日本金属学会誌

J. Japan Inst. Metals, Vol. 59, No. 8 (1995),
pp. 769-773

Phase Stability and Transformation in Nanometer-sized Au-Pb Alloy Clusters

Hidehiro Yasuda and Hirotaro Mori

Research Center for Ultra-High Voltage Electron Microscopy, Osaka University, Suita

Abstract:

The structure and phase transformation in nanometer(nm)-sized Au-Pb alloy clusters have been studied in situ by means of transmission electron microscopy (TEM), in order to see the difference of phase equilibrium between a bulk material and the corresponding nm-sized cluster. When lead (or gold) atoms are vapor-deposited onto nm-sized gold (or lead) clusters kept at ambient temperature, spontaneous dissolution of the solute atoms into the clusters takes place and homogeneous Au-Pb alloy clusters are formed. The solid solubilities of lead and of gold in the Au-Pb solid solution clusters remarkably increase as compared to those in the corresponding bulk materials. A stable intermetallic compound formed preferentially in Pb-enriched Pb-Au alloy clusters is AuPb2 with a negative heat of formation. The phase transformation from Au-supersaturated Pb-Au solid solution clusters to single crystalline AuPb2 clusters takes place for a short period, and is similar to ``martensitic'' transformation.


(Received February 15, 1995)

Keywords:

atom cluster, phase transformation, phase stability, spontaneous alloying, transmission electron microscopy, in situ observation


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