Compositionally controlled rhombohedral to cubic phase transition in CsTe2−xWxO6 related to pyrochlore structure

CsTe2O6 adopts a rhombohedrally distorted pyrochlore related structure due to the 1:3 ordering of Te4+ and Te6+ in the octahedral sites respectively. Phases of the type CsTe2−xWxO6 were found to have the cubic pyrochlore structure from x = 0.2 to 0.5. These phases all contain Te4+ and Te6+ (mixed with W6+) and are disordered in octahedral sites of the pyrochlore structure. This mixed valence situation results in strong optical absorption in the visible region of the spectrum but does not produce a measurable electrical conductivity.