The thermodynamic properties of solid cobalt—tin alloys

Abstract

Reversible potentials of galvanic cells of the form Pt|(CoSn)(alloy)+SnO 2|ZrO 2 + CaO|O 2 (air)|Pt have been measured between 873 and 1323 K. The results have been used to derive the thermodynamic activities and the partial and integral free energies, enthalpies and entropies of formation of the γ, γ′, CoSn and CoSn 2 intermediate phases. Exothermic heats of formation and negative entropies of formation are observed throughout the system. The enthalpies of formation are compared with independent calorimetric and theoretical values and underlying factors influencing their values are considered. The possible contributions to the entropies of formation of the solid phases are discussed and their Debye temperatures are estimated; θ D values of approximately 273, 256 and 169 K are suggested for Co 3Sn 2 (γ), CoSn and CoSn 2, respectively.