Formation, Transformation, and Decomposition of Y2TeO6

A metastable modification of Y₂TeO₆ crystallizes at 770°C to 870°C at a heating rate of 10°C·min⁻¹ in air from an amorphous material prepared by the simultaneous hydrolysis of yttrium and tellurium alkoxides. It has a tetragonal unit cell with a=1.0428 nm and c=1.7524 nm. The tetragonal-to-hexagonal phase transformation occurs at 920° to 960°C. Hexagonal Y₂TeO₆ decomposes into Y₆TeO₁₂ and TeO₃↑ at 1220° to 1320°C; only Y₆TeO₁₂ is obtained as the decomposition product. Both modifications of Y₂TeO₆ are built up by octahedral TeO₆ groups.