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

摘要

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 ℃) 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) A and c = 11.6168(3) A.