Alloy phase formation in nanometer-sized particles

Alloy phase formation in nanometer-sized particles has been studied by transmission electron microscopy using particles in the Au–Sn system. When tin atoms are vapor-deposited onto nanometer-sized gold particles, rapid dissolution of tin atoms into gold particles takes place, and as a result, particles of an Au-rich solid solution, of a topologically disordered amorphous-like alloy and of the AuSn compound are formed, depending upon the concentration of tin in a composition range from 0 to 59 at.% Sn. A remarkable enhancement of solubility has been observed in the Au-rich solid solution and the AuSn compound. There is a possibility that the topologically disordered amorphous-like phase, which appears in the middle of a two-phase region (i.e. Au5Sn–AuSn region) of the phase diagram for the bulk alloy, is not a non-equilibrium phase.