Dysprosium acetate solution doped ZnO pressure sensitive ceramic and preparation method thereof

Abstract

The application discloses a kind of superhigh voltage gradient and nonlinear coefficient dysprosium acetate solution method doped ZnO voltage-dependent ceramic and preparation method, the ZnO voltage-dependent ceramic is composed of ZnO, voltage-dependent forming agent Bi2O3 and voltage-dependent enhancer CoO, Mn2O3, Cr2O3, SnO2, CaO, Dy (C2H3O2) 3·4H2O, wherein ZnO content is 95.15~96.04mol%, voltage-dependent forming agent Bi2O3 content is 1.0mol%, voltage-dependent enhancer Co3O4, MnO2, Cr2O3, SnO2, CaO is 0.5mol%, 0.5mol%, 0.5mol%, 1.0mol% and 0.45mol% respectively, and the content of Dy (C2H3O2) 3·4H2O is 0.01~0.9mol%.Dy (C2H3O2) 3·4H2O in the application is modifier and sintering aid.The application also provides a kind of preparation method of the above-mentioned superhigh voltage gradient and nonlinear coefficient ZnO voltage-dependent ceramic.The application solves the problem that existing high-voltage voltage-dependent ceramic preparation method is difficult to obtain high-voltage voltage-dependent ceramic with poor performance, and the preparation method of the application has the advantages of simple process, low energy consumption, green environmental protection and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of ceramic production, and particularly relates to a ZnO voltage-sensitive ceramic with an ultrahigh voltage gradient and a nonlinear coefficient and a preparation method. BACKGROUND

[0002] Pure ZnO ceramic does not have nonlinear characteristics, and needs to be doped with a proper amount of a voltage-sensitive forming agent (mainly Bi2O3, Pr6O 11 and V2O5) and a voltage-sensitive enhancer (mainly Co2O3, Mn2O3, SnO2, Cr2O3, and other oxides) to exhibit excellent nonlinear electrical characteristics in a macroscopic manner. Therefore, ZnO voltage-sensitive ceramic, with its high nonlinear coefficient, excellent energy resistance, and low raw material cost, has become an ideal choice for limiting overvoltage in power systems. They are widely used in AC and DC lines and power equipment to effectively suppress transient voltage and absorb surges, and at the same time, protect sensitive electronic equipment from voltage fluctuations or mutations.

[0003] It is reported that Toshiba in Japan has successfully commercialized a high-voltage gradient ZnO ceramic resistor sheet with a voltage gradient as high as 1000 V / mm, and its leakage current is as low as 3 mu A or less. The application of this resistor sheet in a 500 kV gas insulated switchgear (GIS) arrester shows significant advantages. Compared with the traditional arrester of the same type with a voltage gradient of 600 V / mm, the arrester using this high-voltage gradient ZnO resistor sheet has a volume reduction of 55%, and the manufacturing cost is reduced by more than 30%. This technological progress not only improves the performance of the arrester, but also significantly reduces the production cost, making the high-voltage arrester more economical in large-scale applications. In contrast, the existing domestic mass-produced ZnO resistor sheet has a voltage gradient of less than 400 V / mm, a nonlinear coefficient of less than 60, and a leakage current of less than 20 mu A. Although these resistor sheets can meet the basic needs of domestic ultra-high voltage AC and DC arresters, there is still a significant gap in technology compared with international advanced levels. This not only affects the performance of the arrester, but also limits its promotion and use in high-end application fields.

[0004] Exploring new processes and material systems to reduce the environmental impact of production and promote the development of arresters in safety, performance, volume miniaturization, and green manufacturing. Improving the performance of ZnO voltage-sensitive resistors and optimizing their preparation process is crucial, which not only improves the performance of the arrester, but also promotes green manufacturing and reduces environmental pollution. SUMMARY

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to develop a ZnO voltage-sensitive ceramic doped with dysprosium acetate solution with an ultrahigh voltage gradient and a nonlinear coefficient.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a ZnO varistor ceramic doped by dysprosium acetate solution method, characterized in that the compositional expression of the ZnO varistor ceramic is as follows:

[0007] (100-x)mol%ZnO+1.0mol%Bi2O3+0.5mol%Co3O4+0.5mol%MnO2+0.5mol%Cr2O3+1.0mol%SnO2

[0008] +0.45 mol% CaO + x mol% Dy(C2H3O2)3·4H2O, where 0.01 ≤ x ≤ 0.9. The Dy(C2H3O2)3·4H2O can be used to improve the high voltage gradient and nonlinear coefficient of the varistor ceramic, and also as a sintering aid to assist the densification process. The voltage gradient E of the high voltage gradient and nonlinear coefficient ZnO varistor ceramic is... b The leakage current density ranges from 1364 to 5431 V / mm, with the highest nonlinear coefficient α reaching 142.16, and the leakage current density I... L The minimum is 0.07 μA / cm 2 The modified additives include: 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO and (0.01-0.9) mol% Dy(C2H3O2)3·4H2O.

[0009] A method for preparing ZnO-doped varistors using a dysprosium acetate solution method includes the following steps:

[0010] S1: Weigh out the original powders of ZnO, Bi2O3, Co3O4, MnO2, Cr2O3, SnO2, and CaO according to the stoichiometric ratio specified above, and place them in a ball mill jar. Use anhydrous ethanol zirconium balls as the medium for ball milling to thoroughly mix the powders. Remove the mixed powder, dry it, and sieve it through a 60-mesh sieve for later use. Ball mill at 380 r / min for 12 hours, and then dry it in an oven at 80℃ for at least 12 hours.

[0011] S2: Weigh out the original Dy(C2H3O2)3·4H2O powder according to the aforementioned stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for later use; the Dy element is doped into the varistor through the polar aqueous solution, which here serves to dissolve Dy(C2H3O2)3·4H2O. 2)3 The role of 4H2O is to ensure the uniform distribution of Dy elements within the ZnO matrix. The Dy(C2H3O) 2)3 ·4H2O can be used as a sintering aid to assist the densification process.

[0012] S3: The mixed powder in S1 and the mixed solution in S2 are mixed evenly by a mortar, the added amount of the mixed solution is 10-40wt% of the mixed powder, the mixed powder is fully wetted, then the mixed powder is put into a mold and is pressed under a pressure of 200-500MPa, and is heated to 200-400℃ for 30min-2h to obtain a preliminarily densified ZnO varistor ceramic embryo.

[0013] S4: The ZnO varistor ceramic embryo in S3 is put into a muffle furnace and is sintered at a sintering temperature of 700-1000℃ for 1-5h to further densify the ZnO varistor ceramic embryo to obtain a ZnO varistor ceramic product. The sintering temperature of the varistor resistor in S4 is only 700-1000℃, which is much lower than the sintering temperature of the commercial method.

[0014] Further, the mass ratio of the powder, the zirconium ball and the ball milling liquid medium in S1 is 1:10:1.5, wherein the mass ratio of the zirconium ball with a diameter of 1cm, a diameter of 0.5cm and a diameter of 0.2cm is 2:1:1, and the rotation speed of the high-energy ball mill is 380r / min.

[0015] Further, the particle size of the ZnO raw powder in S1 is about 500nm, and the particle sizes of the Bi2O3, Co3O4, MnO2, Cr2O3, SnO2 and CaO raw powders are about 100nm, about 200nm, 100-300nm, about 200nm, <250nm and <160nm, respectively.

[0016] Further, the relative density of the ZnO varistor ceramic embryo in S3 is 88%-94%.

[0017] Further, the heating rate of the sintering in S4 is 0.5-2℃ / min. Since the raw embryo prepared in S3 has a high initial density and a large internal stress, a high heating rate is easy to cause the sample to crack, so the heating rate in S4 is selected to be less than or equal to 2℃ / min, which is helpful for the slow release of the internal stress of the sample in the process of further densification.

