Pressure-induced structural transformations in lanthanide titanates: La2TiO5 and Nd2TiO5 |
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Authors: | FX Zhang JW Wang |
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Institution: | Department of Geological Sciences, The University of Michigan, Ann Arbor, MI 48109, USA |
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Abstract: | The structure of orthorhombic rare earth titanates of La2TiO5 and Nd2TiO5, where Ti cations are in five-fold coordination with oxygen, has been studied at high pressures by X-ray diffraction (XRD), Raman scattering measurements, and quantum mechanical calculations. Both XRD and Raman results indicated two pressure-induced phase transitions during the process. An orthorhombic super cell (a×b×2c) formed at a pressure between 6 and 10 GPa, and then transformed to a hexagonal high-pressure phase accompanied by partial decomposition. The hexagonal high-pressure phase is quenchable. Detailed structural analysis indicated that the five-coordinated TiO5 polyhedra remain during the formation of super cell, but the orthorhombic-to-hexagonal phase transition at high pressures is a reconstructive process, and the five-fold Ti-O coordination increased to more than 6. This phase transition sequence was verified by quantum mechanical calculations. |
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Keywords: | RE2TiO5 Superstructure Pressure Phase transition |
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