Structure characterization of amorphous alloys by T-O-F pulsed neutron scattering using accelerator neutron sources

This paper reviews the experimental characterization of local atomic environment in amorphous solid alloys, carried out by time-of-flight pulsed neutron total scattering technique using the epithermal short-wavelength neutrons generated in electron and proton accelerators. Available accelerators are a 300 MeV electron LINAC at the Tohoku University and a 500 MeV proton booster synchrotron in National Laboratory for High Energy Physics in Japan. The obtained spectra of pulsed neutrons show strong enhancement of the epithermal region, and this epithermal neutrons are the powerful probe for the high resolution observation of the short-range structure. The palladium-germanium amorphous alloy system is a good candidate to examine the short-range structure. Hayashi et al. have measured the compositional dependence of the short-range structure of Pd-Ge amorphous alloys, and concluded that the chemical short-range structure between Pd and Ge atoms must be characterized by a trigonal prismatic configuration analogous to that found in Pd3Si. A high epithermal neutron flux is useful to supply the structural information of natural boron-containing amorphous alloys. The chemical short-range structure in Ni-74 at. percent Ti amorphous alloy was found to be quite analogous to that in NiTi2 crystal structure. However, some difference of the chemical short-range order between Ni-Ti and Cu-Ti amorphous alloys was observed. The anisotropic factor of Mo-32 at. percent Si amorphous alloy was also measured. The local environment around hydrogen atoms in amorphous alloys was studied. (Kato, T.)