Novel alternating-current and direct-current high-stability ZnO piezoresistor and preparation method thereof

Abstract

The invention relates to a novel alternating-current and direct-current high-stability ZnO piezoresistor and a preparation method thereof. The ZnO varistor is composed of ZnO, a compound containing a Cr element and a modified doping agent, wherein the content of the ZnO is 74 to 99.995 mol%, the content of the Cr element is 0.005 to 4 mol%, the content of the modified dopant is 0 to 22 mol%, and the sum of the molar contents of the components is 100 mol%; the modified dopant is composed of a compound containing at least one of Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si and Ti elements.

Description

Technical Field

[0001] The invention belongs to the technical field of varistors, and in particular relates to a novel AC and DC high-stability ZnO varistor and a preparation method thereof. Background Art

[0002] Zinc oxide varistors have excellent nonlinear volt-ampere characteristics and simple process and low cost. Therefore, zinc oxide varistors are mainly used as overvoltage protectors for various electrical equipment and lightning arresters, and are widely used in communications, electronic components, automobile industry, and medical industry. The main function of varistors is to suppress surges to protect equipment lines. At present, with the continuous innovation and improvement of industrial technology, varistors are constantly subjected to working voltages and intermittently subjected to instantaneous lightning overvoltages and operating overvoltages of different amplitudes and pulse widths, which will cause their electrical performance to deteriorate and even fail, affecting the long-term, stable and reliable operation of the power system. Among them, AC aging and DC aging are aging phenomena caused by ZnO varistors being subjected to working voltages for a long time. Therefore, this puts higher requirements on the stability and service life of ZnO varistors in AC and DC working environments. For this reason, it is urgent to develop a new type of high-stability ZnO varistor that is resistant to AC and DC applications, which conforms to the development trend of varistors and has broad application prospects. Summary of the invention

[0003] In view of the above problems, the present invention designs and prepares a novel AC and DC high-stability zinc oxide varistor, which has a smaller initial leakage current and prolongs the working life in AC and DC environments.

[0004] On the one hand, the present invention provides a novel AC and DC high-stability ZnO varistor, the ZnO varistor is composed of ZnO, a compound containing Cr and a modified dopant; wherein the content of ZnO is 74-99.995 mol%, the content of Cr is 0.005-4 mol%, the content of the modified dopant is 0-22 mol%, and the sum of the molar contents of each component is 100 mol%; the modified dopant is composed of a compound containing at least one of Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si and Ti elements.

[0005] In the modified dopant, the contents of each element are: Ca: 0-4mol%, Co: 0-2mol%, Sb: 0-1.5mol%, Mn: 0-4mol%, Ni: 0-1mol%, Ba: 0-1mol%, Al: 0-1.5mol%, Mg: 0-2mol%, B: 0-1mol%, In: 0-0.5mol%, La: 0-2mol%, Y: 0-1mol%, Ga: 0-0.5mol%, Si: 0-1mol%, Ti: 0-1mol%.

[0006] Preferably, the nonlinear coefficient α of the ZnO varistor is ≥ 8, and the leakage current I L ≤100μA; At 80% V 1mA After aging for 160 hours at 135°C under AC voltage, the varistor voltage change rate does not exceed 10%, and the leakage current I L ≤200μA, aging coefficient K T ≤100μA / h 1 / 2 ; At 80% V 1mA After aging for 160 hours at 135°C under a DC voltage, the varistor voltage change rate does not exceed 10%, and the leakage current I L ≤200μA, aging coefficient K T ≤100μA / h 1 / 2 .

[0007] Based on the traditional zinc oxide varistor, the present invention uses ZnO as the main body, adopts a compound containing Cr as a varistor performance activator, and uses a compound containing at least one of Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si, and Ti as a modified dopant to prepare a ZnO varistor with high stability in AC and DC environments. The initial leakage current I L Lower, I L ≤100μA, good anti-aging performance in AC and DC environments.

[0008] On the other hand, the present invention provides a method for preparing the above-mentioned novel AC and DC high-stability ZnO varistor, comprising: mixing zinc oxide, a compound containing Cr element and a modified dopant, and obtaining a composite powder through ball milling, drying and synthesis; adding a binder to the composite powder for granulation to obtain granulated powder; and pressing, debinding and sintering the granulated powder to obtain the ZnO varistor.

[0009] Preferably, the parameters of the ball milling include: using deionized water as the ball milling medium, the ball milling speed is 400-1000 rpm, the ball milling time is 2-12 hours, and the material-ball ratio is 1:1-20:1.

[0010] Preferably, the drying temperature is 100-120°C.

[0011] Preferably, the synthesis temperature is 300-700° C. and the time is 1-4 hours.

[0012] Preferably, the pressure of the pressing molding is 100-250 MPa; The debinding temperature is 350-800° C. and the time is 1-10 hours.

[0013] Preferably, the sintering parameters include: a sintering temperature of 800 to 2500° C., a sintering time of 1 to 8 hours, and a heating rate of 0.5 to 10° C. / min.

[0014] Preferably, the preparation method further comprises: polishing the sintered sample and brushing a silver electrode on the surface thereof to obtain the ZnO varistor.

[0015] The present invention adopts ZnO as the main component to prepare a novel AC and DC high-stability varistor, and by adding at least one of Cr, Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si, and Ti elements, the proportion of doping elements is continuously adjusted until the compactness at the grain boundary of the varistor is effectively improved, the grain boundary barrier height is increased, thereby reducing the initial leakage current of the varistor, and obtaining a varistor with high stability and resistance to AC and DC aging performance.

[0016] Compared with the traditional zinc oxide varistor, the zinc oxide varistor prepared by the present invention does not contain Bi2O3 which is volatile at high temperature, does not contain expensive preparation elements (such as Pr), and does not contain toxic elements (such as V). The nonlinear coefficient (IV nonlinear coefficient) of the obtained novel zinc oxide varistor is α≥8, and the leakage current I L ≤100μA, respectively at 80%·V 1mA The varistor voltage change rate does not exceed 10% after aging for 160 hours at 135℃. The aging coefficient K T ≤100μA / h 1 / 2 , the anti-aging performance is significantly improved.

