Abstract

The La_1 − xSr_xSc_1 − yFe_yO_3 − δ (LSSF) samples were prepared by solid state reaction with heat treatment at 1300 °C and subsequent sintering at 1500 °C. Hydration behavior, nonstoichiometry of oxide ions, and conductivity of LSSF were investigated. The results revealed that single phase of LSSF was obtained in a wide composition range after the sintering. The concentrations of hydroxide ions in the LSSF samples hydrated at 300 °C in the atmosphere of 5% H₂O–16% O₂–Ar increased with the increasing Sr content or the decreasing Fe content. No linear relationship between concentration of hydroxide ions and that of oxide ion vacancies was recognized. For example, the concentration of hydroxide ions per unit cell of La_0.8Sr_0.2ScO_2.9 was as high as 1.32 × 10^− 1, but a dramatic drop in the concentration of hydroxide ions was observed by introducing just a small amount of Fe of y = 0.05. The Fe content of LSSF plays an important role in the hydration properties. In addition, the concentrations of hydroxide ions in La_1 − xSr_xCoO_3 − δ (LSC) and La_1 − xSr_xCo_1 − yFe_yO_3 − δ (LSCF) were also measured, and found to be quite low.