Thermal structural properties of calcium tungstate

Abstract

The results ofin situtemperature-resolved powder diffraction studies of CaWO4scheelite using both synchrotron radiation and neutron scattering are reported. The studies performed over a broad temperature range of 5–1773 K confirm the scheelite type of structure for calcium tungstate over the whole temperature range. The anisotropy of thermal expansion in calcium tungstate as well as the rigidity of WO4complexes have been analysed in terms of bond distances, interatomic angles and anisotropic displacement parameters. The WO42−complex anions showed a remarkable robustness in the whole studied temperature range, thus pointing out that the layered structure formed by two-dimensional CsCl-type arrangements of Ca cations and WO4complexes is the primary reason for the anisotropy of thermal expansion in calcium tungstate.