[0017] Beneficial effects: (1) The novel AC and DC high-stability ZnO varistor prepared by the present invention has a small leakage current of less than 100 μA and has stable AC and DC aging resistance, with an aging temperature of 135°C and 80%·V 1mA After 160h of continuous accelerated aging under AC and DC, it still maintains good varistor properties. (2) The preparation method of the ZnO varistor provided by the present invention has the advantages of less doping elements, low cost, simple preparation process, green and environmental protection, etc., and has practicality and application prospects. DETAILED DESCRIPTION

[0018] In order to further illustrate the content, features and practical effects of the present invention, the present invention is described in detail in conjunction with the embodiments below. It should be pointed out that the modification method of the design of the present invention is not limited to these specific implementation methods. Without departing from the spirit and connotation of the design of the present invention, the equivalent substitutions and modifications made by those skilled in the art based on the content of the present invention are also within the scope of protection required by the present invention. In the present invention, the molar percentage (mol%) refers to the percentage value of the molar number of the composition to the sum of the molar numbers of all compositions. The leakage current refers to the current flowing through the varistor when the circuit to which the varistor is applied is operating normally.

[0019] The present invention takes ZnO as the main body, and prepares a novel ZnO varistor with high AC and DC stability by adding a compound containing the Cr element as a varistor performance stimulator and a compound containing at least one of the Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si, and Ti elements as a modified dopant. Wherein, the content of ZnO is 74-99.995 mol%, the content of Cr element is 0.005-4 mol%, the content of modified dopant is 0-22 mol%; the sum of the molar contents of each component is 100 mol%; in the modified dopant, the contents of each element are respectively: Ca: 0-4 mol%, Co: 0-2 mol%, Sb: 0-1.5 mol%, Mn: 0-4 mol%, Ni: 0-1 mol%, Ba: 0-1 mol%, Al: 0-1.5 mol%, MgO: 0-2 mol%, B: 0-1 mol%, In: 0-0.5 mol%, La: 0-2 mol%, Y: 0-1 mol%, Ga: 0-0.5 mol%, Si: 0-1 mol%, Ti: 0-1 mol%. In addition, it should be understood that other dopants may be contained in the novel AC and DC high stability ZnO varistor within the scope of not affecting the purpose of the present invention.

[0020] In the present invention, ZnO is used as the main component of the zinc oxide varistor, and its content is 74-99.995 mol%, preferably 80-99.5 mol%. If the content of ZnO is lower than 74 mol%, the nonlinear coefficient will be reduced, which is not conducive to industrial production; if the content of ZnO is higher than 99.995 mol%, the nonlinear coefficient is small. The content of Cr element is 0.005-4 mol%, preferably 0.02-3 mol%, and its main function is to generate or increase the nonlinear coefficient. If the content of Cr element is lower than 0.005%, there is basically no nonlinear coefficient; if the content of Cr element is higher than 4 mol%, the nonlinear coefficient is reduced. The compound containing Cr element may be Cr2O3. Cr2O3 is used to generate or increase the nonlinear coefficient, and its content is 0.0025-2 mol%, preferably 0.0025-1.5 mol%. A compound containing at least one of the elements Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si, and Ti is used as a modified dopant, with a content of 0.005 to 22 mol%. The main functions are: improving the nonlinear coefficient, reducing the initial leakage current, and improving the anti-aging performance of the varistor under AC and DC environments. In the present invention, by appropriately adjusting the proportion of the main Zn and Cr elements, the unstable ion migration in the grain boundary is suppressed, thereby improving its anti-AC and DC load aging ability, and by adding a certain proportion of compounds containing at least one of the elements Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si, and Ti, the Schottky barrier height at the grain boundary is effectively increased, and the phenomenon of large initial leakage current is improved, thereby making the DC performance of the varistor of this system more stable. The leakage current I of the zinc oxide varistor prepared by the present invention is L ≤100μA, even as low as below 50μA, indicating that the sample has low energy loss and good stability.

[0021] The following is an exemplary description of the preparation method of the novel AC and DC high-stability ZnO varistor provided by the present invention.

[0022] The zinc oxide, the compound containing the Cr element and the modified dopant are mixed, ball-milled, dried and synthesized to obtain a composite powder.

[0023] In an optional embodiment, the ball milling parameters include: using zirconium oxide balls or stainless steel balls, wet grinding with water as the medium in a planetary ball mill, the ball milling speed is 400-1000 rpm, the ball milling time is 4-10 hours, and the material-ball ratio is 1:1-20:1.

[0024] In an optional embodiment, the drying temperature is 100-120°C.

[0025] In an optional embodiment, the synthesis temperature is 300-700° C. and the time is 1-4 hours.

[0026] A binder (eg, 10 wt % PVA) is added to the composite powder and granulated to obtain granulated powder.

[0027] The granulated powder is subjected to compression molding, debinding and sintering to obtain the ZnO varistor.

[0028] In an optional embodiment, the compression molding pressure is 100-250 MPa.

[0029] In an optional embodiment, the debinding temperature is 350-800° C. and the time is 1-10 hours.

[0030] In an optional embodiment, the sintering parameters include: a sintering temperature of 800 to 2500°C, a sintering time of 1 to 8 hours, and a heating rate of 0.5 to 10°C / min; preferably, the sintering temperature is 1100 to 1300°C, and the time is 1 to 8 hours. As a preferred example, the ceramic green body is heated from room temperature to 1100 to 1200°C at 4 to 5°C / min, kept warm for 3 hours, and then cooled with the furnace to obtain a high-density zinc oxide varistor.

[0031] Test method: (1) Varistor voltage: The voltage across the varistor when a specified current density is passed. Generally, the current density flowing through the sample is 1 mA / cm 2 When the voltage across the sample is V 1mA To express the varistor voltage (breakdown voltage); IV nonlinear coefficient α: calculated as follows: Where V1 and V2 are voltage values ​​corresponding to currents I1 = 0.1 mA and I2 = 1 mA; Leakage current I L : The current flowing through the varistor under normal working voltage before it enters the breakdown region is called leakage current. In practical applications, the working voltage is generally taken as 75%·V 1mA The current when . (2) Aging method: Select 80% V 1mA The voltage value is used as the aging voltage, the temperature is 135℃, and the aging time is 160 hours. Aging coefficient K T Satisfies the following formula: Among them I L is the leakage current after aging, I is the initial leakage current, and h is the aging time.

