal lattice; introduction of F - It plays a role in inhibiting grain growth, resulting in finer and more uniform grains; F - Replace O 2- It can alter the grain boundary charge distribution, increase the barrier height, improve the nonlinear coefficient, and reduce leakage current; appropriate amounts of F - The incorporation of [a substance] can stabilize the crystal structure, reduce the generation of oxygen vacancies at high temperatures, thereby delaying material aging and extending device lifespan. Attached Figure Description

[0026] Figure 1 The modification steps of quaternized ammonium silane coupling agents on ZnO surface and their interaction mechanism with anionic dispersants are investigated. Detailed Implementation

[0027] The technical solutions in the embodiments of the present application will be clearly and completely described below with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments of the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0028] In the embodiments, the experimental methods used are conventional methods, and the materials, reagents, etc. used are commercially available unless otherwise specified.

[0029] The raw materials and equipment used in the embodiments and comparative examples are described as follows:

[0030] 3-triethoxysilylpropyl trimethyl chloride: Rohn reagent;

[0031] Potassium fluoride: ≥99.97%, Shanghai Aladdin;

[0032] ZnO: pressure-sensitive grade, Nantong Jinqi Chemical Co., Ltd.;

[0033] Bi2O3: electronic grade, Shanghai Jiujia Powder Material Co., Ltd.;

[0034] Sb2O3: electronic grade, Chengdu Dayu Functional Material Co., Ltd.;

[0035] Mn2O3: electronic grade, Chengdu Dayu Functional Material Co., Ltd.;

[0036] Co3O4: electronic grade, Shanghai Jiujia Powder Material Co., Ltd.;

[0037] NiO: electronic grade, Shanghai Jiujia Powder Material Co., Ltd.;

[0038] Polyvinyl alcohol: PVA-1788, industrial grade, Shanghai Petrochemical Co., Ltd.;

[0039] Release agent: HDA-80 type ceramic lubricant, Xi'an Xinxing Electronic Material Co., Ltd.;

[0040] Anionic dispersant: D-134 dispersant, Japan First Industrial Pharmaceutical;

[0041] 3-aminopropyl triethoxysilane: Shanghai Aladdin;

[0042] Li2CO3: 99.999 %, Rohn reagent;

[0043] LiF: 99.99 %, Rohn reagent.

[0044] Silane coupling agent 1

[0045] The 1 eq of 3-triethoxysilylpropyl trimethyl chloride and 15 eq of potassium fluoride were dispersed in methanol, stirred at 30 °C for 60 min, the solid was removed by filtration, after removing most of the solvent by rotary evaporation, dichloromethane was added, the organic phase was washed with deionized water, and the silane coupling agent 1 was obtained by removing the solvent.

[0046] Silane coupling agent 2

[0047] 3-triethoxysilylpropyl trimethyl chloride was used.

[0048] Silane coupling agent 3

[0049] 3-aminopropyl triethoxysilane was used.

[0050] Example 1

[0051] S1. ZnO surface modification: 997 g of ZnO was added to a solution containing deionized water and ethanol, the volume ratio of deionized water and ethanol was 1:3, 3 g of silane coupling agent 1 was added, stirred at 40 °C for 2 h, and quaternary ammonium modified ZnO was obtained;

[0052] S2. Preparation of raw materials for pressure sensitive resistor sheet: modified ZnO 94.60 mol%, Bi2O3 1.45 mol%, Co3O4 0.55 mol%, Mn2O3 0.51 mol%, Sb2O3 2.10 mol%, NiO 0.52 mol%, and Li2CO3 0.27 mol%;

