国外MOA用ZnO电阻片的剖析与思考

对国外五家公司的ZnO电阻片进行了试验,并与已知ZnO电阻片样品配方对比,结果表明,五家样品的压比较低、老化系数呈下降型;其配方成分都含有Ni,D试样几乎不含Si、Cr,但是其方波通流密度较高;虽然与国内样品的显微结构相比,其物相组分相似,无明显的差别,但是多数瓷体中的大气孔较少,端面全喷铝或者留边宽度较窄。据此,提出了从根本上改进配方和工艺,如掺杂Ni,细化添加剂粒度、选择适宜的有机添加剂及添加量,以改善喷雾干燥粉料成分和成型坯体密度的均匀性;根据不同的配方,研究相适应的烧成制度,特别是冷却制度、热处理温度制度等多种思路,以期全面提高我国ZnO电阻片的性能水平。

Analysis and Consideration of Foreign ZnO Varistors for MOA

Verification was made on ZnO varistors of 5 foreign mannfatures and comparision was made with varistors known composition.The results show low voltage ratio and descend tendency of ageing factor and high discharge current density of these varistors,all having Ni ingredient,and practically not Si and Cr ingredients for sample D.The microstructures of these varistors show similar crystal phases with domestic ones.But a few number of great pores,with the aluminium coating on whole end surfaces or with a small gap at fringe.On this basis some consideration is proposed for improving characteristics of Chinese varistors,e.g.,improvement of composition and technology with Ni dosing,increase fineness of additives,introduction of appropriate organic additive and dose for improving evenness of dried powder and pressed body,and prescribing applicable firing schedules for different varistor compositions,especially cooling and thermal treatment schedule.