• journal_title：American Mineralogist
• Contributor：Jinya Kato ; Kei Hirose ; Haruka Ozawa ; Yasuo Ohishi
• Publisher：Mineralogical Society of America
• Date：2013-02-01
• Format：text/html
• Language：en
• Identifier：10.2138/am.2013.4133
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：98
• issue：2-3
• firstpage：335
• section：Article

Phase transitions in Al₂O₃ between corundum Rh₂O₃(II)-type and CaIrO₃-type (post-perovskitetype) phases were examined at high pressure and high temperature in a laser-heated diamond-anvil cell (DAC) based on in situ X-ray diffraction measurements. The locations of corundum-Rh₂O₃(II) and Rh₂O₃(II)-CaIrO₃ boundaries were precisely determined by conducting both forward and backward reaction experiments. The results demonstrate that corundum undergoes a phase transition to Rh₂O₃(II)-type structure above 106 GPa at 1800 K with a negative Clapeyron slope of –6.5 ± 1.5 MPa/K, generally consistent with earlier experimental and theoretical works. The Rh₂O₃(II)-type phase further transforms into CaIrO₃-type above 170 GPa at 2300 K, indicating the transition pressure much higher than earlier experimental work but in agreement with reported GGA calculations. The Clapeyron slope of this phase transition was found to be high negative (–20 ± 5 MPa/K).