Structural Phase Transition of Orthorhombic LaCrO3 Studied by Neutron Powder Diffraction

An orthorhombic to a rhombohedral structural phase transition of LaCrO3 has been studied by the neutron powder diffraction over the temperature range of 295–1013 K. At the phase transition around 260°C, the negative volume expansion was observed, and the amount of the volume compression was estimated to be −0.081375 Å3 (−0.138%) per formula unit. The coefficients of volume thermal expansion, −(1/V)/∂V/∂T), were estimated to be 2.285(16)×10−5 K−1 and 2.842(12)×10−5 K−1 for the orthorhombic and rhombohedral phases, respectively. The Rietveld refinement revealed that the volume compression at the phase transition was principally due to the shrinking of the [CrO6] octahedra.