[0032] The following further examples are given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention. The specific process parameters and the like in the following examples are also only examples within a suitable range, that is, those skilled in the art can make a selection within a suitable range through the description herein, and are not limited to the specific values ​​​​exemplified below.

[0033] Example 1

[0034] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 1 includes: ZnO (93.4 mol%), CaCO3 (3 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.1 mol%), MnO2 (0.5 mol%), NiO (0.05 mol%), BaO (0.005 mol%), Al2O3 (0.5 mol%), MgO (0.2 mol%), B2O3 (0.05 mol%), In2O3 (0.005 mol%), La2O3 (0.05 mol%), Y2O3 (0.02 mol%), Ga2O3 (0.02 mol%), SiO2 (0.3 mol%), and TiO2 (0.3 mol%).

[0035] Put the above materials together into a nylon jar, use zirconium oxide balls or stainless steel balls, and wet grind them in a planetary ball mill with water as the medium, with a rotation speed of 550rpm, a material-ball ratio of 10:1, and ball milling for 9 hours; dry the slurry at 120℃ and calcine it at 450℃ for 2 hours to obtain a composite powder; then add 10wt% of PVA binder and granulate it manually. The granulated powder is pressed with a pressure of 150Mpa, and then a green body with a diameter of 10mm is pressed out; after molding, the binder is removed at 500℃ for 5 hours, and under the protection of a mixed atmosphere composed of nitrogen and carbon monoxide, the ceramic green body is raised from room temperature to 1200℃ at 5℃ / min, kept warm for 3 hours, and then cooled with the furnace, and silver electrodes are brushed to obtain zinc oxide varistors.

[0036] The varistor of zinc oxide obtained in Example 1 has a varistor voltage of 374 V / mm, a nonlinear coefficient of 16, and a leakage current of 67 μA. After the AC aging test, the varistor voltage is 350 V / mm, the change rate is 6.4%, the nonlinear coefficient is 10, the leakage current is 86 μA, and the aging coefficient K is 0. T=1.5. After the DC aging test, the varistor voltage is 341V / mm, the change rate is 8.8%, the nonlinear coefficient is 8, the leakage current is 102μA, and the aging coefficient K T =2.8.

[0037] Example 2

[0038] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 2 includes: ZnO (95.86mol%), CaCO3 (1.5mol%), Co3O4 (0.1mol%), Cr2O3 (1.25mol%), Sb2O3 (0.05mol%), MnO2 (0.5mol%), NiO (0.05mol%), BaO (0.01mol%), Al2O3 (0.4mol%), MgO (0.005mol%), B2O3 (0.005mol%), In2O3 (0.005mol%), La2O3 (0.2mol%), Y2O3 (0.005mol%), Ga2O3 (0.02mol%), SiO2 (0.02mol%), and TiO2 (0.02mol%).

[0039] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 2 is similar to that in Example 1. The varistor of zinc oxide obtained in Example 2 has a varistor voltage of 400 V / mm, a nonlinear coefficient of 18, and a leakage current of 55 μA. After the AC aging test, the varistor voltage is 379 V / mm, the change rate is 5.3%, the nonlinear coefficient is 13, the leakage current is 70 μA, and the aging coefficient K is 0. T =1.2. After the DC aging test, the varistor voltage is 367V / mm, the change rate is 8.3%, the nonlinear coefficient is 10, the leakage current is 89μA, and the aging coefficient K T =2.7.

[0040] Example 3

[0041] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 3 includes: ZnO (95.741 mol%), CaCO3 (1.15 mol%), Co3O4 (0.5 mol%), Cr2O3 (2 mol%), Sb2O3 (0.05 mol%), MnO2 (0.01 mol%), NiO (0.006 mol%), BaO (0.01 mol%), Al2O3 (0.3 mol%), MgO (0.006 mol%), B2O3 (0.006 mol%), In2O3 (0.006 mol%), La2O3 (0.1 mol%), Y2O3 (0.01 mol%), Ga2O3 (0.005 mol%), SiO2 (0.05 mol%), and TiO2 (0.05 mol%).

[0042] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 3 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 3 is 362V / mm, the nonlinear coefficient is 25, and the leakage current is 68μA. After the AC aging test, the varistor voltage is 333V / mm, the change rate is 8.0%, the nonlinear coefficient is 17, the leakage current is 80μA, and the aging coefficient K is 0. T =0.9. After the DC aging test, the varistor voltage is 326V / mm, the change rate is 9.9%, the nonlinear coefficient is 12, the leakage current is 99μA, and the aging coefficient K T =2.5.

[0043] Example 4

[0044] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 4 includes: ZnO (88.94 mol%), CaCO3 (0.01 mol%), Co3O4 (0.05 mol%), Cr2O3 (2 mol%), MnO2 (2 mol%), NiO (0.5 mol%), BaO (1 mol%), Al2O3 (0.5 mol%), MgO (2 mol%), B2O3 (0.5 mol%), In2O3 (0.25 mol%), La2O3 (1 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.25 mol%), SiO2 (0.25 mol%), and TiO2 (0.25 mol%).

[0045] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 4 is based on Example 1. The varistor voltage of the zinc oxide varistor obtained in Example 4 is 444V / mm, the nonlinear coefficient is 20, and the leakage current is 73μA. After the AC aging test, the varistor voltage is 415V / mm, the change rate is 6.5%, the nonlinear coefficient is 11, the leakage current is 92μA, and the aging coefficient K is 2.5. T =1.50. After the DC aging test, the varistor voltage is 400V / mm, the change rate is 9.9%, the nonlinear coefficient is 8, the leakage current is 100μA, and the aging coefficient K T =2.13.

[0046] Example 5

[0047] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 5 includes: ZnO (91.5 mol%), CaCO3 (0.5 mol%), Co3O4 (0.5 mol%), Cr2O3 (1.5 mol%), Sb2O3 (0.5 mol%), NiO (0.5 mol%), BaO (0.1 mol%), Al2O3 (0.4 mol%), MgO (1.5 mol%), B2O3 (0.5 mol%), In2O3 (0.25 mol%), La2O3 (1 mol%), Y2O3 (0.2 mol%), Ga2O3 (0.05 mol%), SiO2 (0.5 mol%), and TiO2 (0.5 mol%).