[0053] S3. The additives except for modified ZnO and Li2CO3 were mixed, and a slurry containing 20 wt.% of additives was prepared by adding deionized water and anionic dispersant, the amount of anionic dispersant added was 0.4 wt.% of the total mass of the powder, the mixed slurry was sand milled by using a NETZSCH ZETA® horizontal sand mill at a main machine speed of 1000 rpm, a feed pump speed of 30 rpm, and a circulation of once, until the particle size of the mixed slurry was 500 nm, after sand milling, drying and crushing were performed to obtain the additive powder, then ZnO, Li2CO3 and the additive powder were mixed, deionized water, anionic dispersant and binder were added and mixed in a polyurethane ball mill tank, the amount of anionic dispersant was 0.4 wt.% of the total mass of the powder, the amount of binder was 0.8 wt.% of the total mass of the powder, and the grinding medium was agate ball (powder: deionized water: agate ball = 1:0.65:2.4), the ball mill (GMJ-8-5, Wuxi Hengguang Powder Equipment Co., Ltd.) was used for 24 h ball milling refinement treatment at a speed of 400 r / min, and the total slurry was obtained.

[0054] S4. The total slurry is spray granulated using an industrial grade high-speed centrifugal spray dryer, with an inlet air temperature of 220 ℃, an outlet air temperature of 110 ℃, and an atomizer rotation speed of 40 Hz; the powder after spray granulation is tested for actual moisture content, and with the powder moisture content of 1.6 wt.% as the target, a certain amount of deionized water is added to increase the moisture content, and 0.7 wt.% of a release agent based on the mass of the powder is added to facilitate dry pressing of the powder; after mixing, the mixture is uniformly sprayed on the powder, and the mixture is sealed and allowed to stand for 20 h; dry pressing: a bidirectional powder hydraulic press (Y79-25, Shanghai Hucheng Electric Co., Ltd.) is used for dry pressing, and the density of the circular green body obtained by pressing is 3.20 g / cm 3 After the green body is dried, the green body is subjected to debinding treatment: in an inert atmosphere, a closed system, at a temperature of 150 ℃, the green body is placed in the closed system, and the system is heated to 300 ℃ at a rate of 2-5 ℃ / min, and after 1 h of heat preservation, the system is opened, and the green body is treated at 450 ℃ for 2 h; then high-temperature sintering: using a muffle furnace at 1100 ℃ for high-temperature sintering, heat preservation for 1 h; after grinding and flattening, heat treatment (heat preservation at 550 ℃ for 180 min), silver electrodes are coated on the upper and lower end faces, and insulating glaze is coated on the side face, to obtain a varistor.

[0055] Example 2

[0056] Compared with the preparation method of Example 1, the difference is that in step S1, 997 g of ZnO is replaced by 995 g of ZnO, and 3 g of silane coupling agent 1 is replaced by 5 g of silane coupling agent 1.

[0057] Example 3

[0058] Compared with the preparation method of Example 1, the difference is that in step S1, 997 g of ZnO is replaced by 992 g of ZnO, and 3 g of silane coupling agent 1 is replaced by 8 g of silane coupling agent 1.

[0059] Comparative Example 1

[0060] Compared with the preparation method of Example 1, the difference is that the surface modification of ZnO in step S1 is not performed, and the modified ZnO in step S2 is replaced by ZnO.

[0061] Comparative Example 2

[0062] Compared with the preparation method of Example 1, the difference is that in step S1, 3 g of silane coupling agent 1 is replaced by 3 g of silane coupling agent 2.

[0063] Comparative Example 3

[0064] Compared with the preparation method of Example 1, the difference is that in step S1, 3 g of silane coupling agent 1 is replaced by 3 g of silane coupling agent 3.

[0065] Comparative Example 4

[0066] Compared with the preparation method of Example 1, the difference is that in step S1, 997 g of ZnO is replaced by 985 g of ZnO, and 3 g of silane coupling agent 1 is replaced by 15 g of silane coupling agent 1.

[0067] Comparative Example 5

[0068] Compared with the preparation method of Example 1, the difference is that in steps S2 and S3, 0.27 mol% of Li2CO3 is replaced by 0.27 mol% of modified ZnO.

[0069] Comparative Example 6

[0070] Compared with the preparation method of Example 1, the difference is that the ZnO surface modification of step S1 is not performed, the modified ZnO of step S2 is replaced by ZnO, and in steps S2 and S3, 0.27 mol% of Li2CO3 is replaced by 0.27 mol% of LiF.

