Crystal structure and the structural disorder of ceria from 40 to 1497 °C

Nuclear-density distribution of ceria (CeO2, space group: Fm3¯m) has been investigated between 40 and 1497 °C by the maximum-entropy method (MEM) and MEM-based pattern fitting combined with the Rietveld method using neutron powder diffraction data. The refined unit-cell and atomic displacement parameters increased with an increase of temperature. The results of the MEM analysis reveal that the oxide ions have a positional disorder spreading over a wide area and shift to the <111> directions from the ideal position 8c 1 / 4,1 / 4,1 / 4 of the fluorite-type structure. The disorder of the oxide ions is more significant at higher temperatures and suggests the diffusion paths in the <111> and <100> directions.