Structural modifications of CaGeO3-wollastonite under room temperature pressurization |
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Authors: | Takaya Nagai Takamitsu Yamanaka |
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Institution: | (1) Department of Earth and Space Science, Faculty of Science, Osaka University 1–16 Machikaneyama, Toyonaka, Osaka 560, Japan Fax: +81-(0)6-850-5817; e-mail: takaya@setc.wani.osaka-u.ac.jp, JP |
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Abstract: | In-situ X-ray diffraction measurements of CaGeO3-wollastonite at high pressure at room temperature have been performed using a diamond anvil cell with an X-ray source. A
new structural modification of CaGeO3-wollastonite is observed at about 6GPa and the characteristic reflections of the high pressure form are preserved on decompression
to an ambient pressure. A rhodonite-like structure is proposed as a high pressure form from the crystal chemical consideration.
The rhodonite-like phase is further transformed into a perovskite-form at about 15 GPa. The rhodonite-like-form of CaGeO3 seems not to be a stable phase from the heating experiments under high pressures. The metastable transition path from the
wollastonite to the perovskite polymorph through the rhodonite-like structure is kinetically favored under room temperature
pressurization. No pressure-induced amorphization is observed during the transition into the perovskite-form, although the
transition is accompanied by the coordination change of Ge atoms from fourfold to sixfold.
Received: July 19, 1995 / Revised, accepted: August 1996 |
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