Martensitic Transformation in La_1-xSr_xCoO₃

Abstract

A multiple twin structure was found in single crystals of La 1- x Sr x CoO 3 ( x =0.0, 0.02 and 0.1) by means of an optical microscope and SEM. The width of each domain is about 1∼10 µm. Doubled or quadrupled splitting in Laue spots was observed. The twin structure was explained by a martensitic transformation due to a small rhombohedral distortion. The observed angles and directions of the splitting agreed well with the calculated values. The twin planes were {100} and {110} in the pseudocubic cell. Observation by means of high-temperature optical microscopy revealed that the twin structure did not disappear up to 1000°C. The transformation in La 1- x Sr x CoO 3 is discussed by comparing it with those in LaAlO 3 and NiO.