镨系氧化锌非线性电阻微观结构及性能

Microstructure and Properties of ZnO-Pr_6O_(11)-based Nonlinear Varistor

采用X-射线衍射,扫描电子显微镜和X-射线能谱等方法,分析了镨系和铋系非线性电阻的微观结构;测试了不同烧成温度下镨系氧化锌非线性电阻片的电位梯度、残压比、泄漏电流和体密度。结果表明,镨系氧化锌非线性电阻在组成方面避免了铋系的一些固有缺陷,高温下成分相对稳定;镨系的微观结构只包括ZnO和以氧化镨为主的晶界层,与铋系相比,它增加了晶粒边界层的有效面积。以上两种因素使镨系易于实现较高电位梯度和较大通流容量。烧成温度对镨系及铋系性能的影响比较相似。在配方和工艺设计方面,如何对氧化锌晶粒生长进行有效制约,增加单位厚度晶粒数目,是实现高电位梯度的关键,而综合性能的提高,有赖于在烧成温度范围内对温控点进行有效控制。

The microstructure of ZnO-Pr_6O_(11)-based varistors and ZnO-Bi_2O_3-based varistors were analysized by using X-ray diffraction (XRD),scanning electron microscope(SEM),energy-disperse X-ray spectroscope(EDX) etc technical ways.Voltage gradient,residual voltage ratio,leakage current and volume density of ZnO-Pr_6O_(11)-based varistors sintered at different temperature were tested,The results show that ZnO-Pr_6O_(11)-based varistors eliminate some innate defects of ZnO-Bi_2O_3-based varistor,keeping relatively stable at high temperature;the texture of ZnO-Pr_6O_(11)-based varistor contains mere ZnO and boundary layer mainly consisting praseody-miun oxide,which lead to the increasement of effective area of boundry layer,these two factors make ZnO-Pr_6O_(11)based varistor easily obtain higher voltage gradient and better energy absorption capability.As for the effect of the sintering temperature,the situation of ZnO-Pr_6O_(11)-based varistor is similiar to that of ZnO-Bi_2O_3-based varistor.As far as recipe and technological designing is concerned,it is important to successfully inhibit ZnO grain growing and to increase the amount of grain boundary layers for enhancement of the voltage gradient,In addition,better comprehensive properties depends upon the temperature-controlling within the scope of sintering temperature.