Analysis of phase transition behavior of BaCeO3 with thermal analyses and high temperature X-ray diffraction

Structural phase transitions in BaCeO3 have been investigated with combination of differential scanning calorimetry (DSC), dilatometry and high temperature X-ray diffraction with high sensitivity and resolution. In DSC curve at heating procedures, baseline shift, endothermic peak and another baseline shift were observed at 260 degrees C, 385 degrees C and 895 degrees C, respectively. From DSC curve at cooling procedure, it was revealed that all the baseline shifts and peak were reversible. No hysteresis was observed in the both baseline shifts indicating second order phase transition at 260 degrees C and 895 degrees C with variation of specific heat capacity, Delta C-p, of 10 J/mol K and 7 J/mol K, respectively; whereas the order of the phase transition at 385 degrees C was revealed to be the first since hysteresis was detected around 370-385 degrees C. Variation of enthalpy, Delta H, at the phase transition was 45 J/mol. High temperature X-ray diffraction measurements have revealed that the crystal structure of BaCeO3 changes from primitive orthorhombic perovskite through body-centered one, rhombohedral distorted one to cubic one around 280 degrees C, 400 degrees C and 900 degrees C, showing correspondence with DSC curves. Dependence of molar volume on temperature estimated from high temperature X-ray diffraction showed agreement with thermal expansion behavior observed with dilatometry. (c) 2009 Elsevier B.V. All rights reserved.