Measurement of thermal expansion coefficient of LaCrO3

Thermal expansion coefficients of LaCrO3 and Al2O3 were measured using a push-rod type dilatometer in the temperature range from 100 to 873 K. The error of the measurement depending on the position of the thermocouple in the dilatometer was also investigated. The thermal expansion coefficient of Al2O3 in the temperature range from 100 to 873 K generally agreed with the literature value. Anomalies in the thermal expansion coefficient were observed clearly at 283 and 528.5 K in LaCrO3. The first anomaly is a volume expansion due to the transition from an anti-ferromagnetic to a paramagnetic state, the second one is a volume shrinkage due to the transition from an orthorhombic to a rhombohedral structure. The thermal expansion coefficient measured using the thermocouple on the reference side was about 1% higher than that using the thermocouple attached on the sample. The error of the transition temperature due to the position of the thermocouple was also investigated.