Effects of third elements, B, Si and Al, on the atomic structure of the NiZr 2 amorphous alloy

Abstract

X-ray diffraction and mass density measurements for the (NiZr 2) 1− x M x (M = B, Si and Al) amorphous alloys have been carried out in order to elucidate the effects of the addition of the third element M on the structure of the parent amorphous matrix NiZr 2. The radial distribution function G( r) and the mass density of the amorphous (NiZr 2) 1− x B x ( x = 0–0.15) remain unchanged in spite of an increase in B concentration. In the amorphous (NiZr 2) 0.8Si 0.2, however, the first peak in G( r) is found to grow substantially relative to the second peak. This is interpreted as the growth of the ZrSi correlation at the distance close to the original NiZr correlation. In contrast, the intensities in G( r) associated with both NiAl and ZrAl correlations in the amorphous alloys (NiZr 2) 1− x Al x ( x = 0–0.3) increase equally and the density decreases linearly with increasing Al concentration in the manner consistent with those expected from a random substitution. From the present structural studies coupled with the previous results on the electronic structure, we conclude that there exist preferential bondings of Si and B atoms with the host Zr atoms and that Al atoms are substituted randomly for Ni or Zr without any preference.