Thermodynamic Properties of the Intermetallic Systems Lithium‐Antimony and Lithium‐Bismuth

Abstract

Galvanic cells of the type , were employed to determine the Gibbs free energy of formation , and the corresponding enthalpies , and entropies for the systems Li‐Sb and Li‐Bi as a function of composition from pure to the Li‐rich side of the phases. The Li/X ratio was changed systematically by use of the coulometric titration technique. values were obtained by integration of the coulometric titration curve from pure to the composition of interest. Thermodynamic data have been determined for the trilithium compounds as a function of the stoichiometry. and were calculated from the temperature dependence of . Data were obtained over the temperature range 355°–600°C. At 400°C the following values were found for the standard Gibbs free energy of formation: , , , and , all ±0.1 kJ mole−1. The standard enthalpies of formation are: ,, , , all ±0.7 kJ mole−1. The standard entropies of formation are: , , , and, all ±1 J mole−1K−1. The experimental results were also used to examine the phase diagrams for Li‐Sb and Li‐Bi. The range of stoichiometry of is very narrow , whereas exhibits a large deviation from the ideal stoichiometry , predominantly on the lithium‐deficit side. and have been found to be the only intermediate phases existing beside the trilithium phases in the temperature range investigated.