[0048] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 5 is based on Example 1. The varistor obtained in Example 5 has a varistor voltage of 405 V / mm, a nonlinear coefficient of 15, and a leakage current of 75 μA. After the AC aging test, the varistor voltage is 388 V / mm, the change rate is 4.2%, the nonlinear coefficient is 10, the leakage current is 90 μA, and the aging coefficient K is 2.34. T =1.19. After the DC aging test, the varistor voltage is 379V / mm, the change rate is 6.4%, the nonlinear coefficient is 7, the leakage current is 99μA, and the aging coefficient K T =1.90.

[0049] Example 6

[0050] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 6 includes: ZnO (92.8 mol%), CaCO3 (0.1 mol%), Co3O4 (0.05 mol%), Cr2O3 (2 mol%), Sb2O3 (0.5 mol%), MnO2 (1 mol%), BaO (0.2 mol%), Al2O3 (0.5 mol%), MgO (1 mol%), B2O3 (0.05 mol%), In2O3 (0.2 mol%), La2O3 (0.5 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.1 mol%), SiO2 (0.25 mol%), and TiO2 (0.25 mol%).

[0051] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 6 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 6 is 377V / mm, the nonlinear coefficient is 17, and the leakage current is 68μA. After the AC aging test, the varistor voltage is 355V / mm, the change rate is 5.8%, the nonlinear coefficient is 13, the leakage current is 83μA, and the aging coefficient K is 0.1. T =1.19. After the DC aging test, the varistor voltage is 340V / mm, the change rate is 9.8%, the nonlinear coefficient is 9, the leakage current is 98μA, and the aging coefficient K T =2.37.

[0052] Table 1 lists the raw material composition and performance data of ZnO varistors prepared in Examples 1-6:

[0053] Example 7

[0054] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 7 includes: ZnO (91.35 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (2 mol%), Sb2O3 (0.5 mol%), MnO2 (1.5 mol%), NiO (0.1 mol%), BaO (0.5 mol%), Al2O3 (0.5 mol%), MgO (1 mol%), B2O3 (0.05 mol%), In2O3 (0.25 mol%), Ga2O3 (0.05 mol%), SiO2 (0.3 mol%), and TiO2 (0.4 mol%).

[0055] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 7 is based on Example 1. The varistor voltage of the zinc oxide varistor obtained in Example 7 is 303 V / mm, the nonlinear coefficient is 22, and the leakage current is 59 μA. After the AC aging test, the varistor voltage is 290 V / mm, the change rate is 4.3%, the nonlinear coefficient is 14, the leakage current is 80 μA, and the aging coefficient K is 0. T =1.66. After the DC aging test, the varistor voltage is 278V / mm, the change rate is 8.3%, the nonlinear coefficient is 10, the leakage current is 99μA, and the aging coefficient K T =3.16.

[0056] Example 8

[0057] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 8 includes: ZnO (92.2 mol%), CaCO3 (2.5 mol%), Co3O4 (0.2 mol%), Cr2O3 (1 mol%), Sb2O3 (0.05 mol%), MnO2 (0.5 mol%), BaO (0.5 mol%), Al2O3 (0.05 mol%), MgO (1 mol%), B2O3 (0.5 mol%), In2O3 (0.05 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), SiO2 (0.4 mol%), and TiO2 (0.5 mol%).

[0058] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 8 is based on Example 1. The varistor of zinc oxide obtained in Example 8 has a varistor voltage of 300 V / mm, a nonlinear coefficient of 20, and a leakage current of 53 μA. After the AC aging test, the varistor voltage is 284 V / mm, the change rate is 5.3%, the nonlinear coefficient is 15, the leakage current is 70 μA, and the aging coefficient K is 0. T =1.34. After the DC aging test, the varistor voltage is 273V / mm, the change rate is 9.0%, the nonlinear coefficient is 11, the leakage current is 80μA, and the aging coefficient K T =2.13.

[0059] Example 9

[0060] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 9 includes: ZnO (93.09 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1.5 mol%), Sb2O3 (0.5 mol%), MnO2 (1 mol%), NiO (0.01 mol%), B2O3 (0.5 mol%), In2O3 (0.3 mol%), La2O3 (0.5 mol%), Ga2O3 (0.05 mol%), SiO2 (0.05 mol%), and TiO2 (1 mol%).

[0061] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 9 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 9 is 340V / mm, the nonlinear coefficient is 31, and the leakage current is 36μA. After the AC aging test, the varistor voltage is 319V / mm, the change rate is 6.2%, the nonlinear coefficient is 26, the leakage current is 48μA, and the aging coefficient K is 0. T =0.95. After the DC aging test, the varistor voltage is 307V / mm, the change rate is 9.7%, the nonlinear coefficient is 20, the leakage current is 56μA, and the aging coefficient K T =1.58.

[0062] Example 10

[0063] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 10 includes: ZnO (93.55 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.05 mol%), MnO2 (0.5 mol%), NiO (0.05 mol%), BaO (0.5 mol%), Al2O3 (0.5 mol%), MgO (0.5 mol%), B2O3 (0.3 mol%), In2O3 (0.05 mol%), La2O3 (0.5 mol%), and TiO2 (1 mol%).

[0064] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 10 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 10 is 322V / mm, the nonlinear coefficient is 20, and the leakage current is 47μA. After the AC aging test, the varistor voltage is 303V / mm, the change rate is 5.9%, the nonlinear coefficient is 18, the leakage current is 58μA, and the aging coefficient K is 0.1. T=0.87. After the DC aging test, the varistor voltage is 300V / mm, the change rate is 6.8%, the nonlinear coefficient is 17, the leakage current is 60μA, and the aging coefficient K T =1.03.

[0065] Embodiment 11

[0066] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 19 includes: ZnO (93.9 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), BaO (0.5 mol%), MgO (0.5 mol%), B2O3 (0.5 mol%), In2O3 (0.05 mol%), La2O3 (0.5 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.05 mol%), and SiO2 (1 mol%).

[0067] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 11 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 11 is 320V / mm, the nonlinear coefficient is 25, and the leakage current is 43μA. After the AC aging test, the varistor voltage is 316V / mm, the change rate is 1.3%, the nonlinear coefficient is 23, the leakage current is 47μA, and the aging coefficient K is 0. T =0.32. After the DC aging test, the varistor voltage is 312V / mm, the change rate is 2.5%, the nonlinear coefficient is 21, the leakage current is 51μA, and the aging coefficient K T =0.63.

