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Massive Transformation in Gd2O3‐Bi2O3 Ceramics
Author(s) -
Su Pomin,
Virkar Anil Y
Publication year - 1996
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.1151-2916.1996.tb08131.x
Subject(s) - materials science , crystallite , trigonal crystal system , kinetics , phase (matter) , ceramic , sintering , electrical resistivity and conductivity , enthalpy , thermodynamics , transformation (genetics) , activation energy , crystallography , mineralogy , analytical chemistry (journal) , crystal structure , composite material , metallurgy , chemistry , physics , biochemistry , organic chemistry , chromatography , quantum mechanics , gene
Gd 2 O 3 ‐doped Bi 2 O 3 polycrystalline ceramic samples containing between 10 and 26 mol% Gd 2 O 3 were fabricated by pressureless sintering of powder compacts. As‐sintered samples were cubic (CaF 2 structure). The cubic solid solutions underwent transformation to a rhombohedral phase when annealed at lower temperatures. Under certain conditions, the cubic phase fully transformed to the rhombohedral phase of the same composition, and the kinetics were thermally activated. This suggested that the cubic → rhombohedral transformation was a massive transformation. The transition temperatures for the occurrence of a massive transformation were experimentally determined by measuring the conductivity as a function of temperature, as well as by measuring growth rate of the rhombohedral precipitates as a function of temperature. The activation enthalpy for interface motion was measured to be ∼200 kJ/mol for the samples studied. The kinetics of cubic → rhombohedral transformation could be described by the Johnson‐Mehl‐Avrami equation.