Effects of Eu₂O₃ doping on microstructural and electronic properties of ZnO-Bi₂O₃-based varistor ceramics prepared by high-energy ball milling

DONG Yu-juan(董玉娟)^{1, 2, 3, 4}, CUI Feng-dan(崔凤单)², JIAO Lei(焦雷)², XU Hong-xing(徐红星)², TANG Dong-mei(唐冬梅)², WU Jie-ting(吴婕婷)², YU Ren-hong(于仁红)^{2, 5}, XU Dong(徐东)^{2, 3, 4}

(1. Faculty of Science, Jiangsu University, Zhenjiang 212013, China;
2. School of Material Science and Engineering, Jiangsu University, Zhenjiang 212013, China;
3. State key Laboratory of Electronic Thin Films and Integrated Devices (University of
Electronic Science and Technology of China), Chengdu 610054, China;
4. Changzhou Engineering Research Institute of Jiangsu University, Changzhou 213000, China
5. Changzhou Ming Errui Ceramics Co., Ltd., Changzhou 213102, China)

Abstract:ZnO-Bi₂O₃-based varistor ceramics doped with Eu₂O₃ in a range from 0 to 0.4% were obtained by high-energy ball milling and fired at 900-1 000 °C for 2 h. XRD and SEM were applied to determine the phases and microstructure of the varistor ceramics. A DC parameter instrument was applied to investigate the electronic properties and V–I characteristics. The XRD analysis of Eu₂O₃-doped ZnO-Bi₂O₃-based varistor ceramics shows that the ZnO, Eu-containing Bi-rich, Zn₇Sb₂O₁₂-type spinel and Zn₂Bi₃Sb₃O₁₄-type which is the pyrochlore phase are present. With increasing Eu₂O₃ content, the average size of ZnO grain firstly decreases and then increases. The grain boundary defect model was particularly used to explain the excellent nonlinearity of ZnO-Bi₂O₃-based varistor ceramics with the addition of 0.1 % Eu₂O₃ and sintered at 950 °C.

Key words:ceramics; varistors; rare earth; microstructure; electronic properties