Crystal structure and phase transitions of image

The crystal structure of image, prepared by solid state reaction, was determined by high-resolution X-ray diffraction at different temperatures. At room temperature, this compound has a monoclinic structure (space group image) with image, image, image, image. At 1105 K the structure is converted to tetragonal (space group image). Diffraction data also suggest that a cubic phase exists above 1220 K. Comparing the phase transition temperatures of image with those of other compounds of the image family reported previously, it was observed that the transition temperatures are higher in compounds with low-tolerance factors. At the same time, the temperature range in which the intermediate tetragonal phase exists is reduced.