Crystal structures and phase transition in the system SrTiO3-La2/3TiO3 |
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| Authors: | Christopher J Howard Gregory R Lumpkin Ronald I Smith |
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| Institution: | a Australian Nuclear Science and Technology Organisation, Private Mail Bag 1, Menai NSW 2234, Australiab Department of Earth Sciences, University of Cambridge, Downing Street, Cambridge CB2 3EQ, UKc ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX, UK |
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| Abstract: | The distribution of A-site cations in the perovskite system LaxSr1−3x/2TiO3 depends on the concentration of La3+ ions and associated vacancies. For small x (x?0.2), the substitutions are expected to be random. For x?0.55, the cations are ordered in such a way that successive layers of A-sites are occupied to greater and lesser degree, and this ordering drives a tetragonal distortion. For x from about 0.3 to 0.5, the X-ray patterns show diffuse peaks indicative of similar ordering, but this is not long-range order and no tetragonal distortion results. The lower temperature structures also exhibit out-of-phase tilting of the TiO6 octahedra, setting in at temperatures varying linearly with composition from 105 K for x=0, to about 650 K at x=2/3. |
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| Keywords: | Perovskites Cation/vacancy ordering Synchrotron X-ray diffraction Neutron powder diffraction |
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