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

Abstract

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 $$ ( - ){\text{Pt}},{\text{Ar}}/\{ {\text{Mg}} + {\text{CaF}}_{2} \cdot{\text{MgF}}_{2} \} \left\| {{\text{CaF}}_{2} } \right\|\{ {\text{Mg}}({\text{alloy}}) + {\text{CaF}}_{2} \cdot{\text{MgF}}_{2} \} /{\text{Ar}}, {\text{Pt}}( + ) $$ 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.