Abstract
New phases have been discovered in high functional perovskite-type oxides with various thermal analyses and X-ray diffraction under specific conditions such as high temperatures and high pressures. The second order phase transition was observed in Ba2In2O5 at 1070°C by dilatometry and quantitative DTA. It was revealed that distortion from the ideal cubic perovskite structure is the smallest in the phase found at higher temperatures than 1070°C and that this phase has the highest potential as an oxide-ion conductor among three phases in Ba2In2O5. In addition to the three phases in BaBiO3 already discovered by neutron diffraction measurement so far, another phase has been observed by dilatometry and quantitative DTA in temperature range 520∼620°C. The X-ray diffraction peaks indicating existence of superstructure was observed in diffraction pattern of BaBiO3 at 600°C. Variations of enthalpy, ΔH, and volume, ΔV, were estimated by DSC and high-temperature X-ray diffraction, respectively. Combining Clapeyron formula, positive ΔH and negative ΔV, phase transition under high pressure at room temperature was deduced and confirmed by X-ray diffraction at high pressures.
