Structural Study of Pd-Based Amorphous Alloys with Wide Supercooled Liquid Region by Anomalous X-ray Scattering

Abstract

The anomalous X-ray scattering (AXS) measurements have been made to determine the local ordering structures around Ni and Cu in Pd 40 Ni 10 Cu 30 P 20 and Pd 40 Ni 40 P 20 alloys in both the liquid and amorphous state using the synchrotron radiation at incident X-ray energies close to the K-absorption edges of Ni and Cu. A characteristic small hump was clearly found at r=0.37 nm in the environmental radial distribution function (RDF) around Cu in liquid and amorphous Pd 40 Ni 10 Cu 30 P 20 alloy. Such peak was not detected in the environmental RDF around Ni, and the local atomic arrangement around Ni was found to be similar to the Pd 40 Ni 40 P 20 case. These experimental facts can be described when considering the trigonal prismatic packing related to Ni and the tetragonal dodecahedral packing related to Cu. This is in a sense a necessary condition at best, although it might not be the sufficient condition. However, the effect of elemental substitution with Cu for Ni in the Pd-Ni-Cu-P alloy is thought to induce the particular atomic association related to Cu, which is an important factor for exhibiting its wide supercooled liquid region and high reduced glass transition temperature.