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Thermodynamic properties of Pt5La, Pt5Ce, Pt5Pr, Pt5Tb and Pt5Tm intermetallics

Jacob, KT and Waseda, Y (1990) Thermodynamic properties of Pt5La, Pt5Ce, Pt5Pr, Pt5Tb and Pt5Tm intermetallics. In: Bulletin of Materials Science, 13 (4). pp. 235-244.

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Abstract

The Gibbs’ energies of formation of Pt5La, Pt5Ce, Pt5Pr, Pt5Tb and Pt5 Tm intermetallic compounds have been determined in the temperature range 870–1100 K using the solid state cell:Ta,M + MF3 /CaF2 /Pt5 M + Pt + MF3 ,TaTaM+MF3CaF2Pt5M+Pt+MF3Ta.The reversible emf of the cell is directly related to the Gibbs’ energy of formation of the Pt5M compound. The results can be summarized by the equations:DGf° á Pt5 La ñ = - 373,150 + 6 ·60 T( ±300 )J mol - 1 DGf° á Pt5 Ce ñ = - 367,070 + 5 ·79 T( ±300 )J mol - 1 DGf° á Pt5 Pr ñ = - 370,540 + 4 ·69 T( ±300 )J mol - 1 DGf° á Pt5 Tb ñ = - 372,280 + 4 ·11 T( ±300 )J mol - 1 DGf° á Pt5 Tm ñ = - 368,230 + 4 ·89 T( ±300 )J mol - 1 Unknown control sequence '\hfill'relative to the low temperature allotropic form of the lanthanide element and solid platinum as standard states The enthalpies of formation of all the Pt5M intermetallic compounds obtained in this study are in good agreement with Miedema’s model. The experimental values are more negative than those calculated using the model. The variation of the thermodynamic properties of Pt5M compounds with atomic number of the lanthanide element is discussed in relation to valence state and molar volume.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Indian Academy of Sciences.
Keywords: Platinum;lanthanide intermetallic compounds;Gibbs’ energy of formation;enthalpy of formation;entropy of formation; systematics
Department/Centre: Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited: 09 Dec 2011 10:27
Last Modified: 09 Dec 2011 10:27
URI: http://eprints.iisc.ernet.in/id/eprint/42664

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