Structural and thermodynamic mixing properties of La1−xNdxPO4 monazite-type solid solutions

H. Schlenz, J. Dellen, P. Kegler, C. Gatzen, C. Schreinemachers, A. Shelyug, M. Klinkenberg, A. Navrotsky, D. Bosbach

Research output: Contribution to journalArticlepeer-review

Abstract

La1−xNdxPO4 monazite-type ceramics were synthesized by precipitation and sintering. The obtained crystalline powders and pellets were structurally characterized by X-ray diffraction, electron microscopy, and infrared and Raman spectroscopy. The determined unit cell constants agree with published values for the pure end-members ranging from LaPO4 to DyPO4, as well as with values for known mixed monazite-type lanthanide orthophosphates, indicating a homogeneous solid solution. However, Raman spectroscopy shows a change in short-range order and the results of high temperature oxide melt solution calorimetry suggest a subregular solid solution, which requires two Margules parameters to calculate the observed enthalpy of mixing ΔHmix for La1−xNdxPO4, which is positive and asymmetric and shows a maximum at x = 0.299 (ΔHmix=7.53±0.01kJmol−1) at 298 K.

Original languageEnglish (US)
Pages (from-to)470-478
Number of pages9
JournalJournal of Solid State Chemistry
Volume270
DOIs
StatePublished - Feb 2019

Keywords

  • Actinides
  • Crystal structure
  • Enthalpy of mixing
  • Monazite
  • Nuclear waste
  • Solid solution

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

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