Specific features of the crystal and local structures of compounds formed in the Dy2O3–HfO2 system

Abstract

The crystal and local structures of compounds formed in the Dy₂O₃–HfO₂ system (at molar ratios from 1: 3 to 3: 1) in the course of isothermal annealing of X-ray amorphous mixed hydroxides at temperatures up to 1600°C have been studied. At the molar ratio Dy₂O₃: HfO₂ from 1: 3 to 1: 1, crystallization leads to formation of single-phase defect fluorite solid solutions nDy₂O₃ ∙ mHfO₂ with clearly pronounced nonequivalence of parameters of local environment of Dy³⁺ and Hf⁴⁺ cations. It has been found that Dy₂H₂O₇ (Dy₂O₃: HfO₂ = 1: 2) samples have a tendency to pyrochlore-type ordering in both the cationic and anionic sublattices.