Vapor pressures and thermodynamic properties of strontium silicides

Lattice stability of Ca, Sr and Yb disilicides

“…Experimentally, the CaeSi and the SreSi phase diagrams have been investigated by Manfrinetti et al [12] and Palenzona and Pani [13], their thermodynamic properties of formation at standard pressure and temperature have been derived by Brutti et al [14] and Balducci et al [15] and the high-pressure phase transitions for Ca, Sr and Ba disilicides have been reported by Imai and Kikegawa [16] and Bordet et al [10]. Theoretically, using density functional theory (DFT) within the local density approximation (LDA), various authors have investigated the structure and thermodynamic properties of several AEM silicides [6,17e19].…”

Thermodynamic properties of barium silicides from vapor pressure measurements and density functional calculations

“…However, to the best of our knowledge, no experimental study was published concerning the thermochemical properties of this and other Ba silicides, apart from the early, strongly exothermic heats of formation obtained by Wö hler and Schuff [31] for a couple of compositions by combustion calorimetry. In the case of Sr silicides, these early results were questioned both by the phase diagram assessors [32] and by the present authors, who found much less exothermic values in their KEMS-KEWL study [14]. The only other thermodynamic study previously reported is a calorimetric investigation of the mixing enthalpy in the liquid phase at T ¼ 1723 K [33].…”

“…In view of the NK rule here adopted, this result is not obvious. Indeed the NK rule assumes null formation entropies for all the intermediate phases in the calculation of third-law enthalpy changes: this approximation leads sometimes to serious disagreement between second-and third-law results, as observed by us for example for the Yb-Si and Sr-Si systems [14,41]. The results here obtained for the barium silicides suggest that the formation entropies of these compounds are probably small, therefore only marginally affecting the values of the Gef, or similar for contiguous phases, so leading to a compensation of the inaccuracies in the estimate of the Gef changes for the decomposition reactions.…”

“…KEWL experiments were performed by using a home-modified Ugine-Eyraud vacuum thermobalance coupled with an effusion cell. The experimental assemblies are the same used in our previous works on similar silicide systems [13,14]. The effusion cells employed were machined from molybdenum rods 10 mm in diameter with effusion orifice of 1.0 mm in diameter.…”

“…In two previously published papers, we reported Knudsen Effusion Mass Spectrometry (KEMS) and Knudsen Effusion Weight Loss (KEWL) studies of the Ca-Si [13] and Sr-Si [14] systems, where the complete set of the enthalpies of formation for the intermediate phases was derived from the tensimetric investigation of high temperature decomposition reactions of Ca and Sr silicides. In the latter system, our results were practically first determinations.…”