Thermodynamic properties of platinum-rich intermetallics in the Pt-Gd system

Jacob, K. T. ; Waseda, Y. (1990) Thermodynamic properties of platinum-rich intermetallics in the Pt-Gd system Materials Transactions, JIM, 31 (2). 135-140 . ISSN 0916-1821

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Phase relations in the Pt-GdPt portion of the system have been determined at 1100 K by X-ray and microscopic examination of quenched samples equilibrated for 610 ks. Five compounds have been identified; GdPt5, `GdPt3', GdPt2, Gd3Pt4 and GdPt. The phase GdPt3 with AuCu3 type structure has not been reported earlier. The compound GdPt3 is nonstoichiometric with a homogeneity range extending from 23 to 28 mol% Gd. The phase GdPt2 has a narrower nonstoichiometric range varying from 32 to 33 mol% Gd. The relative partial Gibbs' energy of Gd in the two-phase fields has been determined in the temperature range 925-1125 K using solid state galvanic cells incorporating single crystal CaF2 as the solid electrolyte and an equimolar mixture of Gd + GdF3 as the reference electrode. The Gibbs' energy formation of the intermetallic phases per mol has been derived from these measurements: Gd0.17Pt0.83:ΔGM = -60650+1.30 T(±80) J/mol Gd0.23Pt0.77:ΔGM = -78220+1.81 T(±180) J/mol Gd0.28Pt0.72:ΔGM = -91686+2.077 T(±290) J/mol Gd0.32Pt0.68:ΔGM = -94750-2.53 T(±300) J/mol Gd0.33Pt0.67:ΔGM = -96135-2.11 T(±310) J/mol Gd0.43Pt0.57:ΔGM = -103575-1.31 T(±360) J/mol Gd0.50Pt0.50:ΔGM = -104000+0.80 T(±380) J/mol

Item Type:Article
Source:Copyright of this article belongs to The Japan Institute of Metals.
Keywords:Free Energy; Enthalpy; Entropy of Mixing:Solid State Cell; Emf; Phase Relations; Structure
ID Code:94862
Deposited On:05 Oct 2012 09:09
Last Modified:05 Oct 2012 09:09

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