Thermodynamic properties of calcium-bismuth alloys determined by emf measurements

Hojong Kim, Dane A. Boysen, David J. Bradwell, Brice Chung, Kai Jiang, Alina A. Tomaszowska, Kangli Wang, Weifeng Wei, Donald R. Sadoway

Research output: Contribution to journalArticle

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Abstract

The thermodynamic properties of Ca-Bi alloys were determined by electromotive force (emf) measurements to assess the suitability of Ca-Bi electrodes for electrochemical energy storage applications. Emf was measured at ambient pressure as a function of temperature between 723 K and 1173 K using a Ca(s)CaF 2(s)Ca(in Bi) cell for twenty different Ca-Bi alloys spanning the entire range of composition from x Ca = 0 to 1. Reported are the temperature-independent partial molar entropy and enthalpy of calcium for each Ca-Bi alloy. Also given are the measured activities of calcium, the excess partial molar Gibbs energy of bismuth estimated from the Gibbs-Duhem equation, and the integral change in Gibbs energy for each Ca-Bi alloy at 873 K, 973 K, and 1073 K. Calcium activities at 973 K were found to be nearly constant at a value of a Ca = 1 × 10 -8 over the composition range x Ca = 0.32-0.56, yielding an emf of ∼0.77 V. Above x Ca = 0.62 and coincident with Ca 5Bi 3 formation, the calcium activity approached unity. The Ca-Bi system was also characterized by differential scanning calorimetry over the entire range of composition. Based upon these data along with the emf measurements, a revised Ca-Bi binary phase diagram is proposed.

Original languageEnglish (US)
Pages (from-to)154-162
Number of pages9
JournalElectrochimica Acta
Volume60
DOIs
StatePublished - Jan 15 2012

All Science Journal Classification (ASJC) codes

  • Chemical Engineering(all)
  • Electrochemistry

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    Kim, H., Boysen, D. A., Bradwell, D. J., Chung, B., Jiang, K., Tomaszowska, A. A., Wang, K., Wei, W., & Sadoway, D. R. (2012). Thermodynamic properties of calcium-bismuth alloys determined by emf measurements. Electrochimica Acta, 60, 154-162. https://doi.org/10.1016/j.electacta.2011.11.023