Wide-temperature-range low-temperature sintering medium-voltage zinc oxide voltage-sensitive ceramic material and preparation method thereof

Abstract

The invention belongs to the field of electrical materials and preparation, and particularly discloses a wide-temperature-range low-temperature sintered medium-voltage zinc oxide voltage-sensitive ceramic material and a preparation method thereof. The voltage-sensitive ceramic material is composed of ZnO, Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, Al2O3 and CaO according to the molar ratio of the ZnO to the Bi2O3 to the Sb2O3 to the CoO to the MnO2 to the NiO to the Cr2O3 to the Al2O3 to the CaO of (97.000 to 98.500) to (0.050 to 0.500) to (0.0125 to 0.0500) to (0.200 to 1.600) to (0.010 to 0.300) to (0.100 to 0.800) to (0.010 to 0.050) to (0.025 to 0.100) to (0.010 to 0.200), the total molar amount of all the components is 100 percent, and the molar ratio of Bi to Sb is (4 to 8) to 1. The preparation method comprises the following steps: preparing a main material ZnO and an additive metal element salt, and carrying out high-energy ball milling to obtain slurry; and calcining the slurry, controlling the average particle size of the obtained composite powder to be less than 0.3 mu m, granulating the composite powder, removing plastic, and sintering to finally obtain the product with the voltage gradient E1mA of 200-230 V / mm. The zinc oxide voltage-sensitive ceramic material is good in performance, the energy consumption in the preparation process is reduced, the influence of sintering temperature fluctuation on the performance of the zinc oxide voltage-sensitive ceramic material is reduced, the consistency of the product performance is ensured, and a thought is expected to be provided for industrial low-carbon production.

Description

Technical Field

[0001] This invention belongs to the field of electrical materials and preparation, specifically relating to a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material and its preparation method. Background Technology

[0002] Zinc oxide (ZnO) varistors are widely used in the power and electronics fields due to their excellent nonlinear voltage-current characteristics and transient surge current absorption capabilities. It is a ceramic material that utilizes the Schottky grain boundary barrier to generate a nonlinear resistance effect. ZnO ceramic varistors are used as core components of surge arresters, and currently, commercially available varistors have a voltage gradient of 200~300V / mm.

[0003] The microstructure of ZnO varistors consists of ZnO grains doped with donor impurities (the main phase) and a bismuth-rich grain boundary layer (the second phase) containing a large amount of metal oxide interface states. The performance of ZnO varistors is directly related to their microstructure. It is generally believed that their voltage gradient is directly proportional to the number of grain boundaries per unit thickness in the ceramic and inversely proportional to the average ZnO grain size. The voltage drop at a single grain boundary is approximately 3V and does not change with the formulation or process. Therefore, to obtain a voltage gradient of 200–300V / mm, a ZnO grain size of approximately 10–15μm is required, and the sintering temperature for most industrial production is typically between 1100–1300℃. However, Bi₂O₃ has a melting point of 825℃, and Sb₂O₃ has a melting point of 655℃. During high-temperature sintering, these particles are prone to volatilization, leading to increased porosity, reduced microstructure uniformity, and deterioration of electrical properties in the ZnO varistors. Therefore, reducing the sintering temperature of ZnO varistors is crucial. However, lowering the sintering temperature often inhibits ZnO grain growth, which in turn increases the voltage gradient, creating a contradiction.

[0004] In ZnO-Bi2O3 varistor formulations, Bi2O3 and Sb2O3 are two important additives. Bi2O3, by forming a Bi-rich phase at ZnO / ZnO grain boundaries, is the true factor promoting liquid-phase sintering and is key to the grain boundary effect. Sb2O3, generally considered to form spinel and pyrochlore phases, inhibits grain growth. The uniform distribution of both around ZnO grains is crucial for improving the uniformity of the ceramic microstructure. During sintering, when the temperature reaches approximately 740℃, the molten free Bi2O3 combines with ZnO to form a eutectic compound, indicating the beginning of a liquid phase in the sintering system. As the temperature continues to rise, sintering progresses rapidly. Therefore, literature review and experimental research revealed that even a 10°C difference in sintering temperature under the same formula and process conditions can lead to different average ZnO grain sizes, resulting in significant differences in voltage gradients. In actual production, furnace temperature fluctuates within a certain range, and temperatures also vary at different locations within the furnace, easily causing poor performance consistency within the same batch of products and reducing product yield. Therefore, there is an urgent need to develop a method for preparing medium-pressure zinc oxide varistor ceramic materials using low-temperature sintering over a wider temperature range to improve product performance consistency while reducing energy consumption. Summary of the Invention

