TY - JOUR
T1 - Heat capacities and thermodynamics of formation of ε-Keggin MAl12 Selenates (M = Al(III), Ga(III), or Ge(IV))
AU - Reusser, Dana
AU - Schliesser, Jacob
AU - Woodfield, Brian F.
AU - Navrotsky, Alexandra
N1 - Funding Information:
We would like to thank Dr. Kristina Lilova and Dr. Jianqi Qi for their work on the enthalpies of drop solution for α-Al 2 O 3 . Support for the experimental thermochemical research (synthesis, characterization, heat of formation measurements and D.R. salary) at UC Davis was provided by the U.S. Department of Energy Office of Basic Energy Sciences via Grant DE-FG02-97ER14749 . Support for heat capacity measurements at BYU was provided by the U.S. Department of Energy under Grant DE-FG02-05ER15666 . The samples were prepared in the laboratory of W.H. Casey and we thank him for his guidance and use of materials and facilities for their preparation. That work was supported by the U.S. Department of Energy Office of Basic Energy Science Grant DE-FG02-05ER15693 .
Publisher Copyright:
© 2015 Elsevier Ltd.
PY - 2015/6/25
Y1 - 2015/6/25
N2 - Abstract We report enthalpies of formation from the elements and oxides, ΔfH° = -(22,673.44 ± 30.19) kJ·mol-1 and Δf,oxH = -(869.68 ± 28.75) kJ·mol-1, for [GeO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (GeAl12) measured using high temperature oxide-melt solution calorimetry. This material is the selenate salt of the germanium-substituted polynuclear Al137+ ion in the ε-Keggin structure. We also report heat capacities from temperatures of (2 to 300) K on this GeAl12 selenate and its other heterometal substituted forms, Na[AlO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (AlAl12) and Na[GaO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (GaAl12), measured using a Quantum Design Physical Property Measurement System (PPMS). These measurements were used to calculate entropies and subsequently free energies of formation for these three materials. All three MAl12 selenates, where M = Al(III), Ga(III), or Ge(IV), have similar heat capacities from temperatures (2 to 300) K and similar characteristic Debye temperatures, ΘD, suggesting similar lattice vibrational densities of states.
AB - Abstract We report enthalpies of formation from the elements and oxides, ΔfH° = -(22,673.44 ± 30.19) kJ·mol-1 and Δf,oxH = -(869.68 ± 28.75) kJ·mol-1, for [GeO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (GeAl12) measured using high temperature oxide-melt solution calorimetry. This material is the selenate salt of the germanium-substituted polynuclear Al137+ ion in the ε-Keggin structure. We also report heat capacities from temperatures of (2 to 300) K on this GeAl12 selenate and its other heterometal substituted forms, Na[AlO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (AlAl12) and Na[GaO4Al12(OH)24(H2O)12](SeO4)4·12H2O(cr) (GaAl12), measured using a Quantum Design Physical Property Measurement System (PPMS). These measurements were used to calculate entropies and subsequently free energies of formation for these three materials. All three MAl12 selenates, where M = Al(III), Ga(III), or Ge(IV), have similar heat capacities from temperatures (2 to 300) K and similar characteristic Debye temperatures, ΘD, suggesting similar lattice vibrational densities of states.
KW - Al
KW - Enthalpy of formation
KW - Heat capacity
KW - Keggin
KW - Polyoxocation
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U2 - 10.1016/j.jct.2015.06.001
DO - 10.1016/j.jct.2015.06.001
M3 - Article
AN - SCOPUS:84934975802
SN - 0021-9614
VL - 89
SP - 296
EP - 305
JO - Journal of Chemical Thermodynamics
JF - Journal of Chemical Thermodynamics
M1 - 4260
ER -