Thermal stability of Bi2O3

Differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of an alpha-Bi2O3 sample revealed staged phase transitions in the range 720-800 degrees C ( at 720, 780, and 800 degrees C) and the elimination of oxygen to the composition Bi2O2.967 during heating to 895 degrees C in air at 16 K/min. In dynamic vacuum ( p = 1.33 Pa) at 780-800 degrees C, Bi2O3 consecutively transforms to a phase with the cubic gamma-Bi2O3 structure and tetragonal Bi2O2.3-2.4. In the latter, electron diffraction in a transmission electron microscope (ED/TEM) shows a superstructure with the superstructure vector q(110)approximate to 1/9, which indicates an ordered arrangement of oxygen vacancies.