[0071] The following is the test method of the performance parameters involved in the present application:

[0072] Total slurry viscosity: determined using a Shanghai Changji NDJ-8S rotary viscometer;

[0073] Grain size: SEM characterization of the upper surface of the resistor disc;

[0074] Nonlinear coefficient of ZnO varistor: α = 1 / log l0 (U 1mA / U 0.1mA ), wherein: α is the nonlinear coefficient; U 0.1mA is the voltage value of the varistor under direct current 0.1 mA, kV;

[0075] Residual voltage ratio: the resistor disc is tested by an impulse current tester for 8 / 20 μs lightning impulse current simulation test, and the residual voltage value U 5kA of the resistor disc after passing through 5 kA impulse current is measured, so as to calculate the residual voltage ratio, and the residual voltage ratio of the varistor is calculated: K 5kA = U 5kA / U 1mA , wherein: K 5kA is the residual voltage ratio under 5 kA lightning current; U 5kA is the residual voltage of the varistor passing through 8 / 20 μs;

[0076] Aging coefficient: the resistor disc is tested by an AC / DC aging machine for accelerated aging test, and the test condition is 135 ℃, 85% U 1mA voltage for continuous operation for 96 h, and the aging coefficient K ct is measured. 96 h power, 1 h power, K ct The smaller, the better the aging resistance.

[0077] Table 1 Total slurry viscosity and electrical properties of the varistor

[0078]

[0079] From the performance test of the examples and comparative examples, it can be seen that, within a suitable range, the surface of ZnO is modified by using a silane coupling agent with a fluorinated quaternary ammonium salt structure, and a varistor with excellent performance can be obtained.

[0080] From the data of examples 1-3 and comparative example 4 in table 1, it can be seen that, as the amount of the silane coupling agent with a fluorinated quaternary ammonium salt structure for modifying ZnO increases, the total slurry viscosity gradually decreases, but the electrical properties first increase and then decrease. The gradual decrease in the total slurry viscosity is due to the introduction of more cationic groups, and the reason for the first increase and then decrease in the electrical properties may be that 1) too much F - will cause too many defects; 2) poor dispersibility and uneven dispersion; 3) the probability of reaction with other dopants increases. From the data of comparative example 2, it can be seen that, by using a silane coupling agent with a chlorinated quaternary ammonium structure, the total slurry viscosity is close to that of example 1, but the electrical properties are not as good as those of examples 1-3, indicating that F - has a better effect on the electrical properties of the varistor than Cl - . From the data of comparative example 3, it can be seen that, by not using a silane coupling agent with a quaternary ammonium salt structure, the total slurry viscosity and the electrical properties are not as good as those of examples 1-3. From the data of comparative example 5, it can be seen that, by not adding Li2CO3, the performance of the total slurry viscosity is less affected, but the electrical properties of the varistor are greatly affected, resulting in a performance that is not as good as that of the examples; from the data of comparative example 6, it can be seen that, by directly adding LiF, the total slurry viscosity and the electrical properties of the varistor will decrease, proving that the dispersibility of LiF in the slurry has a great influence on the electrical properties of the varistor.

[0081] The preferred embodiments of the present application disclosed above are only used to help explain the present application. The preferred embodiments do not describe all the details and limit the present application to the specific embodiments described. Obviously, many modifications and variations can be made according to the content of the present application. The present application is selected and specifically described in order to better explain the principles and practical applications of the present application, so that those skilled in the art can well understand and utilize the present application. The present application is limited only by the claims and their full scope and equivalents.

