Neutron diffraction study of the crystal structure and structural phase transition of La0.7Ca0.3−xSrxCrO3 (0≤x≤0.3): The relationship between thermodynamic behavior and crystal structure changes at the phase transition |
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Authors: | Kazuki Omoto Steve Hull Takuya Hashimoto |
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Institution: | a Department of Integrated Sciences in Physics and Biology, College of Humanities and Sciences, Nihon University, 3-25-40 Sakurajousui, Setagaya-ku, Tokyo 156-8550, Japan b Department of Chemical and Biological Engineering, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden c The ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, UK |
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Abstract: | The crystal structure of the La0.7Ca0.3−xSrxCrO3 series, including the compositional and temperature dependence of the structural parameters, has been studied by variable temperature neutron diffraction measurements. The extent of the distortions from the ideal cubic perovskite structure has been evaluated quantitatively using the average bond lengths and the mean volumes of the CrO6] octahedron and (La/Ca/Sr)O12] polyhedron, and has been shown to decrease with increase of Sr content or temperature. At the structural phase transition from the orthorhombic (Pnma) structure to the rhombohedral one, the volume of the CrO6] octahedron decreases whereas that of the (La/Ca/Sr)O12] polyhedron shows little difference, resulting in an overall decrease in the level of distortion. The change in the degree of distortion at the phase transition decreases with increase of Sr content, in agreement with the smaller variation of the enthalpy and volume for the specimens with higher Sr content. |
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Keywords: | La0 7Ca0 3-x SrxCrO3 Interconnector Solid oxide fuel cells Structural phase transition Neutron diffraction Rietveld refinement |
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