X-ray diffraction studies and phase transformations of CeNbO4+δ using in situ techniques

Investigation of CeNbO4 g has revealed that the previously determined phase transformations should be revised. Whereas previous studies have indicated that a reduced tetragonal modification of CeNbO4 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 (similar to 800 degreesC) was a stable, oxygen excess tetragonal phase with a similar structure to the Scheelite mineral, CaWO4. Lattice parameters for this phase were calculated to be a = 5.3839(1) Angstrom and c = 11.6168(3) Angstrom. (C) 2003 Elsevier SAS. All rights reserved.