[0018] Compared with the prior art, the present application has the following beneficial effects:

[0019] 1. Compared with the traditional sintering method, the present application innovates the sintering process by adding Dy(C2H3O2)3·4H2O sintering aid, so that the ZnO varistor ceramic is preliminarily densified at a pressure of 300MPa and a temperature of 300℃, and is further densified at a sintering temperature of 700-1000℃. During the preliminary densification, the low sintering temperature of the water molecules and part of the acetate ions in Dy(C2H3O2)3·4H2O controls the varistor ceramic grain in the micronanometer range, which is helpful for improving the voltage gradient of the varistor ceramic.

[0020] 2. In the application, Dy(C2H3O2)3·4H2O is used as an auxiliary sintering agent to promote preliminary densification. In the heating process, Dy(C2H3O2)3·4H2O first loses crystal water between 100-200℃, promoting the mass transfer in the sintering process, and then the acetate ion is decomposed into water and carbon dioxide above 200℃, further promoting plastic deformation in the sintering process.

[0021] 3. In the application, Dy(C2H3O2)3·4H2O is not only a sintering aid, but also a performance improver. By doping Dy(C2H3O2)3·4H2O, the application finally prepares ZnO pressure-sensitive ceramic material with excellent pressure-sensitive properties. With the increase of the doping amount of Dy(C2H3O2)3·4H2O, the potential gradient shows a trend of continuous increase, and the nonlinear coefficient shows a trend of first increasing and then decreasing. When the doping amount of Dy(C2H3O2)3·4H2O is 0.5mol%, the performance is best, the voltage gradient is E b 2564.37V / mm, the nonlinear coefficient a is highest as 142.16, and the leakage current density I L is minimum as 0.07μA / cm 2 . In addition, the preparation method of the application has the advantages of simple process, small energy consumption, green environmental protection, etc., and has practicality and application prospect.

[0022] 4. The addition of Dy element can effectively improve the performance of ZnO varistor ceramics. ZnO varistor ceramics are widely used in circuit protection, overvoltage protection and other fields, and their performance is affected by factors such as material composition and microstructure. The incorporation of Dy element can significantly affect the electrical properties, structural stability and varistor effect of ZnO. The specific improvement mechanism can be analyzed from the following aspects: ① Improve the crystal structure of ZnO: Dy element, as a rare earth element, has a larger ionic radius, which can effectively improve the lattice defects of ZnO and promote the uniform growth of crystal grains, thereby improving the crystal quality of ZnO. The incorporation of Dy element helps to reduce oxygen vacancies and defects in ZnO, enhancing the structural stability of the material. Dy element may replace Zn ions into the ZnO lattice to form a solid solution, thereby changing the microstructure of ZnO and further improving the electrical conductivity and varistor properties of the material. ② Adjust the electronic structure and energy band structure: The incorporation of Dy can affect the energy band structure of ZnO, especially the adjustment of the energy band gap. The d-orbital electrons of Dy interact with the conduction band of ZnO, which may lead to changes in the mobility of ZnO conduction band electrons, thereby optimizing the electrical properties of the material. This can improve the response speed and sensitivity of ZnO varistor ceramics to some extent. By adjusting the energy band structure, Dy element can improve the electronic conductivity of ZnO, especially at low voltage or high voltage difference, effectively reducing the switching voltage of ZnO varistor ceramics and enhancing its stability. ③ Improve the interface state and electrical conductivity: Dy element can change the interface state between ZnO particles, enhance the connection between particles, optimize the electron flow path, reduce electron scattering, and improve electrical conductivity. The incorporation of Dy element helps to form electron states that are conducive to electrical conductivity, which greatly improves the electrical properties of ZnO varistor ceramics, such as the nonlinear index and varistor coefficient. ④ Enhance the varistor effect of the material: In ZnO-based varistor ceramic materials, the varistor effect is determined by the relationship between the electrical conductivity of the material and the applied voltage. After the incorporation of Dy element, the nonlinear electrical conductivity and nonlinear coefficient of ZnO are usually improved, making the varistor effect of the material more pronounced. The addition of Dy element can increase the energy band gap of ZnO, reduce the excitation energy of current at high voltage, and thus enhance the varistor property of ZnO, providing stronger voltage response capability. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Relative density of ZnO varistor ceramics sintered at different sintering temperatures.

