The heat capacity of natural xenotime-(Y) and synthetic DyPO4 and ErPO4 crystals was determined by differential scanning calorimetry (DSC) attemperatures of 298.15K to 868.15K and a pressure of 0.1 MPa. The aim ofthe study was to develop a method to accurately measure the isobaric heat capacity (CP ) of rare earthelement(REE) phosphates, compare the results to data fromadiabatic calorimetric experiments, and evaluate the deviation from ideality of the CP of the natural xenotime-(Y) solid solution. The measured CP data (in J mol-1 K-1) can be described by the relationships: 185.5 - 751.9T-0.5 - 3.261e + 06 T-2 for DyPO4; 207.2 - 1661T-0.5 - 5.289e + 05 T-2 for ErPO4; and 208 - 1241T-0.5 - 2.493e + 06 T-2 for xenotime-(Y); where T is the temperature in K. The heat capacity data for natural xenotime-(Y) were used to determine the excess function for the solid solution, which yields an excess heat capacity ranging between 7.9 and 10.7%, well within the range of the DSC method used in this study. The experiments indicate that xenotime-(Y) forms a non-ideal solid solution. Future DSC studies will provide important data for developing a solid solution model for the incorporation of REE in xenotime-(Y).
Compounds
#
Formula
Name
1
DyO4P
dysprosium(III) phosphate
2
ErO4P
erbium phosphate
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 heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Small sample (50 mg) DSC
105
POMD
1
Molar heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Small sample (50 mg) DSC
105
POMD
2
Molar heat capacity at constant pressure, J/K/mol ; Crystal
Temperature, K; Crystal
Pressure, kPa; Crystal
Crystal
Small sample (50 mg) DSC
105
POMD
2
Molar heat capacity at constant pressure, J/K/mol ; Crystal