Discovery of new phase and analysis of phase relationships in BaBiO3 with thermal analyses

Structural phase transition of BaBiO3 was investigated by using thermal analyses such as dilatometry, differential scanning calorimetry (DSC) and quantitative differential thermal analysis (DTA). First order phase transition, corresponding to so far reported structural one from monoclinic- to rhombohedral-distorted perovskite, was detected at 160 °C both in thermal expansion and DSC for the first time. Two kinds of phase transitions were also detected for the first time at 520 and 620 °C with dilatometry and quantitative DTA, respectively. High-temperature X-ray diffraction measurement revealed that crystal structure more than 620 °C was face centered cubic perovskite with ordered arrangement of Bi3+ and Bi5+. In 520–620 °C, X-ray diffraction peaks which indicated existence of superstructure were observed, which had been already proposed by electron diffraction measurement.