Thermodynamic properties of a quasi-ionic alloy from electromotive force measurements: The Li–Pb system

Abstract

Electromotive force measurements of the activity of lithium in lithium–lead liquid alloys are reported in the temperature range T=770–932 K. The partial molar excess Gibbs free energies are negative. Variations with composition exhibit an inflection point around an atomic fraction of lead equal to 0.2 which corresponds to the ratio of the valences of Li and Pb. The inflection point, as well as structural data, may be interpreted by assuming an at least partly ionic character of the alloy. A set of partial structure factors defined by Faber and Ziman are calculated as a function of the composition at the long‐wavelength limit. Their variations support the hypothesis of a local short‐range order around the above‐mentioned composition (0.2). Finally, a modeling approach based on an electron transfer from Li to Pb is used to explain some of the characteristics of this class of alloys.