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 x_Ba = 0.03–0.77. Emf measurements were performed at ambient pressure under an inert argon atmosphere using a Ba-Bi(x_Ba = 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 x_Ba = 0.05 and approached unity for mole fractions x_Ba ≥ 0.77. Phase characterization using X-ray diffraction (XRD) was performed on compositions of x_Ba = 0.03–0.77 and thermal characterization was performed on compositions up to x_Ba = 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.