Crystal structure features of the mixed-valence tellurium β-pyrochlores: CsTe1.625W0.375O6 and RbTe1.5W0.5O6

Two new isostructural mixed-valence tellurium oxides, CsTe1.625W0.375O6 (1) and RbTe1.5W0.5O6 (2), have been synthesized by solid-state reaction. The single crystals of obtained compounds have been characterized by single-crystal X-ray diffraction analysis. Both compounds have β-pyrochlore-type structure (cubic system, space group Fd-3m, Z ​= ​8) and the following unit cell parameters: a ​= ​10.5437(2) Å in (1) and a ​= ​10.3949(3) Å in (2). The structural features have been investigated, and the distortions of the building blocks [MO6] (M ​= ​Te, W) have been found. The oxidation states of tellurium have been confirmed by X-ray photoelectron spectroscopy. The thermal behavior of obtained compounds has been studied. [Display omitted] •CsTe1.625W0.375O6 and RbTe1.5W0.5O6 homogeneous single crystals have been grown.•The crystal structures of CsTe1.625W0.375O6 and RbTe1.5W0.5O6 have been studied.•Thermal behavior of CsTe1.625W0.375O6 and RbTe1.5W0.5O6 has been investigated.•The tellurium with the mixed oxidation state has been found.•The stabilization reasons of cubic mixed-valence tellurium β-pyrochlore CsTe2O6-x have been discussed.