TY - JOUR
T1 - Thermochemistry of the alkali rare-earth double phosphates, A3RE(PO4)2
AU - Ushakov, Sergey V.
AU - Navrotsky, Alexandra
AU - Farmer, J. Matt
AU - Boatner, Lynn A.
N1 - Funding Information:
This work was supported by the United States Department of Energy (grant FG03-97ER45654). Work at ORNL was supported by the Office of Basic Energy Sciences, U.S. DOE. Oak Ridge National Laboratory is managed by UT-Battelle, LLC, for the U.S. Department of Energy under contract DE-AC05-00OR22725. The authors thank Dr. Juraj Majzlan for editing the manuscript and Dr. Sergey Krivovichev for discussion.
PY - 2004/7
Y1 - 2004/7
N2 - 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.
AB - 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.
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U2 - 10.1557/JMR.2004.0283
DO - 10.1557/JMR.2004.0283
M3 - Article
AN - SCOPUS:4143152835
SN - 0884-2914
VL - 19
SP - 2165
EP - 2175
JO - Journal of Materials Research
JF - Journal of Materials Research
IS - 7
ER -