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Neutron Powder Diffraction Study of a Phase Transition in La 0.68 (Ti 0.95 Al 0.05 )O 3
Author(s) -
Ali Roushown,
Izumi Fujio,
Yashima Masatomo
Publication year - 2006
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.1551-2916.2006.01324.x
Subject(s) - orthorhombic crystal system , tetragonal crystal system , neutron diffraction , crystallography , materials science , rietveld refinement , perovskite (structure) , powder diffraction , phase transition , crystal structure , phase (matter) , octahedron , analytical chemistry (journal) , atmospheric temperature range , chemistry , condensed matter physics , physics , organic chemistry , chromatography , meteorology
Crystal structures and structural changes of the compound La 0.68 (Ti 0.95 Al 0.05 )O 3 have been studied using neutron powder diffraction data and the Rietveld method in the temperature range from 25° to 592°C. The Rietveld profile‐fitting analyses of the neutron data and the synchrotron diffraction profile revealed that the crystal symmetry of the low‐temperature phase of La 0.68 (Ti 0.95 Al 0.05 )O 3 is orthorhombic Cmmm (2 a p × 2 a p × 2 a p ; p: pseudo‐cubic perovskite). The unit‐cell and structural parameters were successfully refined with the orthorhombic Cmmm for the intensity data measured at 25°, 182°, and 286°C, and with the tetragonal P 4/ mmm ( a p × a p × 2 a p ) for intensity data obtained at 388° and 592°C. The P 4/ mmm ‐to‐ Cmmm phase transition was found to be induced by tilting of the (TiAl)O 6 octahedron. The tilt angle decreased with increasing temperature, reaching 0° at the Cmmm – P 4/ mmm transition temperature.