Thermal and chemical lattice expansibility of La_0.6Sr _0.4Co_1-yFe_yO_{3 - δ} (y = 0.2, 0.4, 0.6 and 0.8)

Change in the lattice parameters of La_0.6Sr_0.4Co _{1 - y}Fe_yO_{3 - δ} (y = 0.2, 0.4, 0.6 and 0.8) was observed by in-situ XRD under the various temperature and oxygen partial pressure conditions for thermo-chemical expansivity study. By combination of the lattice parameters and oxygen non-stoichiometry, the linear thermal expansion rates were formulated in each compound. The obtained formulas are expressed as a linear function of temperature and oxygen deficiency with the standard deviations from measured data less than 1.2%. Based on the formulas, apparent thermal expansions were separated into thermally induced part and chemically induced part. Thermal expansion coefficient α_th, which is proportional constant for temperature, is increased with increasing Co content in La_0.6Sr_0.4Co_{1 - y}Fe _yO_{3 - δ} while chemical expansion coefficient α_chem, which is proportional constant for oxygen deficiency, shows very small dependence on the composition. Increase in apparent thermal expansion with increasing Co content in La_0.6Sr_0.4Co _{1 - y}Fe_yO_{3 - δ} was caused by the combination of α_th and α_chem.