• journal_title：American Mineralogist
• Contributor：Kei Hirose ; Katsuyuki Kawamura ; Yasuo Ohishi ; Shigehiko Tateno ; Nagayoshi Sata
• Publisher：Mineralogical Society of America
• Date：2005-
• Format：text/html
• Language：en
• Identifier：10.2138/am.2005.1702
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：90
• issue：1
• firstpage：262
• section：Letters

A phase transition of MgGeO₃ perovskite was examined at high-pressure and -temperature using synchrotron X-ray diffraction measurements. The results demonstrate that it transforms to a CaIrO₃-type post-perovskite phase above 63 GPa at 1800 K. The density increase is 1.5% at the transition pressure. These observations confirm that MgGeO₃ is a low-pressure analogue to MgSiO₃, for which a similar phase transition was recently found above 125 GPa and 2500 K. The unit-cell parameters of MgGeO₃ post-perovskite phase obtained at 300 K during decompression from 79 to 6 GPa show that the b-axis is significantly more compressible than are the a- and c-axes, which could be due to the GeO₆-octahedral sheet stacking structure along b. The bulk modulus was determined to be K₀ = 192(±5) GPa with a fixed pressure derivative of the bulk modulus, K′, of 4.