[0005] One objective of this invention is to provide a wide-temperature-range, low-temperature sintered, medium-pressure zinc oxide varistor ceramic material with a voltage gradient. E 1mA 200~230V / mm, nonlinear coefficient α The value is 25~35, leakage current I L With an A value of ≤5μA, the impact of sintering temperature fluctuations during the preparation process on the performance of zinc oxide varistor ceramics is reduced, ensuring the consistency of product performance and potentially providing a solution for low-carbon industrial production.

[0006] The second objective of this invention is to provide a method for preparing medium-pressure zinc oxide varistor ceramic materials by low-temperature sintering over a wide temperature range, which corresponds to one of the technical problems. This method can be used to produce medium-pressure zinc oxide varistor ceramic materials, overcoming the problems of high sintering temperature, excessively high voltage gradient in materials caused by low-temperature sintering, and large influence of voltage gradient fluctuations on sintering temperature in the prior art.

[0007] The third objective of this invention is to provide a method for preparing a mass-producible, wide-temperature-range, low-temperature sintering medium-pressure zinc oxide varistor ceramic material, which corresponds to solving one of the technical problems. This method not only improves the performance of the zinc oxide varistor ceramic material but also promotes green manufacturing and reduces environmental pollution.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: The composition and molar ratio of the wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material are as follows: ZnO:Bi2O3:Sb2O3:CoO:MnO2:NiO:Cr2O3:Al2O3:CaO = (97.000~98.500):(0.050~0.500):(0.0125~0.0500):(0.200~1.600):(0.010~0.300):(0.100~0.800):(0.010~0.050):(0.025~0.100):(0.010~0.200), with the total molar amount of each component being 100%, and the molar ratio of Bi:Sb = (4~8):1.

[0009] Among these additive elements, Bi and Sb are the two most important additives in Bi-based varistors. During sintering, Bi promotes liquid-phase sintering by forming a Bi-rich phase at ZnO / ZnO grain boundaries, and simultaneously promotes the distribution of other additive elements such as Co, Mn, and Ni at the grain boundaries, playing a key role in the formation of the grain boundary effect. Sb, on the other hand, mainly forms spinel and pyrochlore phases with Zn, anchoring them at the grain boundaries and inhibiting grain growth. The content and ratio of these two elements directly affect the subsequent sintering behavior, as well as the subsequent microstructure and grain boundary characteristics. For medium-pressure zinc oxide varistors, the Sb content needs to be appropriately reduced, hence the molar ratio of Bi to Sb was set. Co, Mn, Ni, Cr, and Al are mainly used to improve nonlinearity. Simultaneously, high-energy ball milling is used to refine the raw materials, improving the powder sintering activity and lowering the sintering temperature.

[0010] Specifically, the present invention also discloses a method for preparing the wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material, comprising the following steps: (a) Preparation of ultrafine composite powder: Weigh the main material zinc oxide and additives according to the proportion, wherein the molar proportion of the main material zinc oxide is 97.000%~98.500%, and the remainder is additives; the additives are selected from the salts corresponding to the metal elements, and their elemental composition and molar ratio are: Bi : Sb : Co : Mn : Ni : Cr : Al : Ca : = (0.100~1.000) : (0.025~0.100) : (0.200~1.600) : (0.010~0.300) : (0.100~0.800) : (0.020~0.100) : (0.050~0.200) : (0.010~0.200), and the molar ratio Bi : Sb = (4~8) : 1.