[0024] Figure 2 Voltage gradient of ZnO varistor ceramics doped with different amounts of Dy(C2H3O2)3·4H2O.

[0025] Figure 3 Nonlinear coefficient of ZnO varistor ceramics doped with different amounts of Dy(C2H3O2)3·4H2O. DETAILED DESCRIPTION

[0026] The application will be further described in details by specific examples. It should be understood that these examples are only used to illustrate the application and not used to limit the protection scope of the application.

[0027] The embodiments of the application are illustrated by specific examples below, and those skilled in the art can understand other advantages and effects of the application from the contents in the application. The application can also be applied by different embodiments, and the details in the specification can be modified or adjusted according to different views and applications without changing the basic spirit of the application.

[0028] Please note that the process equipment or device not specifically described in the following examples all adopts the conventional equipment or device in the art. All the pressure values and ranges refer to relative pressure, and the raw materials used are also the materials commonly used in the art.

[0029] Example 1

[0030] (1) 96.04 mol% of ZnO, 1.0 mol% of Bi2O3, 0.5 mol% of Co3O4, 0.5 mol% of MnO2, 0.5 mol% of Cr2O3, 1.0 mol% of SnO2, and 0.45 mol% of CaO raw powders are weighed according to the stoichiometric ratio and put into a ball mill tank, and after ball milling at a speed of 380 r / min for 12 h, the mixed powders are taken out and dried in an oven at 80℃, and finally sieved by a 60 mesh screen for standby;

[0031] (2) 0.01 mol% of Dy(C2H3O2)3·4H2O raw powder is weighed according to the stoichiometric ratio and dissolved in a polar aqueous solution to obtain a mixed solution for standby;

[0032] (3) An appropriate amount of the powder in (1) and the mixed solution in (2) are weighed, and the amount of the mixed solution is 40 wt% of the powder, and the two are mixed uniformly by a mortar, and after the powder is fully wetted, the powder is transferred into a ceramic mold, a uniaxial pressure of 500 MPa is applied by a hand tablet press, and a temperature of 400℃ is applied to the mold by a heating jacket, and after keeping warm for 30 min, a preliminary densified ZnO pressure-sensitive ceramic is obtained;

[0033] (4) The ceramic green body in (3) is put into a muffle furnace and sintered at a sintering temperature of 850℃ for 3 h with a heating rate of 2℃ / min, so as to be further densified to obtain a ZnO pressure-sensitive ceramic product.

[0034] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can achieve a relative density of 98.61% and has excellent electrical performance, and the voltage gradient Eb is 1844.63 V / mm, the nonlinear coefficient a is 54.33, the leakage current density I L is 0.25 μA / cm 2 .

[0035] Example 2:

[0036] (1) Take 95.95 mol% ZnO, 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO raw powder in stoichiometric ratio and put into a ball mill jar, take zirconium ball as medium, mill for 12 h at a speed of 380 r / min, then take out the mixed powder and dry in an oven at 80°C, finally sieve through a 60 mesh screen for standby;

[0037] (2) Take 0.1 mol% Dy(C2H3O2)3·4H2O raw powder in stoichiometric ratio and dissolve in polar aqueous solution to obtain a mixed solution for standby;

[0038] (3) Take an appropriate amount of powder in (1) and the mixed solution in (2), the amount of the mixed solution is 35wt% of the powder, mix them evenly through a mortar, then transfer the powder into a ceramic mold, apply a uniaxial pressure of 400 MPa through a hand press, and apply a temperature of 400°C to the mold through a heating jacket, then obtain a preliminary densified ZnO varistor ceramic after keeping the temperature for 1 h;

[0039] (4) Put the ceramic green body in (3) into a muffle furnace and sinter at a sintering temperature of 850°C for 3 h with a heating rate of 2°C / min, then further densify it to obtain a ZnO varistor ceramic product.

