High-purity SiC voltage-sensitive 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: 2017-10-10
SHANGHAI INST OF CERAMIC CHEM & TECH CHINESE ACAD OF SCI
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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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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[0022] As a high-density and high-purity SiC pressure-sensitive ceramic and a preparation method thereof, the invention comprises the following steps: using high-purity SiC powder as a raw material. The raw materials are placed at the bottom of the graphite crucible of the medium frequency induction high temperature sintering furnace, and the porosity is 50%-70%. Vacuumize the furnace, heat the graphite crucible to a certain temperature of 1200°C, and remove the impurities adsorbed by the SiC powder at high temperature. Introduce high-purity Ar gas, and the air pressure is controlled within a certain range (the air pressure is 10 3 -10 5 Pa), the temperature of the furnace was raised to 2200°C, and the temperature gradient in the height direction of the crucible was controlled at 2.5°C-4.0°C / mm. The particle size of the SiC powder is 0.1-1 μm. The purity of the SiC powder is 99.9wt%. The vacuum degree≤10 -3 Pa.

[0023] The SiC ceramic density prepared by the present inv...

Embodiment 1

[0026] Select SiC high-purity 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°C, and remove the impurities adsorbed by SiC powder at high temperature; feed high-purity Ar gas, and control the air pressure at 10 3 Pa, raise the temperature of the furnace to 2200°C, the temperature gradient of the furnace height is controlled at 2.5°C / mm; the holding time is 30min, and SiC ceramics are obtained, and the density of the SiC ceramics is 3.21g / cm 3 , whose microstructure is as figure 2 shown, from figure 2 The grain size of SiC ceramics can be known in the figure. Process the obtained SiC ceramics into discs with a thickness of Φ10 mm and a thickness of 2 mm, and smooth both ends, and even...

Embodiment 2

[0028] Select SiC high-purity 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°C, and remove the impurities adsorbed by SiC powder at high temperature; feed high-purity Ar gas, and control the air pressure at 10 3 Pa, raise the temperature of the furnace to 2200°C, the temperature gradient of the furnace height is controlled at 3°C / mm; the holding time is 30min, and SiC ceramics are obtained, and the density of the SiC ceramics is 3.20g / cm 3 . Process the obtained SiC ceramics into a disc with a thickness of Φ10 mm and a thickness of 2 mm, and smooth both ends of it, and evenly coat silver paste electrodes on both ends, and then keep it in a muffle furnace for 30 minutes at 750 ° C to obt...

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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, belonging 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 piezoresistor. Varistors have a wide range of applications and can be used for spark extinguishing, overvoltage protection, preparation of lightning rods, and voltage stabilization. Since 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 telecommun...

Claims

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Application Information

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IPC IPC(8): C04B35/565C04B35/622H01C7/118
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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