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Varistor ceramic preparation method reducing ZnO grain resistivity

A technology of grain resistivity and varistor, which is applied in the field of preparation of varistor ceramics with reduced ZnO grain resistivity, can solve problems such as the non-linear coefficient drops below 30, cannot meet industrial applications, and the leakage current density increases. , to achieve the effect of suppressing the decline of nonlinear coefficient, suitable for industrial applications, and suppressing the increase of leakage current

Inactive Publication Date: 2016-08-17
TSINGHUA UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

When the addition of Al ions reaches 0.05mol%, the leakage current density will increase to more than 20μA / cm2, and the nonlinear coefficient will drop below 30, which cannot meet the needs of industrial applications.

Method used

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Examples

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Effect test

preparation example Construction

[0026] A method for preparing varistor ceramics that reduces the resistivity of ZnO grains, the preparation raw materials include zinc oxide ZnO, bismuth oxide Bi 2 o 3 , antimony trioxide Sb 2 o 3 , manganese dioxide MnO 2 , chromium oxide Cr 2 o 3 , cobalt trioxide Co 2 o 3 , SiO2 2 , indium nitrate crystal In(NO 3 ) 3 9H 2 O, the preparation steps include a rough seed crystal step, a primary sintering step, a seed crystal refining step, a raw material mixing step, and a secondary sintering step.

[0027] In the step of preparing the seed crystal, the raw material for the preparation of the seed crystal and the mass fraction ratio of the preparation thereof are ZnO: Bi 2 o 3 : In(NO 3 ) 3 =20-50: 0.01-0.18: 0.1-0.4, the seed crystal roughing step method is:

[0028] The above-mentioned raw materials for preparing seed crystals were added to deionized water and alcohol, and ball milled for 8-12 hours to form a seed crystal suspension.

[0029] The seed crystal...

Embodiment 1

[0048] The raw material formula of the present embodiment is as follows:

[0049]The low residual voltage ZnO varistor ceramic raw material is prepared according to the following ratio: ZnO (94.8mol%), Bi 2 o 3 (0.7mol%), MnO 2 (0.5mol%), Sb 2 o 3 (1mol%), Co 2 o 3 (1mol%), SiO 2 (1.25mol%), In(NO 3 ) 3 9H 2 O (0.25mol%) and Cr 2 o 3 (0.5mol%);

[0050] The method of the present embodiment comprises the following steps:

[0051] Preparation of the seed crystal and the first step of sintering:

[0052] Using 25% ZnO and all In(NO 3 ) 3 9H 2 0; be placed in the ball mill tank that adds deionized water for 10 hours, and then dry as the seed crystal raw material;

[0053] Put the dried seed crystal raw material into a high-temperature electric furnace, and pre-fire it at 1300°C for 4 hours in the first step to form a hard block of seed crystal, and cool it to room temperature with the furnace;

[0054] After crushing the sintered hard block of seed crystals, put ...

Embodiment 2

[0066] The raw material formula of the present embodiment is as follows:

[0067] The low residual voltage ZnO varistor ceramic raw material is prepared according to the following ratio: ZnO (92.7mol%), Bi 2 o 3 (0.9mol%), MnO 2 (0.7mol%), Sb 2 o 3 (1.5mol%), Co 2 o 3 (1.5mol%), SiO 2 (1.7mol%), In(NO 3 ) 3 9H 2 O (0.4mol%) and Cr 2 o 3 (0.7mol%); The method of the present embodiment comprises the following steps:

[0068] Preparation of the seed crystal and the first step of sintering:

[0069] Using 25% ZnO and 25% Bi in the raw material formula 2 o 3 and all In(NO 3 ) 3 9H 2 0; be placed in the ball mill tank that adds deionized water for 12 hours, and then dry as the seed crystal raw material;

[0070] Put the ball-milled and dried seed crystal raw materials into a high-temperature electric furnace, pre-fire the first step at 1300°C for 6 hours to form a hard block of seed crystals, and cool to room temperature with the furnace;

[0071] After crushing t...

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Abstract

The invention discloses a varistor ceramic preparation method reducing ZnO grain resistivity. The preparation raw materials include zinc oxide ZnO, bismuth oxide Bi2O3, antimonous oxide Sb2O3, manganese dioxide MnO2, chromium oxide Cr2O3, cobalt oxide Co2O3, silicon dioxide SiO2 and indium nitrate crystal In(NO3)3.9H2O; and the preparation steps include a step of seed crystal roughing, a step of primary sintering, a step of seed crystal refinement, a step of raw material mixing and a step of secondary sintering. The method has the following beneficial effects: by strictly changing the control technology flow and the control technology parameters, the structural components and structural change of the material in the preparation process can be manually controlled, the grain resistivity and the residual voltage of ZnO varistor are reduced while the increase of leakage current and the decrease of nonlinear coefficient are inhibited, and thus the material has higher performance and is more suitable for industrial application.

Description

technical field [0001] The invention relates to the field of material preparation, in particular to a method for preparing varistor ceramics for reducing the resistivity of ZnO grains. Background technique [0002] ZnO varistors are made of ZnO as the main raw material, adding a small amount of Bi2O3, MnO2, Sb2O3, Co2O3, SiO2 and Cr2O3, etc., and are prepared by ceramic sintering process. Due to its good nonlinear performance and the advantages of large current capacity, since it was discovered in the 1870s, ZnO varistors have been widely used in power system lightning protection and power equipment protection as the core component of power system lightning arresters. As we all know, the insulation cost accounts for the main part of the power engineering cost. With the increase of the voltage level of the power system, the insulation consumption at the high voltage level is even greater. The insulation level of the power system is based on the residual voltage protection le...

Claims

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Application Information

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IPC IPC(8): C04B35/453C04B35/64
CPCC04B35/453C04B35/64C04B2235/3241C04B2235/3267C04B2235/3275C04B2235/3294C04B2235/3298C04B2235/3418C04B2235/656
Inventor 胡军何金良孟鹏飞
Owner TSINGHUA UNIV
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