[0040] (5) Through relevant tests on the ZnO varistor ceramic product in (4), the final product can achieve a relative density of 98.58% and has excellent electrical properties, the voltage gradient E b is 2059.11 V / mm, the nonlinear coefficient a is 63.19, the leakage current density I L is 0.28 μA / cm 2 .

[0041] Example 3:

[0042] (1) Take 95.75 mol% ZnO, 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO raw powder according to the stoichiometric ratio, and put it into a ball mill tank, take zirconium alcohol balls as medium, ball mill at a speed of 380 r / min for 12 h, then take out the mixed powder and dry it in an oven at 80°C, finally sieve it with a 60 mesh sieve, ready for use;

[0043] (2) Take 0.3 mol% Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution ready for use;

[0044] (3) Take an appropriate amount of powder in (1) and the mixed solution in (2), the amount of the mixed solution is 30wt% of the powder, mix them evenly through a mortar, then put the powder into a ceramic mold, apply a uniaxial pressure of 400 MPa through a hand tablet press, and apply a temperature of 300°C to the mold through a heating jacket, and obtain a preliminary densified ZnO pressure-sensitive ceramic after keeping the temperature for 30 min;

[0045] (4) Put the ceramic green body in (3) into a muffle furnace, sinter it at a sintering temperature of 850°C for 3 h, and the heating rate is 1°C / min, so as to further densify it to obtain a ZnO pressure-sensitive ceramic product.

[0046] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can achieve a relative density of 98.53%, and has excellent electrical performance, the voltage gradient E b is 2338.84 V / mm, the nonlinear coefficient a is 88.94, and the leakage current density I L is 0.11 μA / cm 2 .

[0047] Example 4:

[0048] (1) Take 95.75 mol% ZnO, 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO raw powder according to the stoichiometric ratio, and put it into a ball mill tank, take zirconium alcohol balls as medium, ball mill at a speed of 380 r / min for 12 h, then take out the mixed powder and dry it in an oven at 80°C, finally sieve it with a 60 mesh sieve, ready for use;

[0049] (2) Take 0.5 mol% of Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby;

[0050] (3) Take an appropriate amount of powder in (1), and take the mixed solution in (2). The amount of the mixed solution is 25wt% of the powder. Mix the two through a mortar until the powder is fully wetted. Then, transfer the powder into a ceramic mold, apply a uniaxial pressure of 300 MPa through a manual tablet press, and apply a temperature of 300°C to the mold through a heating jacket. After 1h of heat preservation, a preliminarily densified ZnO pressure-sensitive ceramic is obtained;

[0051] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 850°C for 3h, and the heating rate is 1°C / min. Further densify to obtain a ZnO pressure-sensitive ceramic product.

[0052] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can achieve a relative density of 98.36%, and has excellent electrical performance. The voltage gradient E b is 2564.37 V / mm, the nonlinear coefficient a is 142.16, and the leakage current density I L is 0.07 μA / cm 2 .

[0053] Example 5:

[0054] (1) Take 95.35 mol% of ZnO, 1.0 mol% of Bi2O3, 0.5 mol% of Co3O4, 0.5 mol% of MnO2, 0.5 mol% of Cr2O3, 1.0 mol% of SnO2, and 0.45 mol% of CaO raw powder according to the stoichiometric ratio, and put them into a ball mill tank. After ball milling at a speed of 380 r / min for 12h, take out the mixed powder and dry it in an oven at 80°C. Finally, sieve it through a 60 mesh sieve for standby;

[0055] (2) Take 0.7 mol% of Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby;

[0056] (3) Take an appropriate amount of powder in (1), and take the mixed solution in (2). The amount of the mixed solution is 20wt% of the powder. Mix the two through a mortar until the powder is fully wetted. Then, transfer the powder into a ceramic mold, apply a uniaxial pressure of 300 MPa through a manual tablet press, and apply a temperature of 200°C to the mold through a heating jacket. After 1.5h of heat preservation, a preliminarily densified ZnO pressure-sensitive ceramic is obtained;

[0057] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 850°C for 3h, and the temperature rising rate is 0.5°C / min, so as to further densify it to obtain a ZnO pressure-sensitive ceramic product.