[0068] Example 12

[0069] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 12 includes: ZnO (94.95 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.5 mol%), Al2O3 (0.5 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.05 mol%), and SiO2 (0.5 mol%).

[0070] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 12 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 12 is 302V / mm, the nonlinear coefficient is 20, and the leakage current is 46μA. After the AC aging test, the varistor voltage is 289V / mm, the change rate is 4.3%, the nonlinear coefficient is 14, the leakage current is 58μA, and the aging coefficient K is 0. T =0.95. After the DC aging test, the varistor voltage is 286V / mm, the change rate is 5.3%, the nonlinear coefficient is 11, the leakage current is 61μA, and the aging coefficient K T =1.19.

[0071] Table 2 lists the raw material composition and performance data of ZnO varistors prepared in Examples 7-12:

[0072] Example 13

[0073] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 13 includes: ZnO (94.5 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Al2O3 (0.5 mol%), La2O3 (0.5 mol%), Y2O3 (0.3 mol%), Ga2O3 (0.25 mol%), and SiO2 (0.5 mol%).

[0074] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 13 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 13 is 290V / mm, the nonlinear coefficient is 29, and the leakage current is 48μA. After the AC aging test, the varistor voltage is 278V / mm, the change rate is 4.1%, the nonlinear coefficient is 20, the leakage current is 60μA, and the aging coefficient K is 2. T =0.95. After the DC aging test, the varistor voltage is 276V / mm, the change rate is 4.8%, the nonlinear coefficient is 19, the leakage current is 62μA, and the aging coefficient K T =1.11.

[0075] Embodiment 14

[0076] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 14 includes: ZnO (95.2 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), BaO (0.5 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.25 mol%), and SiO2 (0.5 mol%).

[0077] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 14 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 14 is 312V / mm, the nonlinear coefficient is 30, and the leakage current is 36μA. After the AC aging test, the varistor voltage is 310V / mm, the change rate is 0.6%, the nonlinear coefficient is 28, the leakage current is 38μA, and the aging coefficient K is 0.1. T =0.16. After the DC aging test, the varistor voltage is 307V / mm, the change rate is 1.6%, the nonlinear coefficient is 24, the leakage current is 45μA, and the aging coefficient K T =0.71.

[0078] Embodiment 15

[0079] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 23 includes: ZnO (94.85 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), BaO (0.05 mol%), Al2O3 (0.5 mol%), MgO (0.05 mol%), B2O3 (0.5 mol%), SiO2 (0.1 mol%), and TiO2 (0.05 mol%).

[0080] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 15 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 15 is 296V / mm, the nonlinear coefficient is 24, and the leakage current is 40μA. After the AC aging test, the varistor voltage is 282V / mm, the change rate is 4.7%, the nonlinear coefficient is 20, the leakage current is 50μA, and the aging coefficient K is 2. T=0.79. After the DC aging test, the varistor voltage is 280V / mm, the change rate is 5.4%, the nonlinear coefficient is 18, the leakage current is 20μA, and the aging coefficient K T =1.58.

[0081] Example 16

[0082] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 16 includes: ZnO (95.75 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), NiO (0.05 mol%), MgO (0.2 mol%), B2O3 (0.5 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.25 mol%), SiO2 (0.1 mol%), and TiO2 (0.1 mol%).

[0083] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 16 refers to Example 1. The varistor of zinc oxide obtained in Example 16 has a varistor voltage of 399 V / mm, a nonlinear coefficient of 31, and a leakage current of 26 μA. After the AC aging test, the varistor voltage is 397 V / mm, the change rate is 0.5%, the nonlinear coefficient is 28, the leakage current is 29 μA, and the aging coefficient K is 0.1. T =0.24. After the DC aging test, the varistor voltage is 394V / mm, the change rate is 1.3%, the nonlinear coefficient is 25, the leakage current is 31μA, and the aging coefficient K T =0.40.

[0084] Embodiment 17

[0085] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 17 includes: ZnO (96.2 mol%), CaCO3 (0.5 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), BaO (0.3 mol%), Al2O3 (0.5 mol%), MgO (0.05 mol%), B2O3 (0.25 mol%), and In2O3 (0.25 mol%).

[0086] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 17 is based on Example 1. The varistor voltage of the zinc oxide varistor obtained in Example 17 is 367V / mm, the nonlinear coefficient is 19, and the leakage current is 51μA. After the AC aging test, the varistor voltage is 349V / mm, the change rate is 4.9%, the nonlinear coefficient is 14, the leakage current is 58μA, and the aging coefficient K is 0. T =0.55. After the DC aging test, the varistor voltage is 346V / mm, the change rate is 5.7%, the nonlinear coefficient is 11, the leakage current is 61μA, and the aging coefficient K T =0.79.

[0087] Embodiment 18

[0088] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 18 includes: ZnO (95.45 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.4 mol%), NiO (0.05 mol%), BaO (0.1 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.2 mol%), SiO2 (0.25 mol%), and TiO2 (0.25 mol%).

[0089] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 18 refers to Example 1. The varistor of zinc oxide obtained in Example 18 has a varistor voltage of 315 V / mm, a nonlinear coefficient of 21, and a leakage current of 46 μA. After the AC aging test, the varistor voltage is 301 V / mm, the change rate is 4.4%, the nonlinear coefficient is 14, the leakage current is 56 μA, and the aging coefficient K is 0. T =0.79. After the DC aging test, the varistor voltage is 295V / mm, the change rate is 6.3%, the nonlinear coefficient is 11, the leakage current is 61μA, and the aging coefficient K T =1.19.

[0090] Table 3 lists the raw material composition and performance data of ZnO varistors prepared in Examples 13-18:

[0091] Embodiment 19

[0092] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 19 includes: ZnO (95.7 mol%), CaCO3 (2 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), B2O3 (0.05 mol%), In2O3 (0.05 mol%), La2O3 (0.4 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.05 mol%), SiO2 (0.1 mol%), and TiO2 (0.1 mol%).

