2
0
2017
neu
keg
0
journal
Original
Neumeier, S.[Stefan]
Kegler, P.[Philip]
Arinicheva, Y.[Yulia]
Shelyug, A.[Anna]
Kowalski, P. M.[Piotr M.]
Schreinemachers, C.[Christian]
Navrotsky, A.[Alexandra]
Bosbach, D.[Dirk]
J. Chem. Thermodyn.
2017
2020-09-29
Thermochemistry of La1-xLnxPO4-monazites (Ln = Gd, Eu)
Enthalpy of formation (DH f) of single phase orthophosphate solid solutions La1-xLnxPO4 (Ln = Eu, Gd; 0 less than x less than 1) with monazite structure has been determined by high temperature oxide melt solution calorimetry. The results show a non-ideal behavior of the excess enthalpy of mixing of the solid solutions. This effect is more pronounced for the La1-xGdxPO4 solid solution series and can be attributed to the larger ion size mismatch between La and Gd. The resulting excess enthalpies of mixing given by the Margules interaction parameter of 2.5 +- 2.6 kJ mol-1 and 11.4 +- 3.1 kJ mol-1 for La:Eu and La:Gd cases respectively are in good agreement with data from previous modelling studies. The data are consistent with the formation of thermodynamically stable solid solution in the entire compositional range as is seen by the XRD and Raman measurements. These results are essential for validation of the thermodynamic models that are applied for characterization of the thermodynamic parameters and for the assessment of the long-term stability of monazite solid solution matrices as ceramics for immobilization of radionuclides for nuclear waste disposal.
Enthalpy of mixing
Monazite
Solid solution
High temperature drop solution calorimetry
Thermodynamic modelling
10.1016/j.jct.2016.11.003
105
396-403
1
InChI=1S/Gd
UIWYJDYFSGRHKR-UHFFFAOYSA-N
gadolinium
Gd
2
InChI=1S/P
OAICVXFJPJFONN-UHFFFAOYSA-N
phosphorus
phosphorus-31
red phosphorus
P
3
InChI=1S/O2/c1-2
MYMOFIZGZYHOMD-UHFFFAOYSA-N
oxygen
O2
4
InChI=1S/La
FZLIPJUXYLNCLC-UHFFFAOYSA-N
lanthanum
La
5
InChI=1S/Eu
OGPBJKLSAFTDLK-UHFFFAOYSA-N
europium
Eu
6
InChI=1S/Gd.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+3;/p-3
JAOZQVJVXQKQAD-UHFFFAOYSA-K
gadolinium orthophosphate
GdO4P
1
Synthesized by the authors
1
98
2
Estimated by the compiler
7
InChI=1S/La.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+3;/p-3
LQFNMFDUAPEJRY-UHFFFAOYSA-K
lanthanum orthophosphate
LaO4P
1
Synthesized by the authors
1
98
2
Estimated by the compiler
8
InChI=1S/Eu.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+3;/p-3
KJNZTHUWRRLWOA-UHFFFAOYSA-K
europium phosphate
EuO4P
1
Synthesized by the authors
1
98
2
Estimated by the compiler
1
6
1
Principal objective of the work
AB
TRC
4/21/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
2
Pressure, kPa
Crystal
1
298
3
2
101
3
1
5980
3
1
40
2
7
1
Principal objective of the work
AB
TRC
4/21/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
2
Pressure, kPa
Crystal
1
298
3
2
101
3
1
5060
3
1
30
3
8
1
Principal objective of the work
AB
TRC
4/21/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
2
Pressure, kPa
Crystal
1
298
3
2
101
3
1
5810
3
1
40
4
8
1
7
1
Principal objective of the work
AB
TRC
4/21/2017
1
Excess molar enthalpy (molar enthalpy of mixing), kJ/mol
Calvet calorimetry
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
298
3
2
Pressure, kPa
Crystal
100
1
1
Mole fraction
8
Crystal
1
0.71
2
1
0.2
2
1
1.15
1
0.58
2
1
0.85
2
1
1.36
1
0.34
2
1
0.54
2
1
1.31
1
0.11
2
1
0.98
2
1
1.59
1
0.1
2
1
1.89
3
1
1.79
5
8
1
7
1
Principal objective of the work
AB
TRC
4/21/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
298
3
2
Pressure, kPa
Crystal
101
3
1
Mole fraction
8
Crystal
1
1
3
1
5810
3
1
40
1
0.91
2
1
5730
3
1
30
1
0.82
2
1
5660
3
1
30
1
0.71
2
1
5570
3
1
30
1
0.58
2
1
5470
3
1
30
1
0.4
2
1
5340
3
1
30
1
0.23
2
1
5210
3
1
30
1
0.11
2
1
5130
3
1
30
1
0
3
1
5060
3
1
30
6
6
1
7
1
Principal objective of the work
AB
TRC
4/21/2017
1
Excess molar enthalpy (molar enthalpy of mixing), kJ/mol
Calvet calorimetry
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
298
3
2
Pressure, kPa
Crystal
100
1
1
Mole fraction
6
Crystal
1
0.76
2
1
2.18
3
1
1
1
0.55
2
1
2.95
3
1
1.28
1
0.44
2
1
3.25
3
1
1.16
1
0.24
2
1
1.15
3
1
1.19
7
6
1
7
1
Principal objective of the work
AB
TRC
4/21/2017
1
Mass density, kg/m3
X-ray diffraction
Crystal
Direct value, X
1
Data file compiler
Propagation of evaluated standard uncertainties
95
Crystal
1
Temperature, K
Crystal
298
3
2
Pressure, kPa
Crystal
100
1
1
Mole fraction
6
Crystal
1
1
3
1
5980
3
1
40
1
0.92
2
1
5900
3
1
40
1
0.84
2
1
5820
3
1
40
1
0.76
2
1
5740
3
1
40
1
0.64
2
1
5630
3
1
30
1
0.55
2
1
5540
3
1
30
1
0.44
2
1
5440
3
1
40
1
0.34
2
1
5340
3
1
30
1
0.24
2
1
5260
3
1
30
1
0.11
2
1
5160
3
1
30
1
0
3
1
5060
3
1
30
1
1
-1
Crystal
2
-1
Crystal
6
1
1
Crystal
3
-2
Ideal gas
Principal objective of the work
AB
TRC
4/21/2017
Formation of a compound from elements in their stable state
1
Molar enthalpy of reaction, kJ/mol
Solution calorimetry
298
3
101.325
6
1
Data file compiler
Propagation of evaluated standard uncertainties
95
1
-1959.75
6
1
15.2
2
4
-1
Crystal
2
-1
Crystal
7
1
1
Crystal
3
-2
Ideal gas
Principal objective of the work
AB
TRC
4/21/2017
Formation of a compound from elements in their stable state
1
Molar enthalpy of reaction, kJ/mol
Solution calorimetry
298
3
101.325
6
1
Data file compiler
Propagation of evaluated standard uncertainties
95
1
-1994.36
6
1
15.47
3
5
-1
Crystal
2
-1
Crystal
8
1
1
Crystal
3
-2
Ideal gas
Principal objective of the work
AB
TRC
4/21/2017
Formation of a compound from elements in their stable state
1
Molar enthalpy of reaction, kJ/mol
Solution calorimetry
298
3
101.325
6
1
Data file compiler
Propagation of evaluated standard uncertainties
95
1
-1870.7
6
1
14.51