Oxygen trapping and cation site-splitting in Y(2−x)PrxO3+δ (0.0≤x

Abstract

The reduction and oxidation of the solid solution Y2−xPrxO3+δ (0.0≤x<2.0 and δ≤1.0) is investigated with emphasis on potential solid state electrolyte applications in solid oxide fuel cells. The fully reduced solid solution Y2−xPrxO3 (0.0≤x<2.0) crystallizes in the bixbyite structure (Ia3¯). The oxidized solid solution Y2−xPrxO3+δ (0.0≤x<1.4) forms bixbyite phases (Ia3¯) whereas Y2−xPrxO3+δ (1.4≤x<2) compositions form fully disordered defect fluorite structures (Fm3¯m) with variable oxide defect concentrations. The two cation positions are investigated in detail using synchrotron powder X-ray and time of flight neutron diffraction data. In the bixbyite structures the 8c cation site splits into the 16c cation site and the 24d cation position migrates toward the ideal fluorite coordination upon oxidation. Reductive in-situ diffraction experiments reveal the co-existence of the fluorite and bixbyite structure only in a narrow temperature range. During oxidation of the bixbyite phase a new 16c oxide anion site is populated. The impact of the 16c oxide site population on the cation sublattice is being discussed.