[0093] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 19 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 19 is 267V / mm, the nonlinear coefficient is 39, and the leakage current is 31μA. After the AC aging test, the varistor voltage is 259V / mm, the change rate is 3.0%, the nonlinear coefficient is 34, the leakage current is 38μA, and the aging coefficient K is 2.0. T =0.55. After the DC aging test, the varistor voltage is 246V / mm, the change rate is 7.9%, the nonlinear coefficient is 30, the leakage current is 41μA, and the aging coefficient K T =0.79.

[0094] Embodiment 20

[0095] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 20 includes: ZnO (96.45 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), Al2O3 (0.5 mol%), and Y2O3 (0.05 mol%).

[0096] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 20 refers to Example 1. The varistor voltage of the zinc oxide varistor obtained in Example 20 is 278V / mm, the nonlinear coefficient is 20, and the leakage current is 44μA. After the AC aging test, the varistor voltage is 270V / mm, the change rate is 2.9%, the nonlinear coefficient is 15, the leakage current is 56μA, and the aging coefficient K is 2.9%. T =0.95. After the DC aging test, the varistor voltage is 266V / mm, the change rate is 4.3%, the nonlinear coefficient is 12, the leakage current is 59μA, and the aging coefficient K T =1.19.

[0097] Embodiment 21

[0098] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 21 includes: ZnO (95.95 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), and Ga2O3 (0.5 mol%).

[0099] The preparation process of the novel AC and DC high-stability ZnO varistor in this embodiment 21 refers to that in embodiment 1. The varistor voltage of the zinc oxide varistor obtained in this embodiment 21 is 310V / mm, the nonlinear coefficient is 30, and the leakage current is 36μA. After the AC aging test, the varistor voltage is 310V / mm, the change rate is 0%, the nonlinear coefficient is 30, the leakage current is 37μA, and the aging coefficient K is 0. T =0.16. After the DC aging test, the varistor voltage is 309V / mm, the change rate is 0.3%, the nonlinear coefficient is 29, the leakage current is 39μA, and the aging coefficient K T =0.24.

[0100] Embodiment 22

[0101] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 22 includes: ZnO (96.2 mol%), CaCO3 (1.5 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.25 mol%), and SiO2 (0.25 mol%).

[0102] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 22 refers to Example 1. The varistor voltage of the zinc oxide varistor obtained in Example 22 is 386V / mm, the nonlinear coefficient is 32, and the leakage current is 40μA. After the AC aging test, the varistor voltage is 383V / mm, the change rate is 0.8%, the nonlinear coefficient is 28, the leakage current is 44μA, and the aging coefficient K is 0.1. T =0.32. After the DC aging test, the varistor voltage is 379V / mm, the change rate is 1.8%, the nonlinear coefficient is 25, the leakage current is 49μA, and the aging coefficient K T =0.71.

[0103] Embodiment 23

[0104] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 23 includes: ZnO (97.5 mol%), CaCO3 (0.5 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), Ga2O3 (0.1 mol%), SiO2 (0.2 mol%), and TiO2 (0.2 mol%).

[0105] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 23 is similar to that in Example 1. The varistor of zinc oxide obtained in Example 23 has a varistor voltage of 300 V / mm, a nonlinear coefficient of 34, and a leakage current of 23 μA. After the AC aging test, the varistor voltage is 296 V / mm, the change rate is 1.3%, the nonlinear coefficient is 31, the leakage current is 28 μA, and the aging coefficient K is 0. T =0.40. After the DC aging test, the varistor voltage is 290V / mm, the change rate is 3.3%, the nonlinear coefficient is 29, the leakage current is 31μA, and the aging coefficient K T =0.63.

[0106] Embodiment 24

[0107] The raw material composition of the new AC and DC high-stability ZnO varistor in this embodiment 24 includes: ZnO (97 mol%), CaCO3 (1.5 mol%), Co3O4 (0.5 mol%), and Cr2O3 (1 mol%).

[0108] The preparation process of the novel AC and DC high-stability ZnO varistor in Example 24 refers to Example 1. The varistor of zinc oxide obtained in Example 24 has a varistor voltage of 311 V / mm, a nonlinear coefficient of 38, and a leakage current of 16 μA. After the AC aging test, the varistor voltage is 311 V / mm, the change rate is 0%, the nonlinear coefficient is 38, the leakage current is 16 μA, and the aging coefficient K is 0. T = 0. After the DC aging test, the varistor voltage is 310V / mm, the change rate is 0.3%, the nonlinear coefficient is 36, the leakage current is 17μA, and the aging coefficient K T =0.08.

[0109] Table 4 lists the raw material composition and performance data of ZnO varistors prepared in Examples 19-24:

[0110] Comparative Example 1

[0111] The raw material composition of the ZnO varistor in this comparative example 1 includes: ZnO (87.34 mol%), CaCO3 (3 mol%), Co3O4 (2 mol%), Cr2O3 (1 mol%), Sb2O3 (1 mol%), MnO2 (1 mol%), NiO (0.5 mol%), BaO (0.1 mol%), Al2O3 (1 mol%), MgO (1 mol%), B2O3 (0.5 mol%), In2O3 (0.01 mol%), La2O3 (1 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.01 mol%), SiO2 (0.01 mol%), and TiO2 (0.03 mol%).

[0112] The preparation process of the ZnO varistor in this comparative example 1 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 1 has a varistor voltage of 467V / mm, a nonlinear coefficient of 14, and a leakage current of 79μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 419V / mm, the change rate is 10.3%, the nonlinear coefficient is 8, the leakage current is 103μA, and the aging coefficient K T =1.90. After the DC aging test, the varistor voltage is 398V / mm, the change rate is 14.8%, the nonlinear coefficient is 5, the leakage current is 121μA, and the aging coefficient K T =3.32.

[0113] Comparative Example 2

[0114] The raw material composition of the ZnO varistor in this comparative example 2 includes: ZnO (85.15 mol%), CaCO3 (0.5 mol%), Co3O4 (1.5 mol%), Cr2O3 (2 mol%), Sb2O3 (1.5 mol%), MnO2 (2.5 mol%), NiO (0.5 mol%), BaO (0.3 mol%), Al2O3 (1.5 mol%), MgO (0.5 mol%), B2O3 (0.5 mol%), In2O3 (0.05 mol%), La2O3 (1 mol%), Y2O3 (1 mol%), Ga2O3 (0.5 mol%), SiO2 (0.5 mol%), and TiO2 (0.5 mol%).

