Thermodynamic properties of samarium and gadolinium polyselenides

• Published in: The Journal of chemical thermodynamics Vol. 90; pp. 122 - 128
• Main Authors: Zelenina, L.N., Chusova, T.P., Vasilyeva, I.G.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2015
• Subjects: Absolute entropy; Enthalpy of formation; Linear phases; Phase diagram; Rare-earth polyselenides; Vapor pressure measurement; Absolute entropy; Linear phases; Rare-earth polyselenides; Vapor pressure measurement; Enthalpy of formation; Phase diagram
• ISSN: 0021-9614; 1096-3626
• DOI: 10.1016/j.jct.2015.06.031

The dependences of Gibbs energy of formation ΔfG298° on the selenium content in LnSex. [Display omitted] •pSe–T–x dependences in LnSe2−δ–LnSe1.5 (Ln=Sm, Gd) were obtained by static method.•The thermodynamic values for dissociation processes were calculated from these data.•The set of standard thermodynamic functions of Sm and Gd polyselenides was obtained.•These set may be used for modeling processes of crystals growth in studied systems. The thermodynamic characteristics (ΔrH298, ΔrS°298) for the stepwise dissociation processes in the systems SmSe1.9–SmSe1.5 and GdSe1.875–GdSe1.5 were calculated from pSe–T–x dependences obtained by the static method with quartz membrane-gauge manometers. Solid phase compositions in the systems studied submit to the same dependence (LnnSe2n−1) which was found by us earlier for the other similar systems. Estimations of entropies and heat capacities of the intermediate polyselenides were carried out by the additive rule with use as reference values of LnSe1.5 thermodynamic characteristics. In this regard, data obtained earlier for the phases GdSex (x=1.85, 1.875) were reprocessed. From the presented information the existence of individual linear phases of polyselenides was proved and a set of standard thermodynamic functions (ΔfH298, S°298, ΔfG°298) were determined for each polyselenide.