[0058] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can reach a relative density of 98.21%, and has excellent electrical performance, the voltage gradient E b is 2632.33V / mm, the nonlinear coefficient a is 95.51, the leakage current density I L is 0.12μA / cm 2 .

[0059] Example 6:

[0060] (1) Take 95.15mol% ZnO, 1.0mol% Bi2O3, 0.5mol% Co3O4, 0.5mol% MnO2, 0.5mol% Cr2O3, 1.0mol% SnO2, and 0.45mol% CaO raw powders according to the stoichiometric ratio, put them into a ball mill jar, use zirconium balls as medium, ball mill at a speed of 380r / min for 12h, then take out the mixed powder and dry it in an oven at 80°C, finally sieve it through a 60 mesh sieve for standby;

[0061] (2) Take 0.9mol% Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby;

[0062] (3) Take an appropriate amount of powder in (1), and take the mixed solution in (2), the amount of the mixed solution is 10wt% of the powder, mix them evenly through a mortar, then put the powder into a ceramic mold, apply a uniaxial pressure of 200MPa through a hand press, and apply a temperature of 200°C to the mold through a heating jacket, and keep it for 2h to obtain a preliminary densified ZnO pressure-sensitive ceramic;

[0063] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 850°C for 3h, and the temperature rising rate is 0.5°C / min, so as to further densify it to obtain a ZnO pressure-sensitive ceramic product.

[0064] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can reach a relative density of 98.32%, and has excellent electrical performance, the voltage gradient E b is 2718.69V / mm, the nonlinear coefficient a is 76.52, the leakage current density I L is 0.72μA / cm 2 .

[0065] Example 7:

[0066] (1) Take 95.55 mol% ZnO, 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO raw powder according to the stoichiometric ratio and put it into a ball mill tank, take zirconium alcohol balls as medium, mill for 12 h at a speed of 380 r / min, then take out the mixed powder and dry it in an oven at 80°C, finally sieve it through a 60 mesh screen for standby;

[0067] (2) Take 0.5 mol% Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio and dissolve it in a polar aqueous solution to obtain a mixed solution for standby;

[0068] (3) Take an appropriate amount of powder in (1) and the mixed solution in (2), the amount of the mixed solution is 25wt% of the powder, mix them evenly through a mortar, then put the powder into a ceramic mold, apply a uniaxial pressure of 300 MPa through a hand tablet press, and apply a temperature of 300°C to the mold through a heating jacket, and obtain a preliminary densified ZnO pressure-sensitive ceramic after keeping the temperature for 30 min;

[0069] (4) Put the ceramic green body in (3) into a muffle furnace and sinter it at a sintering temperature of 700°C for 5 h, with a heating rate of 1°C / min, to further densify it and obtain a ZnO pressure-sensitive ceramic product.

[0070] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can achieve a relative density of 93.07% and has excellent electrical performance, with a voltage gradient E b of 5431.66 V / mm, a nonlinearity coefficient a of 14.37, and a leakage current density I L of 17.66 μA / cm 2 .

[0071] Example 8:

[0072] (1) Take 95.55 mol% ZnO, 1.0 mol% Bi2O3, 0.5 mol% Co3O4, 0.5 mol% MnO2, 0.5 mol% Cr2O3, 1.0 mol% SnO2, 0.45 mol% CaO raw powder according to the stoichiometric ratio and put it into a ball mill tank, take zirconium alcohol balls as medium, mill for 12 h at a speed of 380 r / min, then take out the mixed powder and dry it in an oven at 80°C, finally sieve it through a 60 mesh screen for standby;

[0073] (2) Take 0.5 mol% of Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby use;

[0074] (3) Take an appropriate amount of powder in (1) and take the mixed solution in (2), the amount of the mixed solution is 25wt% of the powder, mix the two through a mortar, after the powder is fully wetted, transfer the powder into a ceramic mold, apply a uniaxial pressure of 300 MPa through a manual tablet press, and apply a temperature of 300℃ to the mold through a heating jacket, and after 1h of heat preservation, obtain a preliminary densified ZnO pressure-sensitive ceramic;

[0075] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 775℃ for 4h, and the heating rate is 1℃ / min, so as to further densify to obtain a ZnO pressure-sensitive ceramic product.

