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A high-purity sic varistor ceramic

A technology of varistor ceramics and powders, which is applied in varistors, varistor cores, etc., can solve the problems of performance impact and difficulty in ensuring the stability of electrical performance, etc., and achieve the effect of good pressure stability

Active Publication Date: 2020-05-19
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0003] At present, SiC ceramics can obtain dense SiC ceramics mainly by adding sintering aids. The most common SiC ceramics are solid-phase sintered SiC ceramics with B-C system and liquid-phase sintered SiC ceramics with alumina and yttrium oxide. SiC ceramics with sintering aids have a certain impact on their performance due to the existence of grain boundary phases, and the stability of electrical properties is difficult to guarantee

Method used

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  • A high-purity sic varistor ceramic
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preparation example Construction

[0022] As a high-density and high-purity SiC pressure-sensitive ceramic and its preparation method, it includes the following steps: using high-purity SiC powder as a raw material. The raw materials are placed at the bottom of a graphite crucible in an intermediate frequency induction high-temperature sintering furnace, and the porosity is 50%-70%. The furnace is evacuated, the graphite crucible is heated to a certain temperature of 1200°C, and the impurities adsorbed by the SiC powder are removed at a high temperature. Inject high-purity Ar gas, the pressure is controlled within a certain range (the pressure is 10 3 -10 5 Pa), the furnace is heated to 2200°C, and the temperature gradient in the height direction of the crucible is controlled at 2.5°C-4.0°C / mm. The particle size of the SiC powder is 0.1 to 1 μm. The purity of the SiC powder is 99.9% by weight. The vacuum degree ≤ 10 -3 Pa.

[0023] The density of the SiC ceramic prepared by the invention is 3.21±0.01gcm -3 , Th...

Embodiment 1

[0026] Select high-purity SiC powder with an average particle size of 0.5 microns and a purity of 99.9%. Put the SiC powder into the bottom of the graphite crucible of an intermediate frequency induction graphite furnace. The porosity of the powder is 0.6; the furnace is evacuated and the vacuum degree is controlled at 10 -3 Below Pa, heat the graphite crucible to 1200℃, remove the impurities adsorbed by the SiC powder at high temperature; pass in high-purity Ar gas, and control the pressure at 10 3 Pa, the furnace is heated to 2200°C, and the temperature gradient of the furnace height is controlled at 2.5°C / mm; the holding time is 30min to obtain SiC ceramics, the density of the SiC ceramics is 3.21g / cm 3 , Its microstructure such as figure 2 Shown from figure 2 It can be seen the grain size of SiC ceramics. The obtained SiC ceramics were processed into wafers with a thickness of Φ10mm and a thickness of 2mm, and the two ends were ground flat, and silver paste electrodes were ...

Embodiment 2

[0028] Select high-purity SiC powder with an average particle size of 0.5 microns and a purity of 99.9%. Put the SiC powder into the bottom of the graphite crucible of an intermediate frequency induction graphite furnace. The porosity of the powder is 0.6; the furnace is evacuated and the vacuum degree is controlled at 10 -3 Below Pa, heat the graphite crucible to 1200℃, remove the impurities adsorbed by the SiC powder at high temperature; pass in high-purity Ar gas, and control the pressure at 10 3 Pa, the furnace is heated to 2200°C, and the temperature gradient of the furnace height is controlled at 3°C / mm; the holding time is 30min to obtain SiC ceramics, the density of the SiC ceramics is 3.20g / cm 3 . The obtained SiC ceramics were processed into wafers with a thickness of Φ10mm and a thickness of 2mm, and the two ends were ground flat, and silver paste electrodes were evenly coated on both ends, and then they were kept in a muffle furnace at 750°C for 30 minutes. The SiC c...

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Abstract

The invention relates to a high-purity SiC voltage-sensitive ceramic. The density of the SiC voltage-sensitive ceramic is 3.21+ / -0.01gcm<-3> and the volt-ampere characteristics are kept unchanged at 20-100 DEG C. A preparation method for the SiC voltage-sensitive ceramic comprises the following steps: placing SiC powder into the bottom of a graphite crucible and controlling the powder porosity within 50-70%; increasing the temperature to 1200-1400 DEG C in vacuum, thereby eliminating the impurities absorbed by the SiC powder; introducing inert atmosphere and continuously increasing temperature to 2100-2300 DEG C, controlling the pressure within 103-105Pa, controlling the temperature gradient along the height direction of the graphite crucible within 2.5-4 DEG C / cm, keeping the temperature for 30-120 minutes and adopting a physical gas phase transmission method for growing the SiC voltage-sensitive ceramic on an inner surface of a top cover of the graphite crucible.

Description

Technical field [0001] The invention relates to a high-density and high-purity SiC ceramic pressure-sensitive ceramic and a preparation method thereof, and belongs to the field of SiC ceramics. Background technique [0002] Varistor ceramic material refers to a semiconductor ceramic material that has nonlinear volt-ampere characteristics at a certain temperature and within a certain voltage range, and its resistance decreases sharply with the increase of voltage. According to this nonlinear volt-ampere characteristic, this semiconductor ceramic material can be used to make a nonlinear resistor, that is, a varistor. Varistors have a wide range of applications, such as spark extinguishing, overvoltage protection, preparation of lightning rods, and voltage stabilization. Because varistors play an important role in protecting equipment safety and ensuring normal and stable operation of equipment, they have been widely used in aviation, aerospace, post and telecommunications, railway...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H01C7/118C04B35/565C04B35/622
CPCC04B35/565C04B35/622C04B2235/658C04B2235/77C04B2235/96H01C7/118
Inventor 陈健黄政仁朱云洲刘学建陈忠明姚秀敏刘岩袁明
Owner SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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