High-pressure Raman studies and heat capacity measurements on the MgSiO 3 analogue CaIr 0.5 Pt 0.5 O 3

Shigeto Hirai, Yohei Kojima, Hiroaki Ohfuji, Norimasa Nishiyama, Tetsuo Irifune, Stephan Klemme, Geoffrey Bromiley, J. Paul Attfield

Research output: Contribution to journalArticlepeer-review

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 languageEnglish
Pages (from-to)631-637
Number of pages7
JournalPhysics and Chemistry of Minerals
Volume38
Issue number8
DOIs
Publication statusPublished - 2011 Sep
Externally publishedYes

Keywords

  • High pressure
  • Perovskite
  • Post-perovskite
  • Raman spectroscopy

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology

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