Thermodynamic Properties of Si-B Alloys Determined by Solid-State Heterogeneous Phase Equilibrium

To understand the thermodynamic properties of the Si-B binary alloys, experiments were performed to measure the electromotive force (emf) as a function of temperature (823-923 K) using solid-state electrochemical cells that can be represented as (-)Pt,Ar/{Si parallel to CaF2 parallel to {Si-B(alloy)}/Ar, Pt(+) The activities of Si in Si-B alloys were calculated from the experimental emf data obtaining from the solid-state heterogeneous phase equilibrium. The activities of B in Si-B alloys were determined using the Gibbs-Duhem equation. The integralGibbs energy of mixing (Delta G(M)) of alloys were calculated from the partial Gibbs energies of mixing Delta(G) over bar (M) of Si and B and compared with the ideal Gibbs energy of mixing (Delta G(M,ideal)). A significant negative deviation was found for the integral Gibbs energy of mixing (Delta G(M)) of alloys from the ideal Gibbs energy of mixing (Delta G(M,ideal)). The minimum integral molar Gibbs energy of mixing (Delta G(M) = -13.08 kJ/mol) was found at x(B) = 0.8