Mossbauer-effect study of the hyperfine field distributions in the residual amorphous phase of Fe-Cu-Nb-Si-B nanocrystalline alloys

Abstract

Amorphous Fq,.5,CUINb3+rSii3.5B9 (x = 0 and 1.5) alloys we% isothermally heat treated at 550' C in a vacuuh for Up to 16 h: 57Fe transmission Massbauer spedra revealed a lower rate of crystallization for x = 1.5. The annealing time dependences of the hyperfine parameters and the different behaviours of the intergranular component in both samples were sNdied via three-dimensional projenions of the hypenine held distributions. Segregation of Fe, Si and also B, from which the crystalline phases have been created, lead to a depletion of these elemene'in the residual amorphous phase. As a consequence, the number of Fe atoms with lib. Cu ' and possibly B atom in their nearest surroundings increased. giving rise to changes in the chemical and topological short-range order. The amount of the residual imorphous phase as well as its average hyperfine field decreased whereas the standard deviation of the hyperfine field dishibution increased with increasing annealing time.

Mössbauer study of FeCoSiAlGaPCB amorphous alloys

“…Figure 6 shows the dependence of average isomer shift, ͗IS͘, at 77 and 300 K as a function of x. A linear increase of ͗IS͘ with x was also found in (FeCo) 80 B 20 12 and (FeCo) 77 B 13 Si 10 17 amorphous alloys. Values of IS are closely related to the s electronic charge densities at the nuclei.…”

“…The high field ͑HF͒ component can be ascribed to sites where Fe atoms are preferentially surrounded by Fe, Co, Si ͑Al,Ga,P͒ and B ͑C͒ atoms and the low field ͑LF͒ one to Fe atoms preferentially surrounded by B ͑C͒ atoms. 20 In order to make easier the discussion of the changes in the HFDs with x, peak position, width, and intensity of the two gaussian components, HF and LF, are plotted in Fig. 8.…”

Crystallization behavior and magnetic properties of Cu-containing Fe–Cr–Mo–Ga–P–C–B alloys

“…2͒ displays a weak tendency to shift to higher field values with decreasing Cr and Mo contents that, as it will be shown below, becomes more pronounced in the case of nanocrystalline alloys. This occurrence seems to indicate that the HF component can be ascribed to sites where Fe atoms are preferentially surrounded by Fe, Ga͑P͒, and B͑C͒ atoms, 7,11 and also by Cr͑Mo͒. The low field ͑LF͒ component can be attributed to Fe atoms preferentially surrounded by B͑C͒ and Cu atoms.…”

Mössbauer Study of Nanocrystalline Alloys

“…M6ssbauer spectroscopy was successfully used for identification of the phases formed due to annealing of the amorphous precursors both of the FeCuNbSiB [20][21][22][23][24][25] and Fe-M-B type alloys [26][27][28][29][30][31][32][33]. However, information regarding the grain size cannot be obtained from the conventional Mössbauer measurements and must be obtained either by the TEM or XRD method.…”

“…The crystallization behaviour of amorphous FeCuNbSiB alloys was studied in great detail [21,[24][25][26]. The analysis of the M6ssbauer spectra allowed the identification of the nanocrystalline phase as the bcc-Fe(Si).…”