Effects of alumina surrounding in sintering process on ZnO-Bi 2O3varistors doped with CoO

• Main Authors: Onreabroy W., Tunkasiri T., Sirikulrat N.
• Format: Article
• Language: English
• Published: 2014
• Online Access: http://www.scopus.com/inward/record.url?eid=2-s2.0-9644272421&partnerID=40&md5=b0ae1fec6091c7b9e4e6099c298e91e1; http://cmuir.cmu.ac.th/handle/6653943832/5011
• Institution: Chiang Mai University

Nonlinear current-voltage properties of zinc oxide-bismuth oxide varistors doped with cobalt oxide were investigated. The composition of ZnO doped with 0.5 mol% Bi2O3 and 0.75 mol%CoO was prepared and sintered in two different surroundings, zinc oxide-bismuth oxide-cobalt oxide powder and alumina powder. Microstructures and element tracing were studied using scanning electron microscopy with X-ray microanalysis, electron probe microanalysis and X-ray diffraction. Results clearly showed that the alumina surrounding led to bismuth loss from the green body and degraded the nonlinear property of varistors. At sintering temperatures higher than 1150°C, the alumina-surrounding sintered specimens became ohmic and the electrical resistivity of 200 Ω cm was found in the specimen sintered at 1200°C. © 2004 Elsevier B.V. All rights reserved.