EXAFS Studies of Glassy Ni₆₆B₃₃: A Multi-Shell Modeling of the Ni-Ni Distribution

Abstract

The formation of transition metal-metalloid (TM_100−xM_x) glassy alloys by rapid quenching from the melt is usually confined to a limited composition range of about 15≤x≤25 at .%. However, glassy alloys of the type TM-M substantially removed from the 80:20 atomic ratio have been prepared. Takaheshi et al. [1] have found noncrystalline X-ray diffraction patterns in Ni-R samples at 18.5 and at 40 at .% B. Inoue et al. [2] have reported on metallic glasses in the Ni-B and Co-B systems containing 33–43 at .% B and 35–41 at .% B, respectively. More interestingly, amorphous Ni₆₆B₃₃ crystallized homogenously to a single Ni₂B phase of known crystal structure (that of Al₂Cu), in which there is only one nonequivalent Ni site [3]. The existence of the Ni₆₆B₃₃ composition in both the crystalline and glassy phases makes it an attractive model system for quantitative EXAFS investigation of the local atomic environment in metal-metalloid glasses.