Thermochemistry of the alkali rare-earth double phosphates, A3RE(PO4)2

Sergey V. Ushakov, Alexandra Navrotsky, J. Matt Farmer, Lynn A. Boatner

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


The formation enthalpies for alkali rare-earth compounds of the type K3RE(PO4)2 where RE = Sc, Y, Lu, Er, Ho, Dy, Gd, Nd, or Ce and for A3Lu(PO4 2 compounds with A = K, Rb, or Cs were determined using high-temperature oxide-melt solution calorimetry. Structural phase transitions were observed and characterized using differential scanning calorimetry and high-temperature x-ray diffraction. The formation enthalpy of the K3RE(PO4)2 phases from oxides becomes more exothermic with increasing rare-earth radius for the K3RE(PO4)2 series and with increasing alkali radius for the A3Lu(PO4)2 compounds. The K3RE(PO4)2 phases are stable with respect to anhydrous K3PO4 and REPO4. The monoclinic K3RE(PO4 2 compounds undergo a reversible phase transition to a hexagonal (glaserite-type) structure with a phase transition temperature that increases from -99 to 1197 °C with increasing RE ionic radius going from Lu to Ce.

Original languageEnglish (US)
Pages (from-to)2165-2175
Number of pages11
JournalJournal of Materials Research
Issue number7
StatePublished - Jul 2004
Externally publishedYes

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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