[0011] After the raw materials are mixed, they are subjected to high-energy ball milling with water as the medium, wherein the material-to-ball ratio is (1:10) to (1:2), the rotation speed is 400 to 1000 r / min, and the ball milling time is 2 to 10 h; the slurry is dried at 100 to 130 ℃ for 2 to 10 h; the dried material is then calcined at 300 to 550 ℃ for 3 to 10 h; after calcination, the powder is ground and sieved to ensure that the average particle size is less than 0.3 μm.

[0012] (b) Add the binder to the above ultrafine composite powder, granulate and mold it, apply a pressure of 100~300MPa to obtain a green body, and then remove the plastic from the green body; (c) The green body after plastic removal is sintered. Under normal pressure, the temperature is first raised to 740~820℃ at a heating rate of 0.50~3.0℃ / min, and then raised to the sintering temperature of 850~980℃ at a heating rate of 1.0~15.0℃ / min. The temperature is held for 2.0~5.0h to obtain a zinc oxide varistor ceramic material with good comprehensive performance.

[0013] Preferably, the salt corresponding to the metal element in the additive is one of nitrate, acetate, or citrate.

[0014] Preferably, the ball-to-material ratio of the high-energy ball mill in step (a) is (1:6) to (1:3), the rotation speed is 450 to 800 r / min, and the milling time is 4 to 6 h.

[0015] Preferably, the slurry in step (a) is dried in a forced-air drying oven at a temperature of 105~125℃ for 3~6 hours.

[0016] Preferably, the calcination temperature in step (a) is 360~480℃ and the time is 6~8 h.

[0017] Preferably, the average particle size of the ultrafine composite powder obtained in step (a) is 0.1~0.3μm.

[0018] Preferably, the binder in step (b) is a PVA aqueous solution (concentration 5 wt.%), and the amount of the binder is 10-20 wt.% of the powder weight, more preferably 12-15 wt.%.

[0019] Preferably, the molding pressure in step (b) is 150~250MPa.

[0020] Preferably, the discharge temperature in step (b) is 450~550℃, more preferably 490~510℃.

[0021] Preferably, in step (c), the temperature is first raised to 750-800°C at a heating rate of 1.0-2.0°C / min, and then raised to a sintering temperature of 880-980°C at a heating rate of 3.0-10.0°C / min for sintering for 3.0-5.0 hours.

[0022] The preparation method includes the preparation of ultrafine composite powder, the selection of calcination and desizing temperature, and the design of the sintering process. The overall goal is to fully utilize and maintain the compositional uniformity and high sintering activity of the ultrafine composite powder, achieve full development of the microstructure at a lower sintering temperature, and reduce or even avoid changes in the degree of microstructure development caused by fluctuations in sintering temperature.

[0023] (1) Preparation of ultrafine composite powder. First, in terms of raw material selection, ZnO powder is used as the main material, with an average particle size of less than 0.3 μm, which is beneficial for manufacturing pressure-sensitive ceramic materials with excellent performance. The total proportion of additives in the formula is only 1.5~3.0 mol%, so using the salt corresponding to the metal element of the additive as the raw material will help improve the uniformity of the distribution of the additive around the ZnO powder particles at the molecular level. The salt corresponding to the metal element of the additive undergoes a series of ceramic processes, and finally decomposes into corresponding oxides during the plasticizing and sintering stages. Then, further physical and chemical processes occur to obtain zinc oxide pressure-sensitive ceramic materials. Finally, the prepared raw materials are refined by high-energy ball milling, which can improve the sintering activity of the powder and help reduce the sintering temperature.

[0024] (2) Temperature selection during calcination. While maintaining the high sintering activity of the ultrafine composite powder, calcination removes the polymer material of the ball mill jar that may be introduced during the ball milling process. Therefore, the temperature selection during calcination is very important. Too high a temperature may cause some of the ultrafine powder to soften, sinter, or even melt, entering the early stage of sintering in advance, thus losing some of its sintering activity. Too low a temperature may not be able to guarantee the decomposition and discharge of the polymer organic matter, or even produce carbon deposits.

