PTCR ceramics produced from oxalate-derived barium titanate

BaTiO 3 powders with an average crystallite size from 68 to 2000 nm have been prepared by calcining barium titanyl oxalate at temperatures from 700 to 1150°C, and their morphology and recrystallization kinetics have been studied. The powders have been used to produce positive temperature coefficient...

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Bibliographic Details
Published in:Inorganic materials 2008-08, Vol.44 (8), p.905-910
Main Authors: Shut, V. N., Kostomarov, S. V., Gavrilov, A. V.
Format: Article
Language:English
Subjects:
Asymptotic properties
Barium titanates
Ceramics
Chemistry
Chemistry and Materials Science
Crystallites
Electric strength
Industrial Chemistry/Chemical Engineering
Inorganic Chemistry
Materials Science
Oxalates
Recrystallization
Roasting
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Summary:BaTiO 3 powders with an average crystallite size from 68 to 2000 nm have been prepared by calcining barium titanyl oxalate at temperatures from 700 to 1150°C, and their morphology and recrystallization kinetics have been studied. The powders have been used to produce positive temperature coefficient of resistance (Ba,Ca,Pb)TiO 3 ceramics, and the microstructure and electrical properties of the ceramics have been investigated. The results indicate that improving the crystallinity of the barium titanate powder suppresses recrystallization in the ceramics, increases their resistivity, and has a significant effect on their resistance jump and electric strength. We have identified the optimal temperature range of barium titanyl oxalate calcination, which insures the highest electric strength of PTC thermistors with a resistance of 31 Ω. The corresponding crystallite size of the barium titanate powder is ≃200 nm.
ISSN:0020-1685
1608-3172
DOI:10.1134/S0020168508080232