Ball milled Mn-doped iron silicide synthesized from Fe-Mn premixture

J. DESIMONI, S. M. COTES, M.A. TAYLOR,J. RUNCO

La Plata, Argentina

Workshop; International Workshop 35th Anniversary of Hyperfine Interactions at La Plata; 2005

The Fe-Si system is complex because, depending on the experimental conditions of synthesis, several stable and metastable phases can be produced. Non-equilibrium processing techniques like mechanical alloying allow the formation of compