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 degreesC, the negative vo lume expansion was observed, and the amount of the volume compression was e stimated to be -0.081375 Angstrom (3) (-0.138%) per formula unit. The coeff icients of volume thermal expansion, -(1/V)/(partial derivativeV/partial de rivativeT), were estimated to be 2,285(16)x10(-5) K-1 and 2.842(12)x10(-5) K-1 for the orthorhombic and rhombohedral phases, respectively, The Rietvel d refinement revealed that the volume compression at the phase transition w as principally due to the shrinking of the [CrO6] octahedra. (C) 2000 Acade mic Press.