Preparation method of high-performance piezoresistor

Abstract

The invention discloses a preparation method of a high-performance piezoresistor, and relates to the technical field of electronics. The zinc oxide varistor is used for solving the problems that due to the fact that the response speed of an existing zinc oxide varistor is not high enough, the clamping voltage overshoot situation occurs, and rear-end equipment cannot be timely and effectively protected. Comprising the following steps: putting a mixture, zirconium balls, deionized water, an adhesive, a dispersing agent and a defoaming agent into a sand mill, and sanding for 4 hours to obtain a sanding material; the sand grinding material is subjected to spray granulation, obtained particles pass through a 80-mesh sieve and a 200-mesh sieve, granulated materials are obtained, and the granulated materials are pressed into blanks with set density; and the blank is sequentially subjected to glue discharging and pre-sintering, tunnel furnace sintering, cleaning, silver sintering, sheet inserting, welding and packaging, and the piezoresistor is obtained.

Description

Technical Field

[0001] The present invention relates to the field of electronic technology, and more particularly to a method for preparing a high-performance varistor. Background Art

[0002] Zinc oxide varistors are crucial protective components for power systems and electronic equipment. When the terminal voltage is below a certain threshold, the current flowing through the varistor is nearly zero. Above this threshold, the current increases dramatically as the terminal voltage increases, effectively protecting the system or equipment. In power systems, natural factors such as lightning can trigger overvoltages with high amplitudes and unusual waveforms, such as 10 / 350μs lightning waves. GB50057-2010, "Code for Design of Lightning Protection for Buildings," and other relevant standards impose strict requirements for lightning protection in power systems. This requires varistors to possess excellent 10 / 350μs performance to withstand lightning strikes and protect power equipment. During operation, electronic equipment may be subject to various surge voltages, such as those generated by power switching and lightning-induced surges. The 8 / 20μs waveform is a standard waveform for surge testing of electronic equipment. Improving the 8 / 20 performance of varistors can better suppress surge voltages and protect sensitive components in electronic equipment.

[0003] Currently commonly used zinc oxide varistors are electronic ceramics made of zinc oxide as the main material and doped with a variety of semiconductor materials (such as Bi2O3, Sb2O3, Co3O4, MnCO3, Ni2O3, Al(NO3)2·9H2O, etc.).

[0004] Commonly used zinc oxide varistors are composed of zinc oxide grains and grain boundaries. Under normal voltage, the grain boundaries exhibit high resistance, allowing only minimal leakage current to flow. When the voltage exceeds its threshold (varistor voltage), the potential barrier at the grain boundaries decreases, allowing a large number of electrons to traverse the boundaries, causing the resistance to drop sharply. This limits further voltage increases and provides overvoltage protection. The 10 / 350μs waveform has a relatively long rise time and duration, making it commonly used to simulate high-energy surges, such as strong lightning surges. Under a 10 / 350μs waveform, the varistor must withstand high energy for a prolonged period. This long duration generates significant heat within the varistor. If heat is not dissipated promptly, the grain boundary layer may undergo chemical decomposition or structural damage due to overheating, thus affecting its performance. The 8 / 20μs waveform has a faster rise time and shorter duration, making it commonly used to simulate general lightning-induced surges or switching overvoltages. Under this waveform, the varistor must respond quickly, limiting the overvoltage to a certain level within a short period of time. The fast rise time places high demands on the varistor's response speed. If the response speed is not fast enough, the clamping voltage may overshoot, and the back-end equipment cannot be protected in a timely and effective manner. Summary of the Invention

[0005] The embodiment of the present invention provides a method for preparing a high-performance varistor, which is used to solve the problem that the existing zinc oxide varistor has an insufficient response speed, an overshoot of the clamping voltage, and an inability to timely and effectively protect the back-end equipment.

