Simultaneous high‐P, high‐T X ray diffraction study of β‐(Mg,Fe)2SiO4 to 26 GPa and 900 K

Authors:
  • YFYingwei Fei
    Yingwei Fei
  • HMHo‐Kwang Mao
    Ho‐Kwang Mao
  • JSJinfu Shu
    Jinfu Shu
  • GPG. Parthasarathy
    G. Parthasarathy
  • WBW. A. Bassett
    W. A. Bassett
  • JKJaidong Ko
    Jaidong Ko
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Abstract
The lattice parameters of β phase [(Mg0.84Fe0.16)2SiO4] have been determined by X ray diffraction using synchrotron radiation under simultaneous high‐pressure and high‐temperature conditions. The experiments were conducted up to a pressure of 26 GPa and a temperature of 900 K. High pressures were generated in a Mao‐Bell type diamond anvil cell using neon gas as pressure medium. The sample was heated with an external Ni80Cr20 wire heater. Gold was used as an internal high‐pressure calibrant at high temperatures. Using 4.0 for (∂KT/∂P)T, we found that the 300‐K isothermal bulk modulus, KT0, and its temperature derivative at constant pressure, (∂KT/∂T)P, are 174(±3) GPa and −2.7(±0.3)×10−2 GPa/K, respectively. The value of the Anderson‐Grüneisen parameter δT of the β phase is 5.1(±0.8) above the Debye temperature. The experimental results provide direct measurements of the pressure effect on the thermal expansivity and the temperature dependence of bulk modulus for the β phase.

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