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.
Similar content being viewed by others
References
Abrashev MV, Bäckström J, Börjesson L, Popov VN, Chakalov RA, Kolev N, Meng RL, Iliev MN (2002) Raman spectroscopy of CaMnO3: mode assignment and relationship between Raman line intensities and structural distortions. Phys Rev B 65:184301
Akahama Y, Kawamura H (2004) High-pressure Raman spectroscopy of diamond anvils to 250 GPa: method for pressure determination in the multimegabar pressure range. J Appl Phys 96:3748–3751
Chopelas A, Boehler R, Ko T (1994) Thermodynamics and behavior of γ-Mg2SiO4 at high pressure: implications for Mg2SiO4 phase equilibrium. Phys Chem Minerals 21:351–359
Hirai S, Welch MD, Aguado F, Redfern SAT (2009) The crystal structure of CaIrO3 post-perovskite revisited. Z Kristallogr 224:345–350
Hirai S, Sanehira T, Nishiyama N, Irifune T, Klemme S, Bromiley G, Attfield JP (2011) Tuning of structure, morphology and magnetism in postperovskite oxide solid solutions. Chem Mater 23:114–121
Hustoft J, Shim S-H, Kubo A, Nishiyama N (2008) Raman spectroscopy of CaIrO3 postperovskite up to 30 GPa. Am Mineral 93:1654–1658
Inaguma Y, Hasumi K, Yoshida M, Ohba T, Katsumata T (2008) High-pressure synthesis, structure, and characterization of a post-perovskite CaPtO3 with CaIrO3-type structure. Inorg Chem 47:1868–1870
Kojitani H, Furukawa A, Akaogi M (2007a) Thermochemistry and high-pressure equilibria of the post-perovskite phase transition in CaIrO3. Am Mineral 92:229–232
Kojitani H, Shirako Y, Akaogi M (2007b) Post-perovskite phase transition in CaRuO3. Phys Earth Planet Inter 165:127–134
Lindsay-Scott A, Wood IG, Dobson DP, Voˇcadlo L, Brodholt JP, Crichton W, Hanfland M, Taniguchi T (2010) The isothermal equation of state of CaPtO3 post-perovskite to 40 GPa. Phys Earth Planet Inter (to be published)
Martin CD, Chapman KW, Chupas PJ, Prakapenka V, Lee PL, Shastri SD, Parise JB (2007) Compression, thermal expansion, structure, and instability of CaIrO3, the structure model of MgSiO3 post-perovskite. Am Mineral 92:1048–1053
Murakami M, Hirose K, Kawamura K, Sata K, Ohishi Y (2004) Post-perovskite phase transition in MgSiO3. Science 304:855–858
Ogawa S (1976) Electrical resistivity of weak itinerant ferromagnet ZrZn2. J Phys Soc Jpn 40:1007–1009
Ohgushi K, Matsushita Y, Miyajima N, Katsuya Y, Tanaka M, Izumi F, Gotou H, Ueda Y, Yagi T (2008) CaPtO3 as a novel post-perovskite oxide. Phys Chem Miner 35:189–195
Park CI, Condrate RA, Snyder RL (1976) The Raman spectra of perovskite-structured alkaline earth hafnates. Appl Spectr 30:352–353
Santilla′n J, Shim S-H, Shen G, Prakapenka VB (2006) High-pressure phase transition in Mn2O3: application for the crystal structure and preferred orientation of the CaIrO3 type. Geophys Res Lett 33:L15307
Sarkozy RF, Moeller CW, Chamberland BL (1974) The characterization of calcium iridium oxides. J Solid State Chem 9:242–246
Shim S-H (2008) The postperovskite transition. Ann Rev Earth Planet Sci 36:569–599
Shim S-H, Kubo A, Duffy TS (2007) Raman spectroscopy of perovskite and post-perovskite phases of MgGeO3 to 123 GPa. Earth and Planet Sci Lett 260:166–178
Shim S-H, Catalli K, Hustoft J, Kubo A, Prakapenka VB, Caldwell WA, Kunz M (2008) Crystal structure, thermoelastic properties of (Mg0.91Fe0.09)SiO3 postperovskite up to 135 GPa and 2700 K. Proc Natl Acad Sci USA 105:7382–7386
Shim S-H, Bengtson A, Morgan D, Sturhahn W, Catalli K, Zhao J, Lerche M, Prakapenka VB (2009) Electronic and magnetic structures of the postperovskite-type Fe2O3 and implications for planetary magnetic records and deep interiors. Proc Natl Acad Sci USA 106:5508–5512
Shirako Y, Kojitani H, Akaogi M, Yamaura K, Takayama-Muromachi E (2009) High-pressure phase transitions of CaRhO3 perovskite. Phys Chem Miner 36:455–462
Yamaura K, Shirako Y, Kojitani H, Arai M, Young DP, Akaogi M, Nakashima M, Katsumata T, Inaguma Y, Takayama-Muromachi E (2009) Synthesis and magnetic and charge-transport properties of the correlated 4d post-perovskite CaRhO3. J Am Chem Soc 131:2722–2726
Acknowledgments
We acknowledge support from EPSRC and the Leverhulme Trust, UK.
Author information
Authors and Affiliations
Corresponding author
Rights and permissions
About this article
Cite this article
Hirai, S., Kojima, Y., Ohfuji, H. et al. High-pressure Raman studies and heat capacity measurements on the MgSiO3 analogue CaIr0.5Pt0.5O3 . Phys Chem Minerals 38, 631–637 (2011). https://doi.org/10.1007/s00269-011-0435-2
Received:
Accepted:
Published:
Issue Date:
DOI: https://doi.org/10.1007/s00269-011-0435-2