The dependence of thermal expansion on the composition and atmosphere for molybdenumdoped lanthanum-strontium cobaltite La0.6Sr0.4Co1−xMoxO3−δ (х = 0–0.10) was studied by in situ hightemperature X-ray diffraction method (HTXRD). The linear coefficients of thermal expansion (CTE) were determined in air in the temperature range of 30–750°C. The linear dependence of the unit cell parameters on the molybdenum content was observed for the entire range of compositions, which obeys Vegard’s law and indicates the formation of solid solutions.
