Thermodynamic properties of Sr-Sn alloys via emf measurements and thermal analysis

The thermochemical properties of Sr-Sn alloys were determined by electromotive force (emf) measurements to evaluate liquid tin as an interacting electrode material for separating alkaline-earth elements from molten salt solutions. A Sr(s)|CaF2-SrF2|Sr(in Sn) cell was used to measure emf values for twelve Sr-Sn alloys at mole fractions xSr = 0.02‒0.43, allowing the determination of thermochemical properties such as activity and partial molar quantities of Gibbs energy, entropy, and enthalpy of Sr at 730‒1110 K. Activity values of Sr in liquid Sn were as low as 6.9×10‒12 at 800 K and xSr = 0.02 indicating highly non-ideal solution behavior between Sr and Sn. Phase transitions were also determined from the emf data and were validated via differential scanning calorimetry (DSC). Through the combination of emf measurements for thermochemical properties, X-ray diffraction (XRD) for phase constituents, and DSC measurements for phase transitions, this work established more complete thermodynamic properties of the Sr-Sn binary system.