Thermodynamic properties of strontium-lead alloys determined by electromotive force measurements

The thermodynamic properties of Sr-Pb alloys were determined by electromotive force (emf) measurements. A Sr(s)|CaF₂-SrF₂|Sr(in Pb) electrochemical cell was used to measure emf values at 773–1073 K for Sr-Pb alloys at mole fractions xSr = 0.07–0.59. These emf measurements were used to determine thermodynamic properties of Sr-Pb alloys, including activity, partial molar entropy, and partial molar enthalpy. At 873 K, activity values of Sr in Pb were as low as aSr = 1.72 × 10^–9 at mole fraction xSr = 0.07, implying strong atomic interactions between Sr and Pb. Phase transition temperatures of Sr-Pb alloys, observed during emf measurements, were corroborated by thermal analysis (0.07 ≤ xSr ≤ 0.34) by differential scanning calorimetry (DSC), and the phase constituents of Sr-Pb alloys (0.07 ≤ xSr ≤ 0.75) were characterized using X-ray diffraction (XRD). Experimentally-determined thermodynamic properties were compared to the assessed thermodynamic properties of the Sr-Pb system, confirming the phase transition temperatures and highlighting discrepancies in solution properties (activity and excess Gibbs energy).