Calorimetric and phase diagram studies of the Co–Sn system

Enthalpies of formation of cobalt–tin compounds (βCo3Sn2, CoSn, CoSn2, βCoSn3) have been obtained by direct reaction calorimetry at 1287, 1032, 629 and 604 K, respectively.Integral molar enthalpies of formation of the liquid phase (ΔfHL,T)(ΔfHL,T) have been measured by solution calorimetry at 991 and 1020 K, and by direct reaction calorimetry at 1010 and 1303 K. The experimental (ΔfHL,T)(ΔfHL,T) values in the tin-rich region have been approximated by regular solution model with temperature dependent parameters.The temperature and the enthalpy of the order/disorder transformation αCo3Sn2 → βCo3Sn2 were found to be 833 ± 2 K and 750 ± 30 J/mol, respectively. A metastable phase corresponding to the formula Co2Sn has been observed.The occurrence of the polymorphic transition αCoSn3/βCoSn3 was confirmed although the corresponding transition temperature could not be observed sometimes.