Revisiting the thermal and chemical expansion and stability of La0.6Sr0.4FeO3−δ
Christopher de Leeuwe, Wenting Hu, Dragos Neagu, Evangelos I. Papaioannou, Stevin S. Pramana, B. Ray, John S. O. Evans, Ian S. Metcalfe
Abstract
The thermal and chemical expansivity of La1-xSrxFeO3-δ (x = 0.4) was measured using in situ powder neutron and synchrotron X-ray diffraction at temperatures between 932 K and 1170 K and oxygen partial pressures, PO2, between 10−19 bar and 0.1 bar, giving a wide range of oxygen non-stoichiometry from δ = 0.05 to 0.22. Changes in δ were measured independently using gas analysis. This PO2 and temperature range covers the material’s use as a chemical looping oxygen carrier, a sensor material and in solid oxide fuel cells. Thermal and chemical expansivities were found to be dependent on the oxygen non-stoichiometry, δ. For δ < 0.2 and T = 932–1050 K, the linear thermal expansivity was 5.72(4) × 10−5 Å/K and the linear chemical expansivity was 0.144(9) Å per unit change in δ. For δ > 0.2 and T = 973–1173 K, the linear thermal expansivity increases to 6.18(8) × 10−5 Å/K. For δ > 0.2, the linear chemical expansivity varies with both δ and temperature.