Alloy Phase Formation in Isolated Nanometer-sized Particles in the Sn-Pb System

摘要

Alloy phase formation in nanometer-sized particles has been studied by in situ transmission electron microscopy using particles in the Sn-Pb system. In approximately 15-nm-sized alloy particles kept at 130°C, the formation of a liquid phase which is not an equilibrium phase in bulk at 130°C, was confirmed. At room temperature, however, these particles with compositions near the eutectic composition exhibited a mixture of two crystalline phases. On the other hand, in an approximately 5-nm-sized alloy particle, a direct phase change from crystalline to liquid has taken place by alloying tin atoms into lead particles even at room temperature. In view of the fact that the eutectic temperature of bulk alloys is 183°C, it seems safe to consider that suppression of the eutectic temperature as much as 50°C and 160°C took place in association with decreasing size of particles down to 15 nm and 5 nm in diameter, respectively.