It was noted that the high-temperature oxide, phase-stabilized with lanthanide dopants, exhibited an order-disorder transition of the anion sub-lattice at about 600C. When annealed at temperatures below the transition temperature, the O-ion conductivity underwent decay. Neutron diffraction studies were performed in order to investigate the structural changes in the anion sub-lattice which resulted in the conductivity decay, and the effect of the dopant on the decay kinetics. The atomic displacement parameters of O ions were determined at low temperatures, for the ordered and disordered structures, in order to determine the static disorder in the O sub-lattice of ordered and disordered structures.

Neutron Diffraction Study of Occupancy and Positional Order of Oxygen Ions in Phase-Stabilized Cubic Bismuth Oxides. S.Boyapati, E.D.Wachsman, B.C.Chakoumakos: Solid State Ionics, 2001, 138[3-4], 293-304