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Effects of Microstructure and Composition on the Curie Temperature of Lead Barium Niobate Solid Solutions
Author(s) -
Hiroshima Takuya,
Tanaka Kazuhiko,
Kimura Toshio
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.tb08100.x
Subject(s) - curie temperature , materials science , ferroelectricity , microstructure , tetragonal crystal system , curie , condensed matter physics , dielectric , curie constant , phase (matter) , barium titanate , mineralogy , curie–weiss law , composite material , crystal structure , crystallography , ferromagnetism , chemistry , physics , optoelectronics , organic chemistry
The Curie temperature of normally sintered and hot‐pressed Pb 1‐x Ba x Nb 2 O 6 ( x = 0.30, 0.37, 0.41, and 0.50) was dependent on the sample preparation conditions. Samples with large amounts of pores and cracks had higher Curie temperatures than dense samples. Dense samples with fine grains had higher Curie temperatures than those with coarse grains. Comparison between microstructure and the Curie temperature revealed that the variation in Curie temperature was caused by internal stresses developed in the paraelectric‐to‐ferroelectric phase transition. Large internal stresses increased the free energy of the ferroelectric phase, and thus decreased the Curie temperature. The magnitude of internal stresses depended on the microstructure. Pores and cracks relaxed internal stresses, resulting in high Curie temperatures. Grain boundaries also relaxed internal stresses; samples with small grains had high Curie temperatures. Furthermore, the magnitude of internal stresses was dependent on the crystal structure of ferroelectric phases; samples with the tetragonal ferroelectric structure had internal stresses larger than those with the orthorhombic ferroelectric structure. The effect of crystal structure was discussed in terms of the relaxation of internal stresses by the formation of 90° domains