Thermoelastic properties of chromium oxide Cr2O3 (eskolaite) at high pressures and temperatures

Anna M. Dymshits, Peter I. Dorogokupets, Igor S. Sharygin, Konstantin D. Litasov, Anton Shatskiy, Sergey V. Rashchenko, Eiji Ohtani, Akio Suzuki, Yuji Higo

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A new synchrotron X-ray diffraction study of chromium oxide Cr2O3 (eskolaite) with the corundum-type structure has been carried out in a Kawai-type multi-anvil apparatus to pressure of 15 GPa and temperatures of 1873 K. Fitting the Birch–Murnaghan equation of state (EoS) with the present data up to 15 GPa yielded: bulk modulus (K0,T0), 206 ± 4 GPa; its pressure derivative K′0,T, 4.4 ± 0.8; (∂K0,T/∂T) = ‒0.037 ± 0.006 GPa K‒1; a = 2.98 ± 0.14 × 10−5 K−1 and b = 0.47 ± 0.28 × 10‒8 K‒2, where α0,T = a + bT is the volumetric thermal expansion coefficient. The thermal expansion of Cr2O3 was additionally measured at the high-temperature powder diffraction experiment at ambient pressure and α0,T0 was determined to be 2.95 × 10−5 K−1. The results indicate that coefficient of the thermal expansion calculated from the EoS appeared to be high-precision because it is consistent with the data obtained at 1 atm. However, our results contradict α0 value suggested by Rigby et al. (Brit Ceram Trans J 45:137–148, 1946) widely used in many physical and geological databases. Fitting the Mie–Grüneisen–Debye EoS with the present ambient and high-pressure data yielded the following parameters: K0,T0 = 205 ± 3 GPa, K′0,T = 4.0, Grüneisen parameter (γ0) = 1.42 ± 0.80, q = 1.82 ± 0.56. The thermoelastic parameters indicate that Cr2O3 undergoes near isotropic compression at room and high temperatures up to 15 GPa. Cr2O3 is shown to be stable in this pressure range and adopts the corundum-type structure. Using obtained thermoelastic parameters, we calculated the reaction boundary of knorringite formation from enstatite and eskolaite. The Clapeyron slope (with d P/ d T= - 0.014 GPa/K) was found to be consistent with experimental data.

Original languageEnglish
Pages (from-to)447-458
Number of pages12
JournalPhysics and Chemistry of Minerals
Issue number6
Publication statusPublished - 2016 Jun 1


  • Chromium oxide
  • Eskolaite
  • Experiment
  • High pressure
  • Knorringite formation
  • Thermal equation of state
  • Thermal expansion


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