Crystal structure of the high-temperature paraelectric phase in barium titanate BaTi_2O_5

摘要

Crystal structure of a ferroelectric barium titanate BaTi_2O_5 was investigated by the Rietveld analysis of neutron powder diffraction data measured at 706℃. The crystal structure of BaTi_2O_5 at 706℃ was refined assuming the centrosymmetric monoclinic A2/m space group. The crystal structures of the high-temperature A2/m and low-temperature A2 phases are similar. The displacement of atoms along the b axis is accompanied by the paraelectric A2/m to ferroelectric A2 phase transformation. The A2/m-A2 transition is not reconstructive but displacive.