[0025] (3) Sintering process design. A suitable Bi2O3 content and the ratio of Bi2O3 to Sb2O3 can provide a suitable bismuth-rich phase at temperatures above 740℃ (the eutectic point of ZnO and Bi2O3 is about 740℃). Therefore, during the sintering process, the temperature is first raised slowly, gradually passing through the temperature range where the liquid phase begins to form to the most abundant phase. This is beneficial to ensure that the Bi2O3-based liquid phase is evenly distributed around the ZnO grains at a lower temperature, while maintaining the sintering activity of the ultrafine powder. Then, the temperature is raised to a higher sintering temperature at a faster rate and held for several hours for sintering to complete the full development of the microstructure and establish an effective grain boundary barrier.

[0026] The above formula and preparation method together realize the preparation of the medium-pressure zinc oxide varistor ceramic material with wide temperature range low-temperature sintering of the present invention. Attached Figure Description

[0027] Figure 1 The image shows the morphology of the ultrafine composite powder in Example 1. Figure 2 This is a particle size distribution diagram of the ultrafine composite powder in Example 1; Figure 3 Microscopic images of the ceramic materials prepared in Examples 1-4; Figure 4 The current density-electric field intensity curves of the ceramic materials obtained in Examples 11, 15, Comparative Example 1, and Comparative Example 2 are shown. Detailed Implementation

[0028] The present invention is further illustrated below by way of examples, but the present invention is not limited thereto. Unless otherwise specified, the preparation methods and usage conditions used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available. Example 1

[0029] A method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material, wherein the molar proportion of the main material ZnO is 98.350%, and the molar ratio of the nitrates of other additive metal elements is: Bi : Sb : Co : Mn : Ni : Cr : Al : Ca : = 0.600 : 0.100 : 0.600 : 0.010 : 0.200 : 0.040 : 0.060 : 0.040, the total molar amount of all raw materials is 100%, and the molar ratio Bi : Sb = 6 : 1.

[0030] After mixing the raw materials, high-energy ball milling was performed using water as the medium, with a material-to-ball ratio of 1:3, a rotation speed of 500 r / min, and a milling time of 6 h. The slurry was dried in a forced-air drying oven at a set temperature of 120℃ for 4 h. The dried material was then calcined at 360℃ for 6 h. After calcination, the powder was milled and sieved to ensure that the average particle size of the obtained ultrafine composite powder was less than 0.3 μm. A binder accounting for 12 wt.% of the powder weight was added to the above ultrafine composite powder, followed by granulation, molding, and application of 200 MPa pressure to obtain a green body. The green body was then de-plasticized at 480℃. Under normal pressure, the green body was first heated to 750℃ at a heating rate of 1.0℃ / min, and then heated to the sintering temperature of 880℃ at a heating rate of 5.0℃ / min and held for 3.0 h for sintering, resulting in a zinc oxide varistor ceramic material with good comprehensive performance. Its microstructure is as follows: Figure 3 As shown in (a).

[0031] The voltage gradient of the obtained zinc oxide varistor ceramic material was measured. E 1mA 221V / mm, nonlinear coefficient α The value is 25, leakage current I L It is 2μA.

[0032] The morphology of the composite powder prepared in Example 1 is as follows: Figure 1 As shown, the powder particles are uniform in size and have a near-spherical shape. The particle size distribution of the composite powder is as follows: Figure 2 As shown, the average particle size is 0.26 μm. Example 2

[0033] Zinc oxide varistor ceramic material was prepared using the same formulation and method as in Example 1, except that the sintering temperature in the second step was 900°C.

[0034] The microstructure of the zinc oxide varistor ceramic material is as follows: Figure 3 As shown in (b). The voltage gradient of the obtained zinc oxide varistor material was measured. E 1mA 220V / mm, nonlinear coefficient α The value is 25, leakage current I L It is 1 μA. Example 3

[0035] Zinc oxide varistor ceramic material was prepared using the same formulation and method as in Example 1, except that the sintering temperature in the second step was 920°C.

[0036] The microstructure of the zinc oxide varistor ceramic material is as follows: Figure 3 As shown in (c). The voltage gradient of the obtained zinc oxide varistor material was measured. E 1mA 218V / mm, nonlinear coefficient α The value is 26, leakage current I L It is 1.5 μA. Example 4

[0037] Zinc oxide varistor ceramic material was prepared using the same formulation and method as in Example 1, except that the sintering temperature in the second step was 940°C.