Claims

1. A method for preparing a high-current varistor, characterized in that, Includes the following steps: S1. ZnO surface modification: ZnO is added to a solution containing deionized water and ethanol, a silane coupling agent with a fluorinated quaternary ammonium salt structure is added, and the mixture is stirred to obtain modified ZnO; S2. Prepare the raw materials for the preparation of the varistor: modified ZnO 93~96 mol%, Bi2O3 1.2~1.6 mol%, Co3O4 0.5~1.5 mol%, Mn2O3 0.3~0.8 mol%, Sb2O3 1.0~3.0 mol%, NiO 0.3~0.8 mol%, and Li2CO3 0.05~0.3 mol%. S3. Mix the additives except for modified ZnO and Li2CO3, add deionized water and anionic dispersant to prepare an additive slurry, sand mill and dry and pulverize to obtain additive powder. Mix ZnO, Li2CO3 and additive powder, add deionized water, anionic dispersant and binder, ball mill in ball mill to refine to obtain total slurry. S4. The total slurry is spray-granulated, aged with water, and dry-pressed. The dry-pressed blank is debinded, then sintered at high temperature, ground smooth, and heat-treated. Silver electrodes are coated on the upper and lower end faces, and insulating glaze is coated on the side to obtain a varistor. The adhesive removal process is as follows: In an inert atmosphere, at a temperature of 150 ℃, after placing the billet in a closed system, the temperature is increased to 300 ℃ at a rate of 2~5 ℃ / min, and the temperature is held for 0.5~1 h. Then, in an open system, the billet is treated at 300~450 ℃ for 1~2 h. The structure of the fluorinated quaternary ammonium salt silane coupling agent is shown below: In the formula, R1, R2, R3, R4, R5 and R6 are at least one of methyl and ethyl.

2. The method for preparing a high-current varistor as described in claim 1, characterized in that, In step S1, the ratio of water to ethanol is 1:3 to 1:5, the mass ratio of silane coupling agent to ZnO is (0.3 to 0.8): (99.2 to 99.7), the reaction temperature is 30 to 60 °C, and the reaction time is at least 1 h.

3. The method for preparing a high-current varistor as described in claim 1, characterized in that, In step S3, the solid content of the additive slurry is 20-50 wt.%, the amount of anionic dispersant added to the additive powder is 0.1-1 wt.% of the additive, and the mixture is milled until the particle size of the mixed slurry is 400-600 nm; the amount of anionic dispersant in the total slurry is 0.1-1 wt.% of the total mass of the powder, the amount of binder is 0.5-1 wt.% of the total mass of the powder, and the ball milling time is 20-24 h. The binder is polyvinyl alcohol, and the anionic dispersant is ammonium polyacrylate dispersant.

4. The method for preparing a high-current varistor as described in claim 1, characterized in that, In step S4, the water content aging involves testing the moisture content of the granulated powder and adjusting the moisture content based on the measurement results to ensure that the moisture content of the granulated powder is between 1.2 and 2 wt.%.

5. The method for preparing a high-current varistor as described in claim 1, characterized in that, In step S4, the high-temperature sintering step involves heating to 800-900 ℃ at a heating rate of 1.5-2.0 ℃ / min, then heating to 1000-1200 ℃ at a heating rate of 0.5-1.0 ℃ / min, holding at that temperature for 1.5-2.5 h, and then cooling down in the furnace. The heat treatment temperature is 400-600 ℃, and the time is 1-2 h.

6. The method for preparing a high-current varistor as described in claim 1, characterized in that, The preparation method of the fluorinated quaternary ammonium salt structured silane coupling agent is as follows: 1 eq of ammonium salt silane coupling agent and at least 5 eq of potassium fluoride were dispersed in methanol, stirred at 20-30 °C for 40-80 min, filtered to remove solids, and most of the solvent was removed by rotary evaporation. Dichloromethane was added, and the organic phase was washed with deionized water to remove the solvent and obtain the fluorinated quaternary ammonium salt silane coupling agent. The ammonium salt silane coupling agent is one or more of 3-triethoxysilylpropyltrimethyl chloride, 3-triethoxysilylpropyltrimethyl bromide, 3-triethoxysilylpropyltriethyl chloride, 3-triethoxysilylpropyltriethyl bromide, 3-trimethoxysilylpropyltrimethyl chloride, 3-trimethoxysilylpropyltrimethyl bromide, 3-trimethoxysilylpropyltriethyl chloride, and 3-trimethoxysilylpropyltriethyl bromide.

7. A high-current varistor, characterized in that, It is obtained by the preparation method of a high-current varistor sheet according to any one of claims 1 to 6.

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