不同类型冲击电流对ZnO压敏电阻老化的影响研究

Research on Influence of Different Types of Impulse Current on the Aging of ZnO Varistor

为了比较不同类型冲击电流对氧化锌(ZnO)压敏电阻直流老化的影响,将相同类型的ZnO压敏电阻样品分别开展2 ms方波(峰值为2 kA)耐受试验和4/10μs冲击电流(峰值为100 kA)试验。实验结果表明,在1~3轮(3~9次)的冲击耐受下,2 ms方波对ZnO压敏电阻的老化特性能起到一定优化作用,而4/10μs大电流冲击则使得ZnO压敏电阻老化特性持续劣化。利用扫描电子显微镜(SEM)、光谱仪、数字源表研究其微观结构以及电气性能参数变化。结合实验结果分析原因,4/10μs冲击电流对ZnO压敏电阻的损伤程度大于2 ms方波冲击电流的损伤程度,更容易引起ZnO压敏电阻的老化,在1~3轮(3~9次)2 ms方波耐受下,可以改善压敏电阻老化特性,其原因在于冲击电流产生热效应使构成晶界势垒亚稳定成分填隙锌离子在晶界发生反应而降低其浓度,得到比冲击前更稳定的晶界结,从而提高了其老化特性。

For comparing the influence of different types of impulse currents on DC aging of Zinc oxide(ZnO)varis⁃tors,the same type of Zinc oxide varistor samples are used to carry out 2 ms square wave(peak at 2 kA)withstand test and 4/10μs impulse current(The peak value is 100 kA)test.The experimental results show that under the impulse withstand of 1⁃3 rounds(3⁃9 times),the 2 ms square wave has a definite optimization on the aging characteristics of the ZnO varistor.While,the high current impulse at 4/10μs keeps the ZnO varistor’s aging characteristics continue to deteriorate.The scanning electron microscope(SEM),spectrometer,digital source meter are used to study its mi⁃crostructure and electrical performance parameter changes.The reason is analyzed in combination with the experi⁃mental results,the damage degree of the 4/10μs impulse current to the ZnO varistor is greater than that of the 2 ms square wave impulse current,which is more likely to cause the aging of ZnO varistor.Under the 2 ms square wave withstand for 1⁃3 rounds(3⁃9 times),the aging characteristics of varistors can be improved.The reason is that the ther⁃mal effect due to impulse current makes the interstitiated Zinc ion,which is a metastable component of the grain boundary barrier,react in the grain boundary and reduce its concentration,and obtain a more stable grain boundary junction than before the impact,thus improving its aging characteristics.