[0038] The microstructure of the zinc oxide varistor ceramic material is as follows: Figure 3 As shown in (d), the potential gradient of the obtained zinc oxide varistor material was measured. E 1mA 215V / mm, nonlinear coefficient α The value is 28, leakage currentI L It is 2μA.

[0039] Figure 3 The images show the microstructure of the ceramic materials prepared in Examples 1-4 above. In the images, Z represents ZnO grains, B represents Bi-rich phase, and S represents spinel phase. As can be seen from the images, the ceramics have high density and uniform microstructure. From Example 1 to Example 4, the sintering temperature gradually increases, and the average grain size of ZnO grows slowly, with values ​​of 9.52 μm, 9.83 μm, 10.62 μm, and 11.50 μm, respectively. Example 5

[0040] A method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material, wherein the molar proportion of the main material ZnO is 97.820%, and the molar ratio of the acetates of other additive metal elements is: Bi : Sb : Co : Mn : Ni : Cr : Al : Ca : = 0.400 : 0.080 : 1.200 : 0.060 : 0.200 : 0.040 : 0.100 : 0.100, the total molar amount of all raw materials is 100%, and the molar ratio Bi : Sb = 5 : 1.

[0041] After mixing the raw materials, high-energy ball milling was performed using water as the medium, with a material-to-ball ratio of 1:6, a rotation speed of 500 r / min, and a milling time of 6 h. The slurry was dried in a forced-air oven at a set temperature of 120℃ for 4 h; the dried material was then calcined at 360℃ for 6 h; after calcination, the powder was milled and sieved to ensure that the average particle size of the obtained ultrafine composite powder was less than 0.3 μm. A binder accounting for 15 wt.% of the powder weight was added to the above ultrafine composite powder, followed by granulation, molding, and application of 200 MPa pressure to obtain a green body. The green body was then de-plasticized at 500℃. Under normal pressure, the green body was first heated to 750℃ at a heating rate of 1.0℃ / min, and then heated to the sintering temperature of 900℃ at a heating rate of 5.0℃ / min and held for 3.0 h for sintering, resulting in a zinc oxide varistor ceramic material with excellent comprehensive performance.

[0042] The voltage gradient of the obtained zinc oxide varistor ceramic material was measured. E 1mA 210V / mm, nonlinear coefficient α The value is 28, leakage current I L It is 2.5 μA. Example 6

[0043] Zinc oxide varistor ceramic material was prepared using the same formulation and method as in Example 5, except that the salt corresponding to the additive metal element was selected as citrate.

[0044] The voltage gradient of the obtained zinc oxide varistor ceramic material was measured. E 1mA 214V / mm, nonlinear coefficient α The value is 25, leakage current I L It is 3.5 μA. Example 7-27

[0045] Zinc oxide varistor ceramic materials were prepared using the same steps as in Example 1, except that the formulation ratios and parameters during the preparation process were adjusted, and the ratio of Bi and Sb and the content of each additive were changed, as shown in Tables 1 and 2 below: Table 1. Mole percentage of raw materials in the formulations of Examples 7-27

[0046] Table 2 Parameter adjustments during the preparation process of Examples 7-27

[0047] Comparative Examples 1-2 The pressure-sensitive ceramic material was prepared using the same method and steps as in Example 1, except that the sintering temperature in the second step was 1000℃. The molar percentages of the raw materials in the formulations of Comparative Example 1 and Comparative Example 2 are shown in Table 3 below: Table 3. Mole percentage of raw materials in Comparative Example 1 and Comparative Example 2

[0048] The potential gradients of the zinc oxide varistor ceramic materials prepared in Examples 7-27 and Comparative Examples 1-2 were tested. E 1mA Nonlinear coefficients α and leakage current I L The results are shown in Table 4 below: Table 4 Performance parameters of the varistor ceramic materials in Examples 7-27 and Comparative Examples 1-2

[0049] Figure 4 The current density-electric field intensity curves of the ceramic materials obtained in Examples 11, 15, Comparative Example 1, and Comparative Example 2 are shown. The corresponding potential gradient of the zinc oxide varistor material is also shown. E 1mA The values ​​are 203V / mm, 200V / mm, 188V / mm, and 165V / mm, respectively, indicating that the formulation, preparation method, and synergistic effect of various parameters of the present invention can achieve high-performance medium-pressure zinc oxide varistor ceramic material through low-temperature sintering over a wide temperature range.

