Mechanical behavior of rare‐earth orthophosphates near the monazite/xenotime boundary characterized by nanoindentation

Taylor M. Wilkinson, Dong Wu, Matthew A. Musselman, Nan Li, Nathan Mara, Corinne E. Packard

Research output: Contribution to journalArticlepeer-review

9 Scopus citations

Abstract

Low elastic modulus and hardness, as well as anomalous indentation behavior, have been observed during indentation of xenotime rare-earth orthophosphate ceramics (REPO4s) with compositions near the monazite/xenotime phase boundary. Pressure-induced phase transformation has been identified as a potential cause for both observations. This study comprehensively characterizes the mechanical properties and indentation behavior of four elemental REPO4 materials (EuPO4, GdPO4, TbPO4, and DyPO4) that span the monazite/xenotime phase boundary using ex situ nanoindentation for a range of loading rates and indentation depths. In situ nanoindentation within a SEM was used to correlate discrete load-depth behavior to the development of surface features. Anomalous, elbow-type behavior was not restricted to xenotimes, but occurred in all four materials; thus we concluded that the presence of an elbow in the indentation data was not a unique identifier of phase transformation in rare-earth orthophosphates. Furthermore, it was shown that the elastic modulus of each of these compositions approached the value predicted by simulations and hardness was consistently above 5 GPa, provided that the samples were processed to nearly full density.

Original languageEnglish (US)
Pages (from-to)203-210
Number of pages8
JournalMaterials Science and Engineering: A
Volume691
DOIs
StatePublished - Apr 13 2017

Bibliographical note

Publisher Copyright:
© 2017 Elsevier B.V.

Keywords

  • Ceramics
  • Mechanical characterization
  • Nanoindentation
  • Phase transformation
  • Twinning

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