Thermal Expansion Properties of A-Site Deficient La(Sr)CrO3

Thermal expansion characteristics of A-site deficient Sr-doped lanthanum chromites, La1-xSrxCr1.01O3-δ (x=0.02, 0.03, 0.05, 0.10, 0.13, 0.15), have been studied in air and in a reducing atmosphere (log PO2=-16) from room temperature to 1000°C. The phase transition from orthorhombic to rhombohedral, accompanying linear contraction, was respectively observed for samples with x=0.02 to 0.10 both in air and in the reducing atmosphere. The phase transition temperature was found to shift downwards with increase in Sr content. Samples with x=0.10 to 0.15 in air and a sample with x=0.13 in the reducing atmosphere gave expansion coefficients comparable to that of 8mol% Y2O3-stabilized ZrO2 (YSZ). In the reducing atmosphere, the thermal expansion coefficients of the samples with x=0.10 to 0.15 remarkably increased in the vicinity of 1000°C due to generation of oxygen vacancies.