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Sintering of Zinc Oxide Doped with Antimony Oxide and Bismuth Oxide
Author(s) -
Kim Jinho,
Kimura Toshio,
Yamaguchi Takashi
Publication year - 1989
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/j.1151-2916.1989.tb07659.x
Subject(s) - pyrochlore , materials science , sintering , microstructure , eutectic system , bismuth , phase (matter) , oxide , doping , chemical engineering , antimony oxide , metallurgy , mineralogy , chemistry , optoelectronics , organic chemistry , engineering
The phase change, densification, and microstructure development of ZnO doped with both Bi 2 O 3 and Sb 2 O 3 are studied to better understand the sintering behavior of ZnO varistors. The densification behavior is related to the formation of pyrochlore and liquid phases; the densification is retarded by the former and promoted by the latter. The pyrochlore phase, whose composition is Bi 3/2 ZnSb 3/2 O 7 , appears below 700°C. The formation temperature of the liquid phase depends on the Sb/Bi ratio: about 750°C for Sb/Bi < 1 by the eutectic melting in the system ZnO—Bi 2 O 3 , and about 1000°C for Sb/Bi > 1 by the reaction of the pyrochlore phase with ZnO. Hence, the densification rate is determined virtually by the Sb/Bi ratio and not by the total amount of additives. The microstructure depends on the sintering temperature. Sintering at 1000°C forms intragrain pyrochlore particles in ZnO grains as well as intergranular layers, but the intragrain particles disappear at 1200°C by the increased amount of liquid phase, which enhances the mobility of the solid second phase.