High-temperature degradation of the polar phase of bismuth telluriteстатья
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Дата последнего поиска статьи во внешних источниках: 18 июля 2013 г.
Местоположение издательства:Road Town, United Kingdom
Первая страница:1819
Последняя страница:1823
Аннотация:Powders and crystals formed in the Bi2O3-TeO2 system near the Bi2TeO5 composition were studied in the subsolidus region at 600-900 degrees C by thermal analysis, second optical harmonic generation, and conductometry techniques. The occurrence of the reversible polar phase-centrally symmetrical phase transition at 780-820 degrees C accompanied by a diffuse endothermic effect was substantiated by X-ray data. Taking into account the special features of the crystal structure of Bi2TeO5, the conclusion was drawn that redistribution of oxygen over vacant sites of the oxygen-deficient fluorite-like crystal lattice in this temperature region was responsible for intense dielectric relaxation and high conductivity. The structural mechanism of the transition was shown to be different from ferroelectric. An alternative physicochemical mechanism was suggested. This mechanism was based on the assumptions of, first, high anionic conductivity in the centrally symmetrical Bi2TeO5 phase disordered with respect to oxygen and, second, oxygen atom displacements by distances of the order of interatomic distances during the phase transition.