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Investigation of the solidus boundaries and microstructure in the ZnO–PrO1.5–CoO system

Published online by Cambridge University Press:  31 January 2011

Sung-Yong Chun ,
Naoki Wakiya ,
Kazuo Shinozaki  and
Nobuyasu Mizutani
Sung-Yong Chun
Affiliation:
Department of Inorganic Materials, Faculty of Engineering, Tokyo Institute of Technology, 2-12-10-okayama, Meguro-ku, Tokyo 152, Japan
Naoki Wakiya
Affiliation:
Department of Inorganic Materials, Faculty of Engineering, Tokyo Institute of Technology, 2-12-10-okayama, Meguro-ku, Tokyo 152, Japan
Kazuo Shinozaki
Affiliation:
Department of Inorganic Materials, Faculty of Engineering, Tokyo Institute of Technology, 2-12-10-okayama, Meguro-ku, Tokyo 152, Japan
Nobuyasu Mizutani
Affiliation:
Department of Inorganic Materials, Faculty of Engineering, Tokyo Institute of Technology, 2-12-10-okayama, Meguro-ku, Tokyo 152, Japan
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Abstract

ZnO ceramics used as varistors are prepared with cobalt oxide as an essential additive to improve nonohmic properties. Because some of its effects during the liquid-phase sintering remain unexplained, we characterize the liquid-phase formation temperatures and phase reactions in the system ZnO–PrO1.5–CoO. Using differential thermal analysis (DTA) during sintering, we detect new thermal phenomena. An addition of cobalt oxide to ZnO–PrO1.5 mixtures (ZnO–5 mol% PrO1.5–10 mol% CoO) significantly decreases the liquid-phase formation temperature to 1272 ± 5 °C, which is about 110 °C lower compared to those in the ZnO–PrO1.5 system. Characterization of ceramics quenched during sintering allows us to describe an isoplethal section with PrO1.5 contents of 5 mol% and solubility limit of Co in ZnO.

Type
Articles
Information
Journal of Materials Research , Volume 13 , Issue 8 , August 1998 , pp. 2110 - 2116
Copyright
Copyright © Materials Research Society 1998

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