Thermal structural properties of calcium tungstate

The results of in situ temperature-resolved powder diffraction studies of CaWO4 scheelite 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 WO4 complexes have been analysed in terms of bond distances, interatomic angles and anisotropic displacement parameters. The WO4 2- 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 WO4 complexes is the primary reason for the anisotropy of thermal expansion in calcium tungstate. © 2011 International Union of Crystallography Printed in Singapore - all rights reserved