Post-perovskite transitions in CaB^4+O_3 at high pressure
Post-perovskite transitions in CaB^4+O_3 at high pressure
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高压下 CaB^4 O_3 中的后钙钛矿转变
DOI：
10.1088/1742-6596/215/1/012095
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
E
中科院分区：
文献类型：
--
作者：
Akaogi;M.;Shirako;Y.;Kojitani;H.;Takamori;S.;Yamaura;K.;Takayama- Muromachi;E
用多面顶压机研究了CaRhO(Sub3)中的高压相变，最高气压为27 Gpa，温度为1930℃。CaRhO(Sub3)钙钛矿相转变为后钙钛矿相变的中间相为单斜相。钙钛矿-中间相和中间相-后钙钛矿相转变的体积变化分别为-1.1%和-0.7%。CaRhO{sub3}后钙钛矿型氧化物是迄今发现的第四种可淬火的后钙钛矿型氧化物。通过高温量热实验，测得CaRuO{sub3}中钙钛矿-后钙钛矿相变的热焓为15.23.3kJ/mol。结合开罗{sub3}的数据，表明开罗{sub3}钙钛矿的能量稳定性不如CaRuO{sub3}钙钛矿。这与CaRuO{sub3}钙钛矿结构的八面体骨架的倾斜角表明其正交形变大于CaRuO{sub3}的事实是一致的。CaBO{sub3}(B=Ru，Rh，Ir)的钙钛矿-后钙钛矿相变压力随倾斜角的减小几乎呈线性增加，表明钙钛矿-钙钛矿后钙钛矿相变可能是由于钙钛矿结构随压力的不稳定所致。
High-pressure phase transitions in CaRhO{sub 3} were examined using a multianvil apparatus up to 27 GPa and 1930 {sup o}C. CaRhO{sub 3} perovskite transforms to post-perovskite via a monoclinic intermediate phase with increasing pressure. Volume changes for the transitions of perovskite - intermediate phase and of intermediate phase - post-perovskite are -1.1 and -0.7 %, respectively. CaRhO{sub 3} post-perovskite is the fourth quenchable post-perovskite oxide found so far. By high-temperature calorimetric experiments, enthalpy of the perovskite - post-perovskite transition in CaRuO{sub 3} was measured as 15.2{+-}3.3 kJ/mol. Combining the datum with those of CaIrO{sub 3}, it is shown that CaIrO{sub 3} perovskite is energetically less stable than CaRuO{sub 3} perovskite. This is consistent with the fact that orthorhombic distortion of CaIrO{sub 3} perovskite is larger than CaRuO{sub 3}, as indicated with the tilt-angle of octahedral framework of perovskite structure. The transition pressure from perovskite to post-perovskite in CaBO{sub 3} (B = Ru, Rh, Ir) increases almost linearly with decreasing the tilt-angle, suggesting that the perovskite - post-perovskite transition may result from instability of the perovskite structure with pressure.