[0050] The above description merely illustrates preferred embodiments of the present invention, and while the description is specific and detailed, it should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications, improvements, and substitutions without departing from the concept of the present invention, and these all fall within the scope of protection of the present invention.

Claims

1. A wide-temperature-range, low-temperature sintered, medium-pressure zinc oxide varistor ceramic material, characterized in that: The composition and molar ratio of the pressure-sensitive ceramic material are as follows: ZnO:Bi2O3:Sb2O3:CoO:MnO2:NiO:Cr2O3:Al2O3:CaO = (97.000~98.500):(0.050~0.500):(0.0125~0.0500):(0.200~1.600):(0.010~0.300):(0.100~0.800):(0.010~0.050):(0.025~0.100):(0.010~0.200), the total molar amount of each component is 100%, and the molar ratio of Bi:Sb = (4~8):

1.

2. The wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 1, characterized in that: The voltage gradient of the varistor ceramic material E 1mA 200~230V / mm, nonlinear coefficient α The value is 25~35, leakage current I L ≤5μA.

3. A method for preparing a wide-temperature-range, low-temperature sintering, medium-pressure zinc oxide varistor ceramic material, characterized in that, Includes the following steps: (a) Preparation of ultrafine composite powder: Weigh the main material zinc oxide and additives according to the proportion, wherein the molar proportion of the main material zinc oxide is 97.000%~98.500%, and the remainder is additives; the additives are selected from the salts corresponding to the metal elements, and their elemental composition and molar ratio are: Bi : Sb : Co : Mn : Ni : Cr : Al : Ca : = (0.100~1.000) : (0.025~0.100) : (0.200~1.600) : (0.010~0.300) : (0.100~0.800) : (0.020~0.100) : (0.050~0.200) : (0.010~0.200), and the molar ratio Bi : Sb = (4~8) : 1; After the raw materials are mixed, they are subjected to high-energy ball milling with water as the medium, wherein the material-to-ball ratio is (1:10) to (1:2), the rotation speed is 400 to 1000 r / min, and the ball milling time is 2 to 10 h; the slurry is dried at 100 to 130 ℃ for 2 to 10 h; the dried material is then calcined at 300 to 550 ℃ for 3 to 10 h; after calcination, the powder is ground and sieved to ensure that the average particle size is less than 0.3 μm; (b) Add the binder to the above ultrafine composite powder, granulate and mold it, apply a pressure of 100~300MPa to obtain a green body, and then remove the plastic from the green body; (c) The green body after plastic removal is sintered. Under normal pressure, the temperature is first raised to 740-820℃ at a heating rate of 0.50-3.0℃ / min, and then raised to the sintering temperature of 850-980℃ at a heating rate of 1.0-15.0℃ / min and held for 2.0-5.0h to obtain the zinc oxide pressure-sensitive ceramic material.

4. The preparation method of a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, The salt corresponding to the metal element in the additive is one of nitrate, acetate, or citrate.

5. The method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, The ball-to-material ratio of the high-energy ball mill in step (a) is (1:6) to (1:3), the rotation speed is 450 to 800 r / min, and the ball milling time is 4 to 6 h.

6. The method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, The slurry described in step (a) is dried in a forced-air drying oven at a temperature of 105~125℃ for 3~6 hours.

7. The method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, The calcination temperature in step (a) is 360~480℃ and the time is 6~8h.

8. The method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, In step (b), the molding pressure is 150~250MPa.

9. The method for preparing a wide-temperature-range low-temperature sintering medium-pressure zinc oxide varistor ceramic material according to claim 3, characterized in that, In step (c), the temperature is first raised to 750-800℃ at a heating rate of 1.0-2.0℃ / min, and then raised to the sintering temperature of 880-980℃ at a heating rate of 3.0-10.0℃ / min for sintering for 3.0-5.0h.

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