Phase transitions of polycrystal yttrium oxide during heating in vacuum

Phase transformations in polycrystal yttrium oxide heated in vacuum in the range of 25-1800 deg C were studied. It is pointed out that in the range of 500-1200 deg C yttrium oxide undergoes primary phase transition from ordered phase to disordered one of the C type. Thermal coefficients of linear expansion of the phases in the range of 25-1800 deg C in vacuum differ significantly. The difference in lattice periods of the ordered and disordered phases of the C type coincides with the difference in the values of anion ionic radii and anionic vacancy, being 0.0015 nm