[0076] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can achieve a relative density of 96.17%, and has excellent electrical performance, the voltage gradient E b is 4025.61 V / mm, the nonlinear coefficient a is 49.21, and the leakage current density I L is 5.87 μA / cm 2 .

[0077] Example 9:

[0078] (1) Take 95.55 mol% of ZnO, 1.0 mol% of Bi2O3, 0.5 mol% of Co3O4, 0.5 mol% of MnO2, 0.5 mol% of Cr2O3, 1.0 mol% of SnO2, and 0.45 mol% of CaO raw powder according to the stoichiometric ratio, and put them into a ball mill tank, use zirconium balls as medium, and ball mill at a speed of 380 r / min for 12h, then take out the mixed powder and dry it in an oven at 80℃, finally sieve it through a 60 mesh sieve for standby use;

[0079] (2) Take 0.5 mol% of Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby use;

[0080] (3) Take an appropriate amount of powder in (1) and take the mixed solution in (2), the amount of the mixed solution is 25wt% of the powder, mix the two through a mortar, after the powder is fully wetted, transfer the powder into a ceramic mold, apply a uniaxial pressure of 300 MPa through a manual tablet press, and apply a temperature of 300℃ to the mold through a heating jacket, and after 1.5h of heat preservation, obtain a preliminary densified ZnO pressure-sensitive ceramic;

[0081] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 925℃ for 2h, and the temperature rising rate is 0.5℃ / min, so as to further densify it to obtain a ZnO pressure-sensitive ceramic product.

[0082] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can reach a relative density of 98.25%, and has excellent electrical performance, the voltage gradient E b is 1942.47V / mm, the nonlinear coefficient a is 78.17, the leakage current density I L is 0.27μA / cm 2 .

[0083] Example 10:

[0084] (1) Take 95.55mol% ZnO, 1.0mol% Bi2O3, 0.5mol% Co3O4, 0.5mol% MnO2, 0.5mol% Cr2O3, 1.0mol% SnO2, and 0.45mol% CaO raw powders according to the stoichiometric ratio, put them into a ball mill jar, use zirconium balls as medium, ball mill at a speed of 380r / min for 12h, then take out the mixed powder and dry it in an oven at 80℃, finally sieve it through a 60 mesh sieve for standby;

[0085] (2) Take 0.5mol% Dy(C2H3O2)3·4H2O raw powder according to the stoichiometric ratio, and dissolve it in a polar aqueous solution to obtain a mixed solution for standby;

[0086] (3) Take an appropriate amount of powder in (1), and take the mixed solution in (2), the amount of the mixed solution is 25wt% of the powder, mix them evenly through a mortar, then put the powder into a ceramic mold, apply a uniaxial pressure of 300MPa through a hand press, and apply a temperature of 300℃ to the mold through a heating jacket, and keep it for 2h to obtain a preliminary densified ZnO pressure-sensitive ceramic;

[0087] (4) Put the ceramic green body in (3) into a muffle furnace, sinter at a sintering temperature of 1000℃ for 1h, and the temperature rising rate is 0.5℃ / min, so as to further densify it to obtain a ZnO pressure-sensitive ceramic product.

[0088] (5) Through relevant tests on the ZnO pressure-sensitive ceramic product in (4), the final product can reach a relative density of 98.14%, and has excellent electrical performance, the voltage gradient E b is 1364.58V / mm, the nonlinear coefficient a is 56.39, the leakage current density I L is 1.83μA / cm 2 .

[0089] The ZnO varistor ceramic samples obtained from the obtained examples 1-24 were tested for performance:

[0090] Table 1 Related parameters of ZnO varistor ceramic under different conditions

[0091]

[0092]

[0093] From the above experimental results in the present application, we can find the following experimental rules:

[0094] 1. The doping of Dy element in the present application has a great influence on the key performance parameters of ZnO varistor ceramic. When the doping content is low, it can optimize the crystal structure of ZnO, improve the electrical conductivity and enhance the varistor characteristics; when the doping content is too high, it will lead to the increase of crystal defects, the enhancement of electron scattering and the weakening of varistor characteristics.

