Thermodynamic Properties of Magnesium-Boron Binary Alloys Determined Using Solid-State Electrochemical Measurements

This study provides the thermodynamic properties of the Mg-B binary alloys. Experiments were performed to measure the electromotive force (emf) as a function of temperature (773 K to 873 K) using a solid-state electrochemical cells that can be represented as $$(-)\text{Pt},\text{Ar}/\{\text{Mg}+{\text{CaF}}_2\cdot {\text{MgF}}_2\}\parallel {\text{CaF}}_2\parallel \left\{\text{Mg}\right(\text{alloy})+{\text{CaF}}_2\cdot {\text{MgF}}_2\}/\text{Ar},\text{Pt}(+)$$The activities of Mg in Mg-B alloys were calculated from the experimental emf data. The activity coefficients of Mg in Mg-B alloys were also determined. The integral Gibbs energies of formation (∆G_f^°) of alloys were calculated from the activities of the Mg using tangent rule. The integral Gibbs energies of formation (∆G_f^°) of MgB₂, MgB₄, and MgB₇ are − 15.48, − 22.03, and − 15.89 kJ/mol-atoms at 873 K.