Low- and high-temperature single crystal X-ray diffraction study of CaGeO3 perovskite synthesized at 12 GPa and 1253 K
Abstract
The perovskite (pv) phase of CaGeO3 has the Pbnm structure (orthorhombic) at ambient condition and is the best analogue of MgSiO3 pv, a major constituent of the earth's lower mantle. The CaGeO3 pv was previously reported to undergo the phase transition to the Cmcm structure (orthorhombic) at 520 K. However, there is some doubt as for the existence of this high- T phase, and the structural behavior of the Pbnm phase at high- T is also unclear. Clarifying these is important to help the crystal chemical understanding of MgSiO3 pv in the lower mantle. For this purpose, we have conducted the single crystal X-ray diffraction study of CaGeO3 pv in the range from 98 to 873 K. The crystal structures were successfully refined in the Pbnm structure up to 873 K, and the R-factors reached R = 0.0142 -0.0229 and wR = 0.0117 -0.0184 for each temperature. The structural parameters, such as lattice constants and volume, varied monotonously with temperature. No phase transition was thus observed in the investigated temperature range. The further detailed structural properties of CaGeO3 pv at high- T will be discussed.
- Publication:
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APS Shock Compression of Condensed Matter Meeting Abstracts
- Pub Date:
- June 2013
- Bibcode:
- 2013APS..SHK.F1047N