Get access

In Situ Synchrotron X-Ray Diffraction Study of the Cubic to Rhombohedral Phase Transformation in Ln6WO12 (Ln = Y, Ho, Er, Yb)

Authors

  • Zlatomir D. Apostolov,

    1. Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
    Search for more papers by this author
  • Pankaj Sarin,

    1. Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
    Search for more papers by this author
    • Member, The American Ceramic Society.
  • Ryan P. Haggerty,

    Current affiliation:
    1. Sandia National Laboratories, Albuquerque, New Mexico
    Search for more papers by this author
  • Waltraud M. Kriven

    Corresponding author
    • Department of Material Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois
    Search for more papers by this author
    • Member, The American Ceramic Society.
    • Fellow, The American Ceramic Society.

Author to whom correspondence should be addressed. e-mail: kriven@illinois.edu

Abstract

The fcc-to-rhombohedral phase transformation in Ln6WO12 (Ln = Y, Ho, Er, Yb) was investigated by in situ high-temperature X-ray diffraction. The transformation was determined to be an irreversible, first-order, diffusional ordering process, which occurred over a temperature range starting at 1240°C. The transformation can be described as a shape change in the rhombohedral unit cell in the parent fcc phase, determined as elongation along the [111] axis and contraction in the (111) plane, resulting in an overall volume decrease on heating. A discontinuity in both volume per formula unit and rhombohedral angle α was observed across the transformation region for all four compositions. Trends in lattice parameters, ΔV and Δα at room and transformation temperatures were established according to Ln cation type and were found to closely mirror the cationic radii sequence of the corresponding rare earth elements.

Get access to the full text of this article

Ancillary