X-ray diffraction studies and phase transformations of CeNbO 4+ δ using in situ techniques

Abstract

Investigation of CeNbO 4± δ has revealed that the previously determined phase transformations should be revised. Whereas previous studies have indicated that a reduced tetragonal modification of CeNbO 4 is produced on heating in vacuum the present study shows no evidence for this phase transformation. In contrast, a monoclinic–tetragonal phase transformation on heating in air was observed, indicating that the high temperature phase (∼800 °C) was a stable, oxygen excess tetragonal phase with a similar structure to the Scheelite mineral, CaWO 4. Lattice parameters for this phase were calculated to be a=5.3839(1) Å and c=11.6168(3) Å.