[0115] The preparation process of the ZnO varistor in this comparative example 2 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 2 has a varistor voltage of 223V / mm, a nonlinear coefficient of 18, and a leakage current of 80μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 201V / mm, the change rate is 9.9%, the nonlinear coefficient is 14, the leakage current is 97μA, and the aging coefficient KT =1.34. After the DC aging test, the varistor voltage is 196V / mm, the change rate is 12.1%, the nonlinear coefficient is 10, the leakage current is 104μA, and the aging coefficient K T =1.90.

[0116] Comparative Example 3

[0117] The raw material composition of the ZnO varistor in this comparative example 3 includes: ZnO (91.3 mol%), CaCO3 (0.05 mol%), Co3O4 (1 mol%), Cr2O3 (0.05 mol%), Sb2O3 (0.5 mol%), MnO2 (1 mol%), NiO (0.5 mol%), Al2O3 (1.5 mol%), MgO (1 mol%), B2O3 (0.5 mol%), In2O3 (0.05 mol%), La2O3 (1 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.05 mol%), SiO2 (0.5 mol%), and TiO2 (0.5 mol%).

[0118] The preparation process of the ZnO varistor in this comparative example 3 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 4 has a varistor voltage of 366V / mm, a nonlinear coefficient of 22, and a leakage current of 65μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 341V / mm, the change rate is 6.8%, the nonlinear coefficient is 16, the leakage current is 88μA, and the aging coefficient K T =1.82. After the DC aging test, the varistor voltage is 317V / mm, the change rate is 13.4%, the nonlinear coefficient is 7, the leakage current is 109μA, and the aging coefficient K T =3.48.

[0119] Comparative Example 4

[0120] The raw material composition of the ZnO varistor in this comparative example 4 includes: ZnO (90.35 mol%), CaCO3 (1 mol%), Co3O4 (2 mol%), Cr2O3 (1 mol%), Sb2O3 (0.5 mol%), NiO (0.1 mol%), BaO (0.5 mol%), MgO (1 mol%), B2O3 (1 mol%), In2O3 (0.05 mol%), La2O3 (1 mol%), Y2O3 (0.5 mol%), Ga2O3 (0.5 mol%), SiO2 (0.5 mol%), and TiO2 (0.5 mol%).

[0121] The preparation process of the ZnO varistor in this comparative example 4 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 4 has a varistor voltage of 279V / mm, a nonlinear coefficient of 23, and a leakage current of 57μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 260V / mm, the change rate is 6.8%, the nonlinear coefficient is 19, the leakage current is 68μA, and the aging coefficient K T =0.87. After the DC aging test, the varistor voltage is 247V / mm, the change rate is 11.5%, the nonlinear coefficient is 12, the leakage current is 79μA, and the aging coefficient K T =1.74.

[0122] Comparative Example 5

[0123] The raw material composition of the ZnO varistor in this comparative example 5 includes: ZnO (91.25 mol%), CaCO3 (0.5 mol%), Co3O4 (0.5 mol%), Cr2O3 (0.5 mol%), Sb2O3 (0.5 mol%), MnO2 (1 mol%), NiO (0.1 mol%), BaO (0.5 mol%), Al2O3 (3 mol%), In2O3 (0.5 mol%), La2O3 (1 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.05 mol%), SiO2 (0.05 mol%), and TiO2 (0.5 mol%).

[0124] The preparation process of the ZnO varistor in this comparative example 5 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 5 has a varistor voltage of 332V / mm, a nonlinear coefficient of 17, and a leakage current of 83μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 304V / mm, the change rate is 8.4%, the nonlinear coefficient is 10, the leakage current is 99μA, and the aging coefficient K is 2.34V / mm. T =1.26. After the DC aging test, the varistor voltage is 291V / mm, the change rate is 12.3%, the nonlinear coefficient is 6, the leakage current is 115μA, and the aging coefficient K T =2.53.

[0125] Comparative Example 6

[0126] The raw material composition of the ZnO varistor in this comparative example 6 includes: ZnO (90.15 mol%), CaCO3 (2 mol%), Co3O4 (2 mol%), Cr2O3 (2 mol%), Sb2O3 (0.5 mol%), MnO2 (1 mol%), NiO (0.05 mol%), BaO (0.05 mol%), Al2O3 (0.3 mol%), MgO (0.5 mol%), B2O3 (0.5 mol%), In2O3 (0.25 mol%), La2O3 (0.4 mol%), Y2O3 (0.25 mol%), and Ga2O3 (0.05 mol%).

[0127] The preparation process of the ZnO varistor in this comparative example 6 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 6 has a varistor voltage of 298V / mm, a nonlinear coefficient of 22, and a leakage current of 67μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 270V / mm, the change rate is 9.4%, the nonlinear coefficient is 16, the leakage current is 89μA, and the aging coefficient K T =1.74. After the DC aging test, the varistor voltage is 260V / mm, the change rate is 12.8%, the nonlinear coefficient is 13, the leakage current is 99μA, and the aging coefficient K T =2.53.

[0128] Table 5 lists the raw material composition and performance data of ZnO varistors prepared in Comparative Examples 1-6:

[0129] Comparative Example 7

[0130] The raw material composition of the ZnO varistor in this comparative example 7 includes: ZnO (90 mol%), CaCO3 (1.5 mol%), Co3O4 (1 mol%), Cr2O3 (2 mol%), BaO (0.5 mol%), Al2O3 (2 mol%), MgO (0.5 mol%), B2O3 (1 mol%), In2O3 (0.05 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.5 mol%), SiO2 (0.4 mol%), and TiO2 (0.5 mol%).

[0131] The preparation process of the ZnO varistor in this comparative example 7 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 7 has a varistor voltage of 333V / mm, a nonlinear coefficient of 18, and a leakage current of 64μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 310V / mm, the change rate is 6.9%, the nonlinear coefficient is 14, the leakage current is 85μA, and the aging coefficient K T =1.66. After the DC aging test, the varistor voltage is 297V / mm, the change rate is 10.8%, the nonlinear coefficient is 9, the leakage current is 100μA, and the aging coefficient K T =2.85.

