Magnetization Of Pressureless Sintered Fe-B Powders

We report a study about the effects on magnetic properties of pressureless sintering without binder addition performed on iron and boron powder mixture. The obtained self-supported samples appear highly porous or very compact depending on the maximum temperature, T(max), reached during the heating process. They maintain the soft magnetic properties of original Fe-B powder mixture if T(max) does not exceed a critical temperature; afterwards the magnetic properties change very abruptly. A decrease in the magnetization saturation per unit mass, M(s), has been observed to increase the T(max) value. Mossbauer spectroscopy has revealed the presence of Fe2B boride inside the obtained samples whose quantity increases with T(max). Considering the magnetic moment per iron atom in Fe2B as the theoretical one calculated by Ching et al., it has been possible to correlate the T(max) dependence of M(s) with the growing of Fe2B boride. The compacting process seems to be due to the growth of Fe2B boride between Fe/B interfaces.