EXAFS Spectroscopy with Amorphous Transition Metal-Metalloid Alloys

Abstract

Abstract EXAFS measurements were performed with amorphous T80M20 (T=Fe,Co, Ni; M=B,P). For the interpretation of the EXAFS spectra it was necessary also to compare them with spectra obtained from crystalline specimes with known atomic arrangement and with similar chemical composition such as the alloys Fe2B, CO3B, Ni3B as well as Fe3P, CO3P, and Ni3P. As a radiation source the Ag-target of a rotating anode X-ray generator (6 kW) was used. The spectra were obtained using a flat LiF-(220) monochromator. The specimens were kept at 80 K and thus thermal effects could be reduced. The EXAFS spectra of the amorphous alloys and those of the corresponding crystalline compounds of the type T3M show among each other a relatively great similarity. The greatest similarity exists in the case of the Ni-and Co-alloys. The amorphous alloys based on iron however show larger discrepancies with respect to the corresponding crystalline ones, where the greatest deviation occurs with the compound Fe2B. The Fourier transforms show such similarities too. The EXAFS spectra of the crystalline elements Fe. Co, and Ni as well as their Fourier transforms evidently show differences compared to the amorphous specimens and to the T3M compounds. The similarities observed between the amorphous alloys and the corresponding crystalline specimens of the T3M-type together with their large discrepancies with respect to the pure metals led to the conclusion that the local structure in the amorphous alloys is in considerable accordance with that of the corresponding T3M-compound.