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January 27th, 2010

Formation and Stability of Ferroelectric BaTi2O5

Published on January 27th, 2010 | By: pwray@ceramics.org

Volume 93 Issue 1, Pages 295 – 300

 

Na Zhu, Anthony R. West
Published Online: Nov 23 2009 6:56PM

DOI: 10.1111/j.1551-2916.2009.03393.x

 

ABSTRACT
BaTi2O5
(BT2) is thermodynamically stable over a very
narrow temperature range between 1220° and 1230°C: a modification to the
BaO–TiO2 phase diagram is proposed. This
thermodynamic stability was shown by constructing a time–temperature
transformation diagram for the decomposition of BT2.
Once formed, BT2 appears to be stable
indefinitely at 1220°–1230°C; at higher temperatures, the decomposition
rate increases with temperature; at lower temperatures, the
decomposition rate increases with decreasing temperature and passes
through a maximum at ∼1200°C; below ∼1150°C, BT2
has long-lived kinetic stability. Kinetic considerations show a
nucleation and growth mechanism for decomposition, with a nucleation
induction period that is very temperature dependent. BT2
can be prepared by various routes, including solid-state reaction of
oxides below ∼1100°C; because it is metastable at all temperatures other
than 1220°–1230°C, its formation is an example of Ostwald’s rule of
successive reactions. Discrepancies in the literature concerning the
reported stability range of BT2 can be explained
by the complex dependence on temperature and time of both its formation
and decomposition, for both of which, the nucleation stage is rate
limiting.

 

Online Access to Journal of the American Ceramic Society


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