High-Temperature Neutron Powder Diffraction Study of Cerium Dioxide up to 1770K

Abstract

We have investigated the temperature dependence of unit-cell and structural parameters of ceria (cerium dioxide, CeO₂) from room temperature to 1770 K by neutron powder diffraction and the Rietveld method. The unit-cell parameter increases continuously with temperature. It was confirmed that the Debye-Waller factor of oxygen B(O) is larger than that of cerium B(Ce) at any temperature from room temperature to 1770 K. Both B(O) and B(Ce) increase with an increase of temperature. We have also studied the anisotropic thermal vibration of oxide ions in ceria by the combination technique of the Rietveld refinement, the maximum entropy method (MEM) and the MEM-based pattern fitting. The refined position of oxide ion is 0.35(1), 0.35(1), 0.35(1), indicating the shift of oxide ion to the <111> direction leaving from the Ce ions.