A low-temperature calorimetric study of synthetic (forsterite+fayalite) {(Mg2SiO4+Fe2SiO4)} solid solutions: An analysis of vibrational, magnetic, and electronic contributions to the molar heat capacity and entropy of mixing

A calorimetric investigation of spessartine: Vibrational and magnetic heat capacity

“…In this investigation heat-capacity measurements were made between 2 and 865 K on two synthetic spessartine samples using relaxation calorimetry (Lashley et al, 2003;Dachs and Bertoldi, 2005;Dachs and Geiger, 2006;Dachs et al, 2007) and differential scanning calorimetry (DSC) methods (Bosenick et al, 1996). The data allowed a direct determination of the third-law entropy of spessartine garnet for the first time.…”

“…Komada (1986) developed a single-parameter phonon-dispersion model and used it to analyze the low T heat capacity behavior of the iron-silicates deerite and grunerite to obtain their lattice C p (Komada et al, 1995). The KW model was used by Dachs et al (2007) to calculate the lattice heat capacity of Fe-Mg olivine solid solutions. A key feature of the KW model is that, analogous to Debye theory, a characteristic temperature, i.e., h KW , is introduced and the heat capacity is expressed as a function of this single parameter.…”

“…A key feature of the KW model is that, analogous to Debye theory, a characteristic temperature, i.e., h KW , is introduced and the heat capacity is expressed as a function of this single parameter. It can be determined by fitting the model to experimental heat capacity data (Komada, 1986;Komada and Westrum, 1997;Dachs et al, 2007). An attractive feature of this model is the behavior of h KW as a function of temperature, because it allows for an analysis and treatment of magnetic and electronic transitions.…”

“…8). For describing C mag behavior around the sharp k-transition, we used, following Dachs et al (2007), the equations (e.g., Grønvold and Sveen, 1974):…”

Study on Thermodynamic Properties of Fe3+-Substituted Yttrium Iron Garnets

“…In a thermodynamic calculation, C p is necessary to calculate enthalpy and entropy at high temperatures from those at standard state (298.15 K). The vibrational, magnetic and electronic contributions to the molar heat capacity and entropy of Mg 2 SiO 4 + Fe 2 SiO 4 solid solutions have been studied by Dachs and his co-workers [14]. The consequences of oxygen non-stoichiometry and defects on thermodynamic properties in general and Gibbs free energy of formation in particular for three ternary oxide systems, YFeO 3 , YFe 2 O 4 and Y 3 Fe 5 O 12 , have been investigated by Jacob et al [15].…”