Yoshihiro Takahara and Nobutaka Narita
Department of Materials Science and Engineering, Faculty of Engineering, Kyushu Institute of Technology, Kitakyushu 804-8550Local atomic structures of an amorphous Fe79B16Si5 alloy before and after structural relaxation have been studied by EXAFS (extended X-ray absorption fine structure) and Mössbauer measurements.
The structural analyses indicate that the interatomic distance of Fe-Si is larger than that of Fe-B and is close to the Fe-Fe distance. Such geometry becomes more obvious by structural relaxation. Discussions based on the medium range order model of capped trigonal prisms suggest that Si atoms do not occupy the center of the capped trigonal prisms as metalloid atoms. It is likely to locate the substitutional sites of Fe atoms. During structural relaxation, the distance of Fe-B decreases and that of Fe-Fe is slightly shortened, while the Fe-Si distance remains unchanged. The coordination number of B atoms around Fe decreases but that of Fe atoms increases a little. The coordination number of Si around Fe is almost constant. The coordination number increase of Fe around Fe during the structural relaxation is also confirmed in the Mössbauer spectra.
local atomic structure, extended X-ray absorption fine structure, Mössbauer effect, capped trigonal prism, medium range order structure, iron-boron-silicon alloy