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Nature of Cation Vacancies Formed to Compensate Donors during Oxidation of Barium Titanate
Author(s) -
Yamada Atsushi,
Chiang YetMing
Publication year - 1995
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.1151-2916.1995.tb08413.x
Subject(s) - barium titanate , vacancy defect , barium , materials science , grain boundary , auger electron spectroscopy , diffusion , titanium , inorganic chemistry , mineralogy , chemical engineering , analytical chemistry (journal) , crystallography , chemistry , metallurgy , ceramic , microstructure , thermodynamics , physics , chromatography , nuclear physics , engineering
Oxidative cooling is a critical step in the processing of barrier layer electroceramics based on BaTiO 3 . While it has been proposed that barium vacancies are formed at the grain boundaries to compensate donors, 1, 2 no direct evidence for this mechanism exists. On the other hand, literature data can be found to support the compensation of donors in the bulk by either barium or titanium vacancies. As a result the defect(s) formed at electrically active titanate grain boundaries during oxidation has remained uncertain. We explore this phenomenon by observing changes in the surface composition of donor‐doped BaTiO 3 when cation vacancies are introduced during oxidation, using SAES (scanning Auger electron spectroscopy). Direct experimental support for the formation and in‐diffusion of barium vacancies during oxidative cooling is obtained in a composition containing 0.7% Nb. It is suggested that barium vacancy compensation constitutes a metastable defect equilibrium in BaTiO 3 . In a sample of lower concentration (0.3% Nb), results are inconclusive, perhaps because of slower oxidation limited by surface reaction kinetics.