Compositional partition in Ag-Nb alloy clusters produced by a plasma-gas-condensation cluster source

We have produced Ag-Nb clusters by a facing-target type plasma-gas-condensa tion cluster source as our first step toward alloy cluster formation. The A g-Nb clusters have been deposited on substrates and examined by a transmiss ion electron microscope with a nano-beam energy dispersive X-ray analysis. We have obtained Ag-Nb alloy clusters with the sizes range between 5 and 10 nm in diameter. Their chemical compositions are broadly dispersed and part itioned into Ag-rich and Nb-rich ones, being consistent with the immiscible type equilibrium phase diagram. This result suggests that alloy cluster fo rmation is driven by the alloy phase stability. (C) 2000 Acta Metallurgica Inc.