CHENG Lihong 1, SLAVKO Bernik 2, MATEJKA Podlogar 2, ZHENG Liaoying 3, LI Guorong 3
(1. Jiangxi Key Laboratory of Surface Engineering, Jiangxi Science & Technology Normal University, Nanchang 330038, Jiangxi
China;2.JoŽef Stefan Institute, Slovenia; 3.Shanghai Institute of ceramics, Chinese Academy of Sciences, Shanghai 200050, Jiangxi, China)
Abstract: By traditional ceramic processing method, ZnO-based varistor ceramics with the same amount of Bi2O3 and Sb2O3/Bi2O3=0.25,0.50 mared as LC1 and LC2 respectively were prepared. They were sintered by a traditional one stage or two-stage regimes in the temperature range of 800 ℃-950 ℃. Microstructural analysis results confirmed that the presence of rich-Bi2O3-based liquid phase was good for sintering,and could also promote the grain growth with the inversion boundaries (IB) inside the ZnO grains formed by Sb2O3. The samples had a proper density, homogeneous distribution of Bi2O3-rich secondary phase and grain size. The samples possessed good properties with breakdown voltages Eb in the range of 327 V/mm-670 V/mm, nonlinear coefficient α 20 to 31, and leakage current IL lower than 0.5 μA. LC2 have a smaller average grain size, higher Eb and α, and a lower IL than LC1. Results also confirmed that the temperature of the main sintering stage played the main role in influencing the average grain size. Conclusions were given that a suitable composition enables the proper microstructure development and good current-voltage characteristics of the varistors in the temperature range of 800 ℃-950 ℃.
Key words: ZnO; varistor; microstructure; electrical properties