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Thermal Expansion and High‐Temperature Phase Transition of Ba 6−3 x Ln 8+2 x Ti 18 O 54 (Ln=La, Nd, and Sm) Ceramics
Author(s) -
Qin Ni,
Liu Xiao Qiang,
Chen Xiang Ming
Publication year - 2007
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.1551-2916.2007.01684.x
Subject(s) - thermal expansion , analytical chemistry (journal) , materials science , phase transition , atmospheric temperature range , ceramic , transition temperature , diffraction , phase (matter) , solid solution , x ray crystallography , mineralogy , chemistry , thermodynamics , condensed matter physics , metallurgy , superconductivity , physics , optics , organic chemistry , chromatography
Thermal expansion behaviors of Ba 6−3 x Ln 8+2 x Ti 18 O 54 (Ln=La, Nd, and Sm, x =0.5, 0.67, and 0.75) ceramics were determined by dilatometric measurement. The samples of all investigated compositions expanded nearly linearly with increasing temperature in the range of 20°–1200°C. Their thermal expansion coefficients were determined to be 10.7–11.4 ppm/°C. A discontinuous change in sample size was observed at about 1350°C for each composition, indicating the existence of a phase transition. As determined by the high‐resolution X‐ray diffraction analysis, the phase constitution and the lattice parameters of Ba 6−3 x Sm 8+2 x Ti 18 O 54 ceramics were maintained in the quenched samples. The origin of the phase transition was discussed thoroughly. Phase equilibrium in the BaTiO 3 –Ln 2/3 TiO 3 system was reviewed by considering the phase transition.