Order/Disorder and in Situ Oxide Defect Control in the Bixbyite Phase YPrO3+δ (0 ≤ δ < 0.5).

The YPrO3+δ system is a nearly ideal model system for the investigation of oxide defect creation and annihilation in oxide ion conductor related phases with potential applications as solid state electrolytes in solid oxide fuel cells. The formation, structure, high temperature reactivity, and magnetic susceptibility of phase pure YPrO3+δ (0 ≤ δ ≤ 0.46) are reported. The topotactic reduction and oxidation of the YPrO3+δ system was investigated by powder X-ray in situ diffraction experiments and revealed bixbyite structures (space group: Ia3) throughout the series. Combined neutron and X-ray data clearly show oxygen uptake and removal. The research provides a detailed picture of the Y3+/Pr3+/Pr4+ sublattice evolution in response to the redox chemistry. Upon oxidation, cation site splitting is observed where the cation in the (1/4, 1/4, 1/4) position migrates along the body diagonal to the (x, x, x) position. Any oxygen in excess of YPrO3.0 is located in the additional 16c site without depopulating the orig...