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GEOPHYSICAL RESEARCH LETTERS, VOL. 33, L15307, doi:10.1029/2006GL026423, 2006

High-pressure phase transition in Mn2O3: Application for the crystal structure and preferred orientation of the CaIrO3 type

Javier Santillán

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA


Sang-Heon Shim

Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA


Guoyin Shen

GSECARS, University of Chicago, Chicago, Illinois, USA


Vitali B. Prakapenka

GSECARS, University of Chicago, Chicago, Illinois, USA


Abstract

Our X-ray diffraction measurements reveal that Mn2O3 undergoes a phase transition to the CaIrO3 type, which is proposed for the post-perovskite in MgSiO3, at 27–38 GPa and 300 K, bypassing the other phase transitions observed in sesquioxides. Small distortions in the polyhedra after the transition indicate that the Jahn-Teller effect, which is strong at ambient conditions, is suppressed during the transition. The CaIrO3-type phase exhibits strong preferred orientation of the (010) plane perpendicular to the loading axis before annealing whereas preferred orientation of the (100) and (110) planes was observed after annealing. The pre-annealing texture may result from either the deformation under strong differential stresses or the phase transition. The post-annealing texture may be related to either lower differential stresses or thermal annealing. Our result shows that the texture of the CaIrO3 type can be sensitive to phase transition and annealing as well as differential stresses.

Received 27 March 2006; accepted 22 June 2006; published 4 August 2006.

Index Terms: 3902 Mineral Physics: Creep and deformation; 3924 Mineral Physics: High-pressure behavior; 3954 Mineral Physics: X-ray, neutron, and electron spectroscopy and diffraction.

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Citation: Santillán, J., S.-H. Shim, G. Shen, and V. B. Prakapenka (2006), High-pressure phase transition in Mn2O3: Application for the crystal structure and preferred orientation of the CaIrO3 type, Geophys. Res. Lett., 33, L15307, doi:10.1029/2006GL026423.