• Thermodynamic properties of Pt5La, Pt5Ce, Pt5Pr, Pt5Tb and Pt5 Tm intermetallics

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    • Keywords

       

      Platinum-lanthanide intermetallic compounds; Gibbs’ energy of formation; enthalpy of formation; entropy of formation; systematics

    • 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:$$Ta,M + MF_3 /CaF_2 /Pt_5 M + Pt + MF_3 ,Ta$$.

      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:$$\begin{gathered} \Delta G_f^ \circ \left\langle {Pt_5 La} \right\rangle = - 373,150 + 6 \cdot 60 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Ce} \right\rangle = - 367,070 + 5 \cdot 79 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Pr} \right\rangle = - 370,540 + 4 \cdot 69 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tb} \right\rangle = - 372,280 + 4 \cdot 11 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \Delta G_f^ \circ \left\langle {Pt_5 Tm} \right\rangle = - 368,230 + 4 \cdot 89 T\left( { \pm 300} \right)J mol^{ - 1} \hfill \\ \end{gathered} $$ 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.

    • Author Affiliations

       

      K T Jacob1 Y Waseda2

      1. Department of Metallurgy, Indian Institute of Science, C V Raman Avenue, Bangalore - 560 012, India
      2. Institute of Mineral Dressing and Metallurgy (SENKEN), Tohoku University, Sendai - 980, Japan
    • Dates

       
  • Bulletin of Materials Science | News

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