[0095] 2. The suitable sintering temperature in the present application is also very important. When the sintering temperature is too low, although the ultra-high potential gradient can be obtained, the low nonlinear coefficient and high leakage current density cannot meet the commercialization demand. This may be due to the insufficient grain growth at low sintering temperature, the insufficient diffusion effect between particles, the ineffective combination of crystal grains, the possible voids or pores in the formed ceramic body, and the influence on the density of the material; when the sintering temperature is too high, the varistor characteristics of the varistor ceramic decrease. The main reasons are the excessive sintering of particles, the grain growth, the oxidation or chemical reaction, the melting or degradation of the material, the porosity and density problems, the thermal stress, etc. In order to ensure the good performance of the varistor ceramic, sintering needs to be carried out at a suitable sintering temperature and environment to maintain its electrical characteristics to meet the requirements.

Claims

1. A dysprosium acetate solution doped ZnO varistor ceramic, characterized by, The composition expression of the ZnO pressure-sensitive ceramic is (100-x) mol% ZnO + 1.0 mol% Bi2O3 + 0.5 mol% Co3O4 + 0.5 mol% MnO2 + 0.5 mol% Cr2O3 + 1.0 mol% SnO2 + 0.45 mol% CaO + x mol% Dy(C2H3O2)3·4H2O, wherein 0.01 ≤ x ≤ 0.

9.

2. A method for preparing a dysprosium acetate solution doped ZnO varistor ceramic, characterized in that, The method comprises the following steps: S1: taking ZnO, Bi2O3, Co3O4, MnO2, Cr2O3, SnO2 and CaO raw powders in stoichiometric proportions defined in claim 1, and putting them into a ball mill tank for ball milling and mixing with zirconium ball as medium, then taking out the mixed powder, drying and sieving with a 60-mesh screen, and reserving the mixed powder; S2: taking Dy(C2H3O2)3·4H2O raw powder in stoichiometric proportions defined in claim 1, dissolving it in a polar aqueous solution to obtain a mixed solution, and reserving the mixed solution; S3: mixing the mixed powder in S1 and the mixed solution in S2 in a mortar, wherein the mixed solution is added in an amount of 10-40 wt% of the mixed powder, and the mixed powder is fully wetted, then the mixed powder is put into a mill, and is pressed under a pressure of 200-500 MPa and heated to 200-400 ℃ for 30 min-2 h to obtain a preliminarily densified ZnO pressure-sensitive ceramic body; S4: putting the ZnO pressure-sensitive ceramic body in S3 into a muffle furnace, and sintering it at a sintering temperature of 700-1000 ℃ for 1-5 h to further densify the ZnO pressure-sensitive ceramic body to obtain a ZnO pressure-sensitive ceramic product.

3. The method of claim 2, wherein the method is characterized by: The mass ratio of the powder in S1, the zirconium ball and the ball milling liquid medium is 1:10:1.5, wherein the mass ratio of the zirconium ball with a diameter of 1 cm, a diameter of 0.5 cm and a diameter of 0.2 cm is 2:1:1, and the rotation speed of the high-energy ball mill is 380 r / min.

4. The method of claim 2, wherein the method is characterized by: The particle size of the ZnO raw powder in S1 is about 500 nm, and the particle sizes of the Bi2O3, Co3O4, MnO2, Cr2O3, SnO2 and CaO raw powders are about 100 nm, about 200 nm, 100-300 nm, about 200 nm, <250 nm and <160 nm, respectively.

5. The method of claim 2, wherein the method is characterized by: The relative density of the ZnO pressure-sensitive ceramic body in S3 is 88%-94%.

6. The method of claim 2, wherein the method of preparing the dysprosium acetate solution doped ZnO varistor ceramic is characterized by: The heating rate of the sintering in S4 is 0.5-2 ℃ / min.

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