Thermodynamics Research Center / ThermoML | Journal of Chemical Thermodynamics

The low temperature heat capacity of LaPO4 and GdPO4, the thermodynamic functions of the monazite-type LnPO4 series

Thiriet, C., Konings, R. J. M., Javorsky, P., Magnani, N., Wastin, F.
J. Chem. Thermodyn. 2005, 37, 2, 131-139
ABSTRACT
The heat capacity of lanthanum and gadolinium orthophosphate (LaPO4 and GdPO4) with monazite-like structure (i.e., monoclinic) was measured by hybrid adiabatic relaxation calorimetry in the temperature ranges (2 to 380) K and (0.5 to 301) K respectively. A semi-empirical method has been used to describe the total specific heat as the sum of a lattice and an excess component. An excess contribution due to magnetic effects was observed for GdPO4 below T = 12 K and it was found that GdPO4 orders magnetically below 0.8 K. Combining the results obtained for both compounds, the excess heat capacity for CePO4 was deduced and compared to the excess heat capacity derived from the crystal-field energies. A good agreement has been found between the experimental heat capacity and the calculated one. The thermodynamic functions of the monazite-type LnPO4 series were determined.
Compounds
# Formula Name
1 LaO4P lanthanum orthophosphate
2 GdO4P gadolinium orthophosphate
Datasets
The table above is generated from the ThermoML associated json file (link above). POMD and RXND refer to PureOrMixture and Reaction Datasets. The compound numbers are included in properties, variables, and phases, if specificied; the numbers refer to the table of compounds on the left.
Type Compound-# Property Variable Constraint Phase Method #Points
  • POMD
  • 1
  • Molar entropy, J/K/mol ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • PPMS instrument (Quantum Design)
  • 1
  • POMD
  • 1
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • PPMS instrument (Quantum Design)
  • 318
  • POMD
  • 2
  • Molar entropy, J/K/mol ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • PPMS instrument (Quantum Design)
  • 1
  • POMD
  • 2
  • Molar heat capacity at constant pressure, J/K/mol ; Crystal
  • Temperature, K; Crystal
  • Pressure, kPa; Crystal
  • Crystal
  • PPMS instrument (Quantum Design)
  • 189