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Title: Phase transformations and indications for acoustic mode softening in Tb-Gd orthophosphate

At ambient conditions the anhydrous rare-earth orthophosphates assume either the xenotime (zircon) or the monazite structure, with the latter favored for the heavier rare earths. Tb 0.5Gd 0.5PO 4 assumes the xenotime structure at ambient conditions but is at the border between the xenotime and monazite structures. Here we show that, at high pressure, Tb 0.5Gd 0.5PO 4 does not transform directly to monazite but through an intermediate anhydrite-type structure. We show softening of (c 1133 + c 1313) combined elastic moduli close to the transition from the anhydrite to the monazite structure. Stress response of rare-earth orthophosphate ceramics can be affected by both formation of the anhydrite-type phase and the elastic softening in the vicinity of the monazite-phase. In conclusion, we report the first structural data for an anhydrite-type rare earth orthophosphate.
 [1] ;  [2] ;  [2] ;  [3]
  1. Univ. of Nevada, Las Vegas, NV (United States). Dept. of Geoscience and High Pressure Science and Engineering Center
  2. Univ. of California, Davis, CA (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science & Technology Division
Publication Date:
Grant/Contract Number:
AC05-00OR22725; NA0001982; DESC0005278
Accepted Manuscript
Journal Name:
Journal of Physics. Condensed Matter
Additional Journal Information:
Journal Volume: 28; Journal Issue: 3; Journal ID: ISSN 0953-8984
IOP Publishing
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA); USDOE Advanced Research Projects Agency - Energy (ARPA-E)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1238942