Thermodynamic Properties of Barium-Antimony Alloys Determined by Emf Measurements

The thermodynamic properties of Ba-Sb alloys, including the activity, partial molar entropy, and partial molar enthalpy, were determined using the electromotive force (emf) technique for thirteen compositions spanning the composition range of xBa = 0.03-0.77. Emf measurements were performed at ambient pressure under an inert argon atmosphere using a Ba-Bi(xBa = 0.05)|CaF2-BaF2|Ba(in Sb) electrochemical cell at 723-1073 K. At 923 K, activity values of Ba in Sb were as low as 2.0 × 10−15 at mole fraction xBa = 0.05 and approached unity for mole fractions xBa ≥ 0.77. Phase characterization using X-ray diffraction (XRD) was performed on compositions of xBa = 0.03-0.77 and thermal characterization was performed on compositions up to xBa = 0.40 using differential scanning calorimetry (DSC). Integrating the results from emf, XRD, and DSC measurements, an experimentally determined Ba-Sb phase diagram was constructed.