Abstract
Raman spectroscopy and heat capacity measurements have been used to study the post-perovskite phase of CaIr0.5Pt0.5O3, recovered from synthesis at a pressure of 15 GPa. Laser heating CaIr0.5Pt0.5O3 to 1,900 K at 60 GPa produces a new perovskite phase which is not recoverable and reverts to the post-perovskite polymorph between 20 and 9 GPa on decompression. This implies that Pt-rich CaIr1-xPtxO3 perovskites including the end member CaPtO3 cannot easily be recovered to ambient pressure from high P-T synthesis. We estimate an increase in the thermodynamic Grüneisen parameter across the post-perovskite to perovskite transition of 34%, of similar magnitude to those for (Mg,Fe)SiO3 and MgGeO3, suggesting that CaIr0.5Pt0.5O3 is a promising analogue for experimental studies of the competition in energetics between perovskite and post-perovskite phases of magnesium silicates in Earth's lowermost mantle. Low-temperature heat capacity measurements show that CaIrO3 has a significant Sommerfeld coefficient of 11.7 mJ/mol K2 and an entropy change of only 1.1% of Rln2 at the 108 K Curie transition, consistent with the near-itinerant electron magnetism. Heat capacity results for post-perovskite CaIr0. 5Rh0.5O3 are also reported.
Original language | English |
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Pages (from-to) | 631-637 |
Number of pages | 7 |
Journal | Physics and Chemistry of Minerals |
Volume | 38 |
Issue number | 8 |
DOIs | |
Publication status | Published - 2011 Sep |
Externally published | Yes |
Keywords
- High pressure
- Perovskite
- Post-perovskite
- Raman spectroscopy
ASJC Scopus subject areas
- Materials Science(all)
- Geochemistry and Petrology