Investigation of the α-Fe⇌ε-Fe Phase Transition by Synchrotron Radiation

  1. Murli H. Manghnani and
  2. Yasuhiko Syono
  1. Murli H. Manghnani,
  2. Li Chung Ming and
  3. Nobuyuki Nakagiri

Published Online: 21 MAR 2013

DOI: 10.1029/GM039p0155

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto

How to Cite

Manghnani, M. H., Ming, L. C. and Nakagiri, N. (1987) Investigation of the α-Fe⇌ε-Fe Phase Transition by Synchrotron Radiation, in High-Pressure Research in Mineral Physics: A Volume in Honor of Syun-iti Akimoto (eds M. H. Manghnani and Y. Syono), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM039p0155

Author Information

  1. Hawaii Institute of Geophysics, University of Hawaii, Honolulu, Hawaii 96822, USA

Publication History

  1. Published Online: 21 MAR 2013
  2. Published Print: 1 JAN 1987

ISBN Information

Print ISBN: 9780875900667

Online ISBN: 9781118664124

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Keywords:

  • Mineralogy and Crystal Chemistry;
  • Phase transformations;
  • High Pressure-High Temperature Research

Summary

The α(bcc)⇌ε(hcp) transition in iron was investigated in situ under simultaneously high pressure and temperature (to ∼27.5 GPa and 540°C) in a diamond-anvil cell using synchrotron radiation and the energy-dispersive X-ray diffraction technique. The data for five isothermal runs (at 190, 270, 360, 450, and 540 °C) were interpreted on the basis of the intensity ratio of the ε-Fe(101) peak and the overlapped {ε-Fe(002)+α-Fe(110)} peak to constrain the pressures for the starts of the α[RIGHTWARDS ARROW]ε and ε[RIGHTWARDS ARROW]α transitions (i.e., [UEQU], respectively). The resultant “equilibrium” dT/dP slope is approximately −435 deg/GPa (dP/dT=−0.0023 GPa/deg).

The isothermal P-V relationships for the α-Fe and ε-Fe phases at temperatures up to 442°C were deduced to yield the coefficients of volumetric thermal expansion as a function of pressure as αν(deg−1×105)=(5.53±0.04)−(0.070±0.006)P (GPa) for the α-phase, and αν(deg−1×105)=(5.29±0.13)−(0.090±0.009)P (GPa) for the ε-phase, resulting in a lower value of αν for the ε-phase at any given pressure.