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Clapeyron slope of the post‐perovskite phase transition in CaIrO 3
Author(s) -
Hirose Kei,
Fujita Yosuke
Publication year - 2005
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2005gl023219
Subject(s) - perovskite (structure) , post perovskite , phase transition , materials science , isostructural , phase boundary , phase (matter) , geology , thermodynamics , mineralogy , transition zone , crystallography , crystal structure , chemistry , geophysics , physics , organic chemistry
The Clapeyron slope of the perovskite to post‐perovskite phase transition has not been well determined experimentally. Crystal structure of CaIrO 3 is equivalent to the MgSiO 3 post‐perovskite phase (space group: Cmcm ) at ambient condition. We have found that perovskite phase ( Pbnm ) of CaIrO 3 , which is isostructural with MgSiO 3 perovskite, is stable at 1–3 GPa and 1400–1550°C. The perovskite to post‐perovskite phase transition in CaIrO 3 was determined by using piston‐cylinder apparatus at 0.9–3.0 GPa and 1350–1550°C. Results show that phase transition pressure is strongly temperature‐sensitive with a Clapeyron slope of +17(±3) MPa/°C. These results, obtained for a suitable analogue material, suggest that post‐perovskite phase transition in MgSiO 3 also has a large positive value of the Clapeyron slope. Such a pronounced exothermic reaction in the Earth's lowermost mantle will promote the upwelling of high‐temperature plumes from the core‐mantle boundary region.