Phase transition and abnormal compressibility of lanthanide silicate with the apatite structure

F. X. Zhang, M. Lang, J. M. Zhang, Z. Q. Cheng, Z. X. Liu, J. Lian, and R. C. Ewing
Phys. Rev. B 85, 214116 – Published 18 June 2012

Abstract

The lanthanide silicate La9.33Si6O26, which has the hexagonal apatite structure (P63/m), was investigated at high pressure. A subtle phase transition was observed at ∼13.3 GPa by in situ synchrotron x-ray diffraction and confirmed by infrared absorption and Raman scattering measurements. The high-pressure phase has a structure similar to that of the initial hexagonal apatite structure, but the symmetry is reduced to P63 through the displacement of one oxygen site and tilting of the SiO4 tetrahedra. Interestingly, the high-pressure phase has an abnormally lower compressibility, which is caused by the change in symmetry that allows the tilting of the SiO4 tetrahedra, and the bulk modulus of the high-pressure phase is only half that of the apatite structure.

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  • Received 3 April 2012

DOI:https://doi.org/10.1103/PhysRevB.85.214116

©2012 American Physical Society

Authors & Affiliations

F. X. Zhang1,*, M. Lang1, J. M. Zhang1, Z. Q. Cheng2, Z. X. Liu3, J. Lian4, and R. C. Ewing1,†

  • 1Department of Earth and Environmental Sciences, University of Michigan, Ann Arbor, Michigan 48109
  • 2Department of Geosciences, SUNY, Stony Brook, New York 11794
  • 3Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015
  • 4Department of Mechanical, Aerospace, and Nuclear Engineering, Rensselaer Polytechnic Institute, Troy, New York 12180

  • *zhangfx@umich.edu
  • rodewing@umich.edu

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Vol. 85, Iss. 21 — 1 June 2012

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