“…According to the isothermal section, Cu6(Sn,In)5 can't be in local equilibrium directly with Cu and therefore either Cu3(Sn,In) (or CuIn_Delta) and Cu41Sn11 phases should nucleate between Cu6(Sn,In)5 and Cu. However, as has been previously reported, the solubility and stabilizing effect of In to Cu6(Sn,In)5 is significantly higher than that to Cu3(Sn,In) and Cu41Sn11 [35]. Therefore, even though this interface is not thermodynamically stable, the driving force for nucleation and growth of these additional phases is extremely low.…”