Abstract
The high-pressure behavior of α-Fe2O3 has been studied under static compression up to 60 GPa, using a laser-heated diamond anvil cell. Synchrotron-based angular-dispersive X-ray diffraction shows that the sample remains in the corundum structure up to 50 GPa, but with the appearance of coexisting diffraction lines from a high-pressure phase at pressures above 45 GPa. A least-squares fit of low-pressure phase data to an Eulerian finite-strain equation of state yields linear incompressibilities of K a 0=749.5 (± 18.4) GPa and K c 0= 455.7 (± 21.4) GPa, differing by a factor of 1.6 along the two directions. The enhanced compressibility of the c axis may lead to breaking of vertex- or edge-sharing bonds between octahedra, inducing the high-pressure phase transformation at 50 GPa. Analysis of linear compressibilities suggests that the high-pressure phase above 50 GPa is of the Rh2O3 (II) structure. Continuous laser heating reveals a new structural phase transformation of α-Fe2O3 at 22 GPa, to an orthorhombic structure with a=7.305(3) Å, b=7.850(3) Å, and c=12.877(14) Å, different from the Rh2O3 (II) structure.
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Acknowledgments.
We thank J. H. Ngyuen, K.-J. Kim, N. Funamori, A. Kavner, S. Akber, K. Lee, and H. Scott for help during this project, and SSRL staff for technical assistance. We also thank M.S.T. Bukowinski and M.P. Pasternak for helpful discussions. This work was supported by the National Science Foundation and University of California, and Stanford Synchrotron Radiation Laboratory is funded by the Department of Energy.
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Liu , H., Caldwell, W., Benedetti, L. et al. Static compression of α-Fe2O3: linear incompressibility of lattice parameters and high-pressure transformations. Phys Chem Minerals 30, 582–588 (2003). https://doi.org/10.1007/s00269-003-0351-1
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DOI: https://doi.org/10.1007/s00269-003-0351-1