Crystal structures and phase transitions in Sr2InTaO6 perovskite |
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Authors: | Qingdi Zhou Brendan J Kennedy Maxim Avdeev |
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Institution: | 1. School of Chemistry, The University of Sydney, Sydney, NSW, 2006, Australia 2. Bragg Institute, Australian Nuclear Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW, 2232, Australia
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Abstract: | The preparation and crystal structure of the double perovskite oxide Sr2InTaO6 are reported. This oxide has a monoclinic structure in space group P21/n at room temperature, where In and Ta display a rock-salt type ordering with a = 5.73356(10), b = 5.74052(10), c = 8.10905(14) Å and β = 90.022(6)°. Variable temperature neutron diffraction measurements demonstrate this displays the sequence of phase transitions $ P2_{1} /n\mathop{\longrightarrow}\limits^{{605\,^\circ {\text{C}}}}I2/m\mathop{\longrightarrow}\limits^{{705\,^\circ {\text{C}}}}I4/m\mathop{\longrightarrow}\limits^{{930\,^\circ {\text{C}}}}Fm\bar{3}m $ as a consequence of the sequential loss of tilting of the corner shared octahedra upon heating. The evolution of Sr2InTaO6 crystal structure upon heating is analysed and described in terms of symmetry-adapted distortion modes. The GM4+ and X3+, that are responsible for anti-phase and in-phase tilting, respectively, are highly temperature dependent, with the GM4+ mode having the largest amplitude at room temperature. |
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