[0132] Comparative Example 8

[0133] The raw material composition of the ZnO varistor in this comparative example 8 includes: ZnO (91.9 mol%), CaCO3 (3 mol%), Co3O4 (0.4 mol%), Cr2O3 (0.05 mol%), Sb2O3 (1 mol%), MnO2 (0.5 mol%), NiO (0.05 mol%), BaO (0.5 mol%), Al2O3 (1 mol%), MgO (0.5 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.05 mol%), SiO2 (0.5 mol%), and TiO2 (0.5 mol%).

[0134] The preparation process of the ZnO varistor in this comparative example 8 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 8 has a varistor voltage of 319V / mm, a nonlinear coefficient of 32, and a leakage current of 46μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 299V / mm, the change rate is 6.3%, the nonlinear coefficient is 26, the leakage current is 58μA, and the aging coefficient K T =0.95. After the DC aging test, the varistor voltage is 280V / mm, the change rate is 12.3%, the nonlinear coefficient is 20, the leakage current is 66μA, and the aging coefficient K T =1.58.

[0135] Comparative Example 9

[0136] The raw material composition of the ZnO varistor in this comparative example 9 includes: ZnO (94.95 mol%), CaCO3 (1 mol%), Co3O4 (1.5 mol%), Cr2O3 (1 mol%), Sb2O3 (0.25 mol%), MnO2 (0.2 mol%), NiO (0.05 mol%), Al2O3 (0.5 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), and Ga2O3 (0.5 mol%).

[0137] The preparation process of the ZnO varistor in this comparative example 9 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 9 has a varistor voltage of 350V / mm, a nonlinear coefficient of 25, and a leakage current of 45μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 339V / mm, the change rate is 3.1%, the nonlinear coefficient is 20, the leakage current is 54μA, and the aging coefficient K T =0.71. After the DC aging test, the varistor voltage is 301V / mm, the change rate is 14%, the nonlinear coefficient is 15, the leakage current is 73μA, and the aging coefficient K T =1.42.

[0138] Comparative Example 10

[0139] The raw material composition of the ZnO varistor in this comparative example 10 includes: ZnO (95.95 mol%), CaCO3 (1 mol%), Co3O4 (0.5 mol%), Cr2O3 (1 mol%), La2O3 (0.5 mol%), Y2O3 (0.05 mol%), Ga2O3 (0.5 mol%), and SiO2 (0.5 mol%).

[0140] The preparation process of the ZnO varistor in this comparative example 10 refers to Example 1. The varistor of the zinc oxide varistor obtained in this comparative example 10 has a varistor voltage of 333V / mm, a nonlinear coefficient of 22, and a leakage current of 53μA. After the AC aging test, the varistor voltage of the zinc oxide varistor is 309V / mm, the change rate is 7.2%, the nonlinear coefficient is 19, the leakage current is 58μA, and the aging coefficient K T =0.40. After the DC aging test, the varistor voltage is 296V / mm, the change rate is 11.1%, the nonlinear coefficient is 15, the leakage current is 65μA, and the aging coefficient K T =0.95.

[0141] Table 6 lists the raw material composition and performance data of ZnO varistors prepared in Comparative Examples 7-10:

Claims

1. A new type of AC and DC high stability ZnO varistor, characterized in that: The ZnO varistor is composed of ZnO, a compound containing Cr and a modified dopant; wherein the content of ZnO is 74-99.995 mol%, the content of Cr is 0.005-4 mol%, the content of the modified dopant is 0-22 mol%, and the sum of the molar contents of each component is 100 mol%; the modified dopant is composed of a compound containing at least one of Sb, Co, Ca, Mn, Ni, Ba, Al, Mg, B, In, La, Y, Ga, Si and Ti.

2. The ZnO varistor according to claim 1, characterized in that: In the modified dopant, the contents of each element are: Ca: 0-4mol%, Co: 0-2mol%, Sb: 0-1.5mol%, Mn: 0-4mol%, Ni: 0-1mol%, Ba: 0-1mol%, Al: 0-1.5mol%, Mg: 0-2mol%, B: 0-1mol%, In: 0-0.5mol%, La: 0-2mol%, Y: 0-1mol%, Ga: 0-0.5mol%, Si: 0-1mol%, Ti: 0-1mol%.

3. The ZnO varistor according to claim 1 or 2, characterized in that: The nonlinear coefficient of the ZnO varistor is α≥8, and the leakage current I L ≤100μA; At 80% V 1mA After aging for 160 hours at 135°C under AC voltage, the varistor voltage change rate does not exceed 10%, and the leakage current I L ≤200μA, aging coefficient K T ≤100μA / h 1 / 2 ; At 80% V 1mA After aging for 160 hours at 135°C under a DC voltage, the varistor voltage change rate does not exceed 10%, and the leakage current I L ≤200μA, aging coefficient K T ≤100μA / h 1 / 2 .

4. A method for preparing a ZnO varistor according to any one of claims 1 to 3, characterized in that: include: The zinc oxide, the compound containing the Cr element and the modified dopant are mixed, ball-milled, dried and synthesized to obtain a composite powder; A binder is added to the composite powder for granulation to obtain granulated powder; the granulated powder is subjected to compression molding, debinding and sintering to obtain the ZnO varistor.

5. The preparation method according to claim 4, characterized in that: Deionized water is used as the ball milling medium, the ball milling speed is 400-1000 rpm, the ball milling time is 2-12 hours, and the material-ball ratio is 1:1-20:

1.

6. The preparation method according to claim 4 or 5, characterized in that: The drying temperature is 100-120°C.

7. The preparation method according to any one of claims 4 to 6, characterized in that: The synthesis temperature is 300-700° C. and the synthesis time is 1-4 hours.

8. The preparation method according to any one of claims 4 to 7, characterized in that: The compression molding pressure is 100-250 MPa; The debinding temperature is 350-800° C. and the time is 1-10 hours.

9. The preparation method according to any one of claims 4 to 8, characterized in that: The sintering parameters include: sintering temperature of 800-2500° C., sintering time of 1-8 hours, and heating rate of 0.5-10° C. / min.

10. The preparation method according to any one of claims 4 to 9, characterized in that: The preparation method further comprises: polishing the sintered sample and brushing a silver electrode on the surface of the sample to obtain the ZnO varistor.

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