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Investigation on Doping Modification of SnO2 Varistors

Author: ZhouZiYang
Tutor: LuZhenYa
School: South China University of Technology
Course: Microelectronics and Solid State Electronics
Keywords: SnO2 varistors Doping Nonlinear coefficient Withstand pulse performance
CLC: TM54
Type: Master's thesis
Year: 2011
Downloads: 33
Quote: 1
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Abstract


Having a stable resistance of the non-linear characteristics and high pulse energy amount as the the lightning overvoltage core, varistor requirements. SnO 2 sensitive ceramic materials due to thermal conductivity (about 2 times the thermal conductivity of the ZnO-based varistors) high temperature and other advantages of to withstand pulsed current is too large and failure is not like the ZnO varistor element prone to explosion or perforation destruction, and therefore has a very important meaning, and good prospects for development. But for now, there is still a certain distance of of SnO 2 varistor electrical properties with ZnO varistor, and thus needs to be further improved. In this paper, on the basis of previous studies, through oxide doping and craft adjustment SnO 2 varistors doped modified to improve its a small current characteristics and tolerance pulse performance. The nonlinear characteristics of the varistor originated in the grain resistance and grain boundary resistance huge difference, so you want to get the high nonlinearity, the ceramic grains higher semiconductor degree. Thesis the niobium oxalate instead of Nb 2 O 5 as donor doping study SnO 2 electrical performance of the varistor material . The results showed that the introduction of niobium oxalate to promote ceramic semiconductive doping amount of 0.3wt% of the sample to obtain the best nonlinear (α is equal to 42) and the highest tolerance pulse current value (up to 2132A); doped Nb 2 O 5 samples compared to samples doped niobium oxalate with low residual voltage ratio, this is mainly porcelain inside and niobium oxalate distribution uniform. On the basis of previous work, we have adopted SiO 2 further improve SnO 2 sintering properties, Si 4 smaller radius, the lattice The the after easily cause lattice distortion, thereby promoting the ceramic sintered, but the deterioration of the nonlinear characteristic of the sample in a small current, while the excess of SiO 2 hinder grain growth and destruction of grain boundary is formed. The right amount of SiO 2 withstand pulse current value of the sample, can significantly improve the residual pressure ratio increases as the SiO 2 content increases. In view of the the doped SiO 2 sample small current poor non-linear characteristics, we were introduced to the basic magnesium carbonate ((MgCO 3 ) 4 < / sub> · Mg (OH) 2 · 5H 2 O) and SrCO 3 to improve the non-linear characteristics of the sample. The results showed that the introduction of an appropriate amount of basic magnesium carbonate is conducive to improve the uniformity of the grain size, thereby improving the characteristics of the small current of the sample, while improving the tolerance of the sample pulse performance, the doping amount of 0.3wt% of the sample is the highest resistance by pulse current value 3900A residual pressure ratio of 2.098. Samples doped with SrCO 3 , have better current characteristics, nonlinear coefficient α are more than 40, the leakage current is less than 2μA; Sr 2 radius easily segregates at the grain boundary to inhibit grain growth, ceramic pores increased, along with the the SrCO 3 increase of, V 1mA gradually increased, ε r decreased tolerance pulse current value decline, the residual voltage ratio to rise.

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CLC: > Industrial Technology > Electrotechnical > Electrical > Resistor,potentiometer
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