Variable-temperature single-crystal X-ray diffraction study of tetragonal and cubic perovskite-type barium titanate phases

• Published in: Acta crystallographica Section B, Structural science, crystal engineering and materials Vol. 72; no. Pt 1; p. 151
• Main Authors: Nakatani, Tomotaka, Yoshiasa, Akira, Nakatsuka, Akihiko, Hiratoko, Tatsuya, Mashimo, Tsutomu, Okube, Maki, Sasaki, Satoshi
• Format: Journal Article
• Language: English
• Published: England 01.02.2016
• Subjects: Barium - chemistry; Calcium Compounds - chemistry; Cations - chemistry; Crystallography, X-Ray; Molecular Structure; Oxides - chemistry; Titanium - chemistry; X-Ray Diffraction; X-ray diffraction; perovskite; BaTiO3; high temperature; ferroelectricity
• ISSN: 2052-5206
• DOI: 10.1107/S2052520615022544

A variable-temperature single-crystal X-ray diffraction study of a synthetic BaTiO3 perovskite has been performed over the temperature range 298-778 K. A transition from a tetragonal (P4mm) to a cubic (Pm3m) phase has been revealed near 413 K. In the non-centrosymmetric P4mm symmetry group, both Ti and O atoms are displaced along the c-axis in opposite directions with regard to the Ba position fixed at the origin, so that Ti(4+) and Ba(2+) cations occupy off-center positions in the TiO6 and BaO12 polyhedra, respectively. Smooth temperature-dependent changes of the atomic coordinates become discontinuous with the phase transition. Our observations imply that the cations remain off-center even in the high-temperature cubic phase. The temperature dependence of the mean-square displacements of Ti in the cubic phase includes a significant static component which means that Ti atoms are statistically distributed in the off-center positions.