[0006] An embodiment of the present invention provides a method for preparing a high-performance varistor, comprising:

[0007] ZnO:Bi2O3:Sb2O3:Co3O4:MnCO3:Ni2O3:Cu(NO3)2:H3BO3:AgNO3:Al(NO3)2·9H2O are mixed in the following ratios: 89.13%-91.11%:3.39%-4.15%:2.95%-3.61%:1.19%-1.45%:0.70%-0.86%:0.17%-0.21%:0.03%-0.05%:0.38%-0.46%:0.02%-0.04%:0.02%-0.04% to obtain a mixture, and the mixture, zirconium balls, deionized water, a binder, a dispersant, and a defoaming agent are put into a sand mill and sanded for 4 hours to obtain an abrasive;

[0008] Spray granulating the abrasive material, passing the obtained particles through an 80-mesh sieve and a 200-mesh sieve to obtain granules, and pressing the granules into blanks of a set density;

[0009] The blank is sequentially subjected to binder removal and pre-sintering, tunnel furnace sintering, cleaning, silver burning, sheet insertion, welding and encapsulation to obtain a varistor.

[0010] Preferably, the set density is 3.25g / m 3 -3.35g / m 3 .

[0011] Preferably, the blank is subjected to binder removal and pre-sintering in sequence, specifically comprising:

[0012] The blank is pre-sintered at 630°C for 8 hours to remove binder;

[0013] The tunnel furnace sintering specifically includes:

[0014] The debinding and pre-sintered blank is placed in a tunnel furnace for sintering at 1100-1200° C. for 25-30 hours and kept warm for 4 hours.

[0015] Preferably, the sintering temperature is 1185° C. and the holding time is 3 hours.

[0016] Preferably, before the mixture is put into a sand mill for sand grinding for 4 hours, the mixture, zirconium balls, deionized water, adhesive, dispersant and defoaming agent are mixed in a mass ratio of 1:1.5:1:0.12:0.1:0.1.

[0017] Preferably, the particle size of the granulated material is between 200 mesh and 80 mesh, and the moisture content is between 0.6 and 0.8.

[0018] In summary, the embodiment of the present invention provides a method for preparing a high-performance varistor, comprising: ZnO: Bi2O3: Sb2O3: Co3O4: MnCO3: Ni2O3: Cu(NO3)2: H3BO3: AgNO3: Al(NO3)2·9H2O in the following proportions: 89.13%-91.11%: 3.39%-4.15%: 2.95%-3.61%: 1.19%-1.45%: 0.70%-0.86%: 0.17%-0.21%: 0.03%-0 .05%: 0.38%-0.46%: 0.02%-0.04%: 0.02%-0.04% to obtain a mixture, the mixture is put into a sand mill with zirconium balls, deionized water, adhesive, dispersant, and defoaming agent for 4 hours to obtain abrasive; the abrasive is spray granulated, the obtained particles are passed through an 80-mesh sieve and a 200-mesh sieve to obtain granulated material, the granulated material is pressed into a blank of a set density; the blank is subjected to binder removal pre-sintering, tunnel furnace sintering, cleaning, silver burning, inserting, welding and encapsulation in sequence to obtain a varistor. Compared with the traditional zinc oxide varistor formula, in the embodiment of the present invention, Cu(NO3)2 is doped into the zinc oxide varistor formula. After adding Cu(NO3)2, copper ions (Cu 2+ ) radius (0.073nm) and Zn 2+ (0.074nm), easily entering the ZnO lattice or enriching at the grain boundary, forming a low-barrier interface; reducing the grain boundary barrier height, making it easier for electrons to cross the grain boundary, which is manifested macroscopically as a decrease in the varistor voltage, thereby causing a decrease in the voltage gradient (varistor voltage / thickness); at the same time, Cu(NO3)2 may inhibit ZnO grain growth, reduce grain size, increase the number of grain boundaries (reduced total grain boundary resistance), and further reduce the overall voltage gradient; this method not only improves the 8 / 20μs current-carrying capacity of the zinc oxide varistor, but also improves the 10 / 350μs current-carrying capacity. This solves the problem of existing zinc oxide varistors that have insufficient response speed, overshoot of the clamping voltage, and inability to effectively protect back-end equipment in a timely manner. DETAILED DESCRIPTION

[0019] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0020] An embodiment of the present invention provides a method for preparing a high-performance varistor, comprising:

[0021] Step 101: ZnO: Bi2O3: Sb2O3: Co3O4: MnCO3: Ni2O3: Cu(NO3)2: H3BO3: AgNO3: Al(NO3)2·9H2O are mixed in the following proportions: 89.13%-91.11%: 3.39%-4.15%: 2.95%-3.61%: 1.19%-1.45%: 0.70%-0.86%: 0.17%-0.21%: 0.03%-0.05%: 0.38%-0.46%: 0.02%-0.04%: 0.02%-0.04% to obtain a mixture; and the mixture, zirconium balls, deionized water, a binder, a dispersant, and a defoaming agent are placed in a sand mill and sanded for 4 hours to obtain an abrasive.

[0022] Step 102: spray granulating the abrasive material, passing the obtained particles through an 80-mesh sieve and a 200-mesh sieve to obtain granulated material, and pressing the granulated material into a blank of a set density;

[0023] Step 103 , sequentially subjecting the blank to binder removal and pre-sintering, tunnel furnace sintering, cleaning, silver burning, inserting, welding and encapsulation to obtain a varistor.

[0024] Specifically, in step 101, the materials are weighed according to the above principle, and the sum of the contents of each component is 100%. Then, the mixture, zirconium balls, deionized water, adhesive, dispersant, and defoaming agent are put into a sand mill and sanded for 4 hours to obtain abrasive.

[0025] In this method, ZnO is the main material, with a content ranging from 89.13% to 91.11%. ZnO has excellent nonlinear volt-ampere characteristics and is the basis for the varistor's voltage-sensitive function. The Bi2O3 content is 3.39% to 4.15%, which can reduce the sintering temperature, promote grain growth, and improve grain boundary characteristics, playing a significant role in improving the stability and reliability of the varistor. The Sb2O3 content is 2.95% to 3.61%, which can refine the grain size and enhance the nonlinear characteristics and energy absorption capacity of the varistor.

[0026] The Cu(NO3)2 content is between 0.03% and 0.05%. Doping Cu(NO3)2 into the zinc oxide varistor formula system can improve the 10 / 350μs and 8 / 20μs waveform impact capabilities of the zinc oxide varistor. It should be noted that in the embodiment of the present invention, the doping amount of Cu(NO3)2 is relatively important. When the Cu(NO3)2 content is between 0.01% and 0.1%, the voltage gradient decreases significantly. When the Cu(NO3)2 content is too high, the high concentration may cause copper ions to agglomerate, which in turn increases grain boundary defects and increases barrier fluctuations. Therefore, in the embodiment of the present invention, the Cu(NO3)2 content is between 0.03% and 0.05%.

[0027] In practical applications, Cu(NO3)2 has many effects on the performance of zinc oxide varistors, as follows:

[0028] 1. Improve energy tolerance:

[0029] ① Enhanced high-current shock resistance: The addition of Cu(NO3)2 can improve the performance of zinc oxide varistors under high-current shocks. It helps optimize the grain boundary characteristics between grains, making the grain boundary layer more resistant to chemical decomposition or structural damage caused by overheating when subjected to long-duration, high-energy shocks such as 10 / 350μs. This reduces problems such as increased leakage current and clamping voltage drift, reducing the risk of permanent failure.

[0030] ② Improve performance stability after multiple shocks: Under repeated surge shocks, zinc oxide varistors containing Cu(NO3)2 can better maintain nonlinear characteristics, and the protection threshold accuracy is relatively more stable, meeting the needs of long-term high reliability scenarios.

[0031] 2. Improve response speed and high-frequency characteristics:

[0032] ① Accelerate nanosecond fast pulse response: Cu(NO3)2 can promote the charge transfer inside the zinc oxide varistor, so that it can respond more quickly when facing high-frequency transient overvoltage with ns-level rising edges, reduce the clamping voltage overshoot phenomenon, and effectively protect high-frequency sensitive devices.

[0033] ② Reduce the impact of parasitic parameters: The addition of Cu(NO3)2 may help optimize the structure of the varistor and reduce parasitic inductance. In high-frequency applications, lower parasitic inductance can reduce voltage spikes and improve protection.

