能量脉冲下高能ZnO压敏电阻的老化现象

DEGRADATION PHENOMENA UNDER ENERGY PULSE IN HIGH-ENERGY ZnO VARISTOR

研究了用于水轮发电机灭磁与过电压保护的高能ZnO压敏电阻在贮能电感释放的能量脉冲作用下的老化现象。研究表明,能量脉冲后,压敏电阻的特征电压、非线性系数和预击穿区V-I特性都发生跌落,而且这种跌落随脉冲次数增加而增加;能量脉冲使压敏电阻发生非对称老化。能量脉冲可以分解直流电压和能量两个分量。高能ZnO压敏电阻在能量脉冲下老化的原因是发生在晶粒耗尽层中和富铋晶界层中的离子迁移使双Schottky势垒降低。

The degradation phenomena under the energy pulse in the higy-energy ZnO varistorsused for de-excitation and overvoltage protection of hydroelectric generator were investigat-ed. The energy pulse was obtained by releasing the energy stored in an inductor. After the en-ergy pulse the values of the characterized voltage and the nonlinear coefficient of the varistorbecame smaller, and the pre-breakdown V-I curve moved to a lower position. The abovevariations were asymmetrical and increased with the increase of the number of the energypulse. The energy pulse can be equivalent to the combination of the dc field component andthe energy component. The degradation might arise from the deformation of the doubleSchottky barriers due to the ion migration occuring in the grain depletion layer and in the Bi-rich grain-bounday layer.