Structural study of La_0.75Sr_0.25CrO₃ at high temperatures

Abstract

A high-temperature neutron diffraction study has been carried out on La_0.75Sr_0.25CrO₃ compound in the temperature range 300–1400 K. On doping the parent compound LaCrO₃ with Sr at the La site, the orthorhombic (Pbnm) to rhombohedral (R3c) structural transition shifts to lower temperatures. From quantitative Rietveld analysis it is found unequivocally that there is a two-phase coexistence (orthorhombic and rhombohedral phases with ~89 and 11 weight%, respectively) in the temperature range 300–470 K and a three-phase coexistence (with a new cubic phase with space group Pm3m) in the temperature range 480–1400 K. The weight percentages of the orthorhombic, rhombohedral and cubic phases were found to be ∼49%, 37% and 14%, respectively, in the temperature range 480–1300 K, while over 1350–1400 K, the average weight percentages of orthorhombic, rhombohedral and cubic phases were found to be ∼41%, 41% and 18%, respectively. The coefficients of volume thermal expansion and linear thermal expansion have been determined for all three phases. The importance of the present study has been discussed for practical applications of the studied compound in solid oxide fuel cells.