[0034] 3. Enhanced temperature stability:

[0035] ① Reduce performance fluctuations in high temperature environments: Cu(NO3)2 helps to adjust the temperature characteristics of the zinc oxide varistor, reduce the negative temperature coefficient of the varistor voltage (V1mA), make the clamping voltage more stable in high temperature environments (such as high power scenarios or ambient temperature > 85°C), and reduce the risk of false operation or protection failure.

[0036] ② Reduce the risk of thermal breakdown: Under high-energy impact, Cu(NO3)2 can make the temperature distribution inside the component more uniform and reduce local overheating, especially in miniaturized devices, which can effectively reduce the risk of thermal breakdown.

[0037] 4. Optimize capacitive characteristics:

[0038] ① Reduce leakage current in AC circuits: The presence of Cu(NO3)2 can reduce the parasitic capacitance of zinc oxide varistor, thereby reducing continuous leakage current in AC power lines, reducing component heating, and reducing fire hazards.

[0039] ② Reduce interference in high-frequency signal paths: In radio frequency or communication circuits, smaller parasitic capacitance can reduce coupling to signal energy, reduce signal attenuation or distortion, and improve the applicability of varistors in high-frequency systems.

[0040] It should be noted that the above mixture, zirconium balls, deionized water, adhesive, dispersant, and defoamer are mixed in a mass ratio of 1:1.5:1:0.12:0.1:0.1.

[0041] In practice, each raw material is weighed using precise weighing equipment to ensure that the sum of the components is 100%. The raw materials are then placed in a sand mill, along with zirconium balls, deionized water, a binder, a dispersant, and a defoamer. The zirconium balls act as a grinding medium, refining the raw material particles through collision and grinding under the high-speed operation of the sand mill. The deionized water acts as a medium and dispersant, preventing the introduction of impurities that could affect product performance. The binder ensures that the raw material particles maintain good formability during subsequent processing. The dispersant helps evenly disperse the raw materials and prevents agglomeration. The defoamer eliminates bubbles generated during mixing, ensuring uniformity of the material.

[0042] In step 102, the abrasive is spray granulated. The granulated particles need to pass through an 80-mesh sieve and a 200-mesh sieve. The two sieves can remove coarse materials larger than 80 mesh and fine materials smaller than 200 mesh. The particle size is finally controlled to be between 200 mesh and 80 mesh, and the moisture content of the particles is 0.6-0.8.

[0043] The sand-milled material undergoes spray granulation, a process in which the liquid material is dispersed into fine droplets through an atomizer. The hot air stream rapidly evaporates the water, forming solid particles. The advantage of spray granulation is that it can quickly dry the material, and the resulting particles have good flowability and dispersibility. The granulated particles need to be screened through 80-mesh and 200-mesh sieves. Coarse particles larger than 80 mesh are removed because they may lead to uneven density and surface roughness in the subsequent molding process, affecting product performance. Fine particles smaller than 200 mesh are prone to agglomeration and may cause defects such as pores due to uneven filling during the pressing process. The final particle size is controlled between 200 mesh and 80 mesh, with a moisture content between 0.6 and 0.8. These particles have good formability and flowability, ensuring smooth subsequent molding processes and positively affecting the final performance of the varistor.

[0044] Further, the screened granules were molded to a density of 3.25 g / m 3 ~3.35g / m 3 The screened granules are then formed into green sheets, typically using compression molding. During the molding process, the granules are placed in a mold and pressure is applied to compact the granules, forming green sheets of a defined shape and size. The appropriate density ensures a uniform internal structure during the subsequent pre-sintering and sintering processes, preventing defects such as cracking and deformation.

[0045] In step 103, the formed blank is pre-fired at 630°C for 8 hours to remove binder. It should be noted that the formed blank contains organic components such as binders and needs to be pre-fired to remove binder before high-temperature sintering. The blank is placed in a high-temperature furnace and pre-fired at 630°C for 8 hours to remove binder. During this process, organic substances such as binders will gradually decompose and volatilize. If binder removal is not performed, the rapid decomposition and volatilization of organic substances during the subsequent high-temperature sintering process may cause a large number of pores and cracks inside the blank, seriously affecting product quality. Pre-fired debinding not only removes organic components, but also makes the structure of the blank initially densified, improves the strength and stability of the blank, and prepares for the subsequent sintering process.

[0046] After debinding, the wafer is placed in a tunnel furnace for sintering, a critical process that determines the performance of the varistor. Firing is performed at 1100-1200°C for 25-30 hours, with a 4-hour hold period. During the heating process, the grains within the wafer gradually grow and develop, and the grain boundary structure continuously changes. The hold period ensures full grain growth and more stable grain boundaries, thereby optimizing the varistor's electrical properties, such as varistor voltage and nonlinear coefficient. The cooling process also requires strict control. Excessively rapid cooling can cause thermal stress within the wafer, leading to defects such as cracking.

[0047] It should be noted that, in the embodiment of the present invention, if the sintering temperature exceeds 900°C, Cu(NO3)2 and ZnO form a solid solution more fully, and the barrier reduction effect is more obvious; low-temperature sintering may lead to uneven copper distribution and affect consistency; preferably, when sintering in a tunnel furnace in the embodiment of the present invention, the sintering temperature is 1185°C and the temperature is kept for 3 hours.

[0048] The finished varistor is then cleaned, silver-sintered, inserted, soldered, encapsulated, cured, and then printed with markings. This series of precise manufacturing processes ultimately results in a varistor with excellent performance and reliable quality, widely used in various electronic devices and circuit systems, playing an important role in overvoltage protection.

[0049] In summary, the embodiment of the present invention provides a method for preparing a high-performance varistor, comprising: ZnO: Bi2O3: Sb2O3: Co3O4: MnCO3: Ni2O3: Cu(NO3)2: H3BO3: AgNO3: Al(NO3)2·9H2O in the following proportions: 89.13%-91.11%: 3.39%-4.15%: 2.95%-3.61%: 1.19%-1.45%: 0.70%-0.86%: 0.17%-0.21%: 0.03%-0 .05%: 0.38%-0.46%: 0.02%-0.04%: 0.02%-0.04% to obtain a mixture, the mixture is put into a sand mill with zirconium balls, deionized water, adhesive, dispersant, and defoaming agent for 4 hours to obtain abrasive; the abrasive is spray granulated, the obtained particles are passed through an 80-mesh sieve and a 200-mesh sieve to obtain granules, and the granules are pressed into blanks of a set density; the blanks are sequentially subjected to binder removal pre-sintering, tunnel furnace sintering, cleaning, silver burning, inserting, welding and encapsulation to obtain a varistor. Compared with the traditional zinc oxide varistor formula, in the embodiment of the present invention, Cu(NO3)2 is doped into the zinc oxide varistor formula. After adding Cu(NO3)2, the radius of the copper ion (Cu2+) (0.073nm) is the same as that of Zn 2+(0.074nm), easily entering the ZnO lattice or enriching at the grain boundary, forming a low-barrier interface; reducing the grain boundary barrier height, making it easier for electrons to cross the grain boundary, which is manifested macroscopically as a decrease in the varistor voltage, thereby causing a decrease in the voltage gradient (varistor voltage / thickness); at the same time, Cu(NO3)2 may inhibit ZnO grain growth, reduce grain size, increase the number of grain boundaries (reduced total grain boundary resistance), and further reduce the overall voltage gradient; this method not only improves the 8 / 20μs current-carrying capacity of the zinc oxide varistor, but also improves the 10 / 350μs current-carrying capacity. This solves the problem of existing zinc oxide varistors that have insufficient response speed, overshoot of the clamping voltage, and inability to effectively protect back-end equipment in a timely manner.

[0050] In order to more clearly introduce a method for preparing a high-performance varistor provided by an embodiment of the present invention, two methods for preparing high-performance varistors are introduced below.

[0051] Formula Ratio: There are two types: Formula 1 and Formula 2. Formula 1 does not contain copper nitrate, while Formula 2 does. In terms of weight, Formula 2 is made exactly like Formula 1, with copper nitrate added. The addition amounts are shown in Table 1 below (the table below lists the percentages by weight):

[0052] Table 1 Proportions according to mass percentage

[0053]

[0054] Specifically, according to the formula provided in Table 1, the prepared materials were added with zirconium balls, deionized water, a binder, a dispersant, and a defoamer. The mass ratio of the mixture: zirconium balls: deionized water: binder: dispersant: defoamer was 1:1.5:1:0.12:0.1:0.1, and then sand-milled for 4 hours.

[0055] The sand-milled slurry is spray-granulated. The resulting granules are screened through 80- and 200-mesh sieves, removing coarse particles larger than 80 mesh and fine particles smaller than 200 mesh. The final granules have a particle size between 200-80 mesh and a moisture content between 0.6-0.8. The screened granules are then formed into square green sheets with a thickness of 5.18mm and a diameter of 40.2mm x 40.2mm. The formed green sheets are then pre-sintered in a debinding furnace at 630°C for 8 hours. The debinded sheets are then sintered in a tunnel furnace at 1185°C for 25 hours, with a holding time of 3 hours.

[0056] After sintering, the sheet shrinks to a thickness of 4.35 mm. Finally, it is cleaned, silver-burned, inserted, welded, encapsulated, cured, and printed with a logo to obtain the finished product.

[0057] According to the national standard GB / T18802.11-2020 "Low Voltage Surge Protective Device SPD Part 11" 3.1.21 test 8 / 20μs current carrying capacity test, according to 8.4.4.6 Class III action load test test and 10 / 350μs current carrying capacity test, the test process is every 1min 20kA 8 / 20μs waveform shock once, for 5 consecutive times, after which it is placed in the air at room temperature for 30 minutes to cool down, and then every 1min 20kA 8 / 20μs waveform shock once, for 5 consecutive times, after three cycles, it is placed for one hour, and the 8 / 20μs current carrying capacity at 40kA is tested, and the 10 / 350μs current carrying capacity test at 7kA is tested. Six pieces of each formula and each group of experiments were randomly selected for comparison. The experimental data are shown in Tables 2 to 4:

[0058] Table 2. Comparison of static parameters

[0059]

[0060] 8 / 20μs current carrying capacity: shock once with 8 / 20μs waveform at intervals of 1 minute for 5 times in a row, then place in air at room temperature for 30 minutes to cool down, then shock once again with 8 / 20μs waveform at intervals of 20kA at intervals of 1 minute for 5 times in a row, after three cycles, place in air for one hour and test 40kA 8 / 20μs current carrying capacity. Specific data are shown in Table 3:

[0061] Table 3. 8 / 20μs flow capacity comparison

[0062]

[0063] 10 / 350μs current carrying capacity test: shock with 8 / 20μs waveform at 20kA every 1min for 5 times in a row, then place in air at room temperature for 30 minutes to cool down, then shock with 8 / 20μs waveform at 20kA every 1min for 5 times in a row, after three cycles, place in air for one hour and test the 10 / 350μs current carrying capacity at 7kA.

[0064] Table 4. 10 / 350μs flow capacity comparison

[0065]

[0066] Comparing the three sets of data presented in Tables 2 to 4 above shows that Formula 2, with the addition of copper nitrate, exhibits reduced leakage current, an increased nonlinear coefficient, and a reduced gradient. Varistors made with both formulas underwent three stages of 20kA shocks, five times, with voltage changes within 10%. Six samples of Formula 1 were subjected to a single 40kA shock; half passed with a change within 10%, while half failed. Formula 2, with the addition of copper nitrate, was tested using the same method and all passed.

[0067] After that, formula 1 and formula 2 with copper nitrate added were subjected to three stages of 20kA*5 8 / 20μs waveform shock, followed by a 7k 10 / 350μs shock. It was found that the change rate of formula 1 exceeded 10%, and three resistors exploded. Formula 2 was qualified, and the voltage change rate was within 10%. Analysis task: The grain boundaries between ZnO grains form Schottky barriers, which hinder electron migration. Sufficient voltage must be applied to enable electron transition to form current. After adding copper nitrate, copper ions (Cu 2+ ) radius (0.073nm) and Zn 2+ (0.074nm), it is easy to enter the ZnO lattice or be enriched at the grain boundary to form a low barrier interface. Secondly, copper ions reduce the height of the grain boundary barrier, making it easier for electrons to cross the grain boundary. Macroscopically, it is manifested as a decrease in the varistor voltage, which leads to a decrease in the voltage gradient (varistor voltage / thickness). At the same time, copper nitrate may inhibit the growth of ZnO grains, reduce the grain size, increase the number of grain boundaries (reduce the total resistance of grain boundaries), and further reduce the overall voltage gradient.

[0068] The addition of copper nitrate to a varistor modifies the microstructure of the varistor's ceramic body. For example, it promotes grain growth, resulting in more uniform grain size and denser grain boundaries. This optimized microstructure facilitates electron transport and migration during overvoltage surges with 8 / 20μs and 10 / 350μs waveforms, enabling a faster and more effective response to overvoltage events, limiting voltage rise and reducing residual voltage. Copper nitrate affects the chemical composition and electrical properties of the varistor's grain boundaries. It reduces the barrier height at the grain boundaries, enabling conduction at lower voltages. This lowers the varistor's initial operating voltage when subjected to 8 / 20μs and 10 / 350μs waveforms, enabling a more sensitive response to overvoltage events. Furthermore, the optimized grain boundary characteristics help stabilize voltage limiting during high-current surges, improving current capacity. Copper nitrate has excellent thermal conductivity, and its addition to the varistor improves its overall heat dissipation capabilities. The high-energy, short-duration impacts of the 8 / 20μs waveform and the long-duration impacts of the 10 / 350μs waveform generate heat in the varistor. Copper nitrate helps dissipate this heat quickly, preventing the varistor from overheating and potentially causing performance degradation or damage. This improves its energy handling capability and stability under both waveforms.

[0069] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A method for preparing a high-performance varistor, characterized in that: include; ZnO:Bi2O3:Sb2O3:Co3O4:MnCO3:Ni2O3:Cu(nO3)2:H3bO3:AgNO3:Al(NO3)2·9H2O are mixed in the following ratios: 89.13%-91.11%:3.39%-4.15%:2.95%-3.61%:1.19%-1.45%:0.70%-0.86%:0.17%-0.21%:0.03%-0.05%:0.38%-0.46%:0.02%-0.04%:0.02%-0.04% to obtain a mixture, and the mixture, zirconium balls, deionized water, a binder, a dispersant, and a defoaming agent are put into a sand mill and sanded for 4 hours to obtain an abrasive; Spray granulating the abrasive material, passing the obtained particles through an 80-mesh sieve and a 200-mesh sieve to obtain granules, and pressing the granules into blanks of a set density; The blank is sequentially subjected to binder removal and pre-sintering, tunnel furnace sintering, cleaning, silver burning, sheet insertion, welding and encapsulation to obtain a varistor.

2. The method according to claim 1, wherein The set density is 3.25g / m 3 -3.35g / m 3 .

3. The method according to claim 1, wherein The blank is subjected to binder removal and pre-sintering in sequence, specifically comprising: The blank is pre-sintered at 630°C for 8 hours to remove binder; The tunnel furnace sintering specifically includes: The debinding and pre-sintered blank is placed in a tunnel furnace for sintering at 1100-1200° C. for 25-30 hours and kept warm for 4 hours.

4. The method according to claim 1, wherein The sintering temperature is 1185° C. and the holding time is 3 hours.

5. The method according to claim 1, wherein The method comprises mixing the mixture, zirconium balls, deionized water, adhesive, dispersant and defoamer in a mass ratio of 1:1.5:1:0.12:0.1:0.1 before putting the mixture into a sand mill and sanding for 4 hours.

6. The method according to claim 1, wherein The particle size of the granulated material is between 200 meshes and 80 meshes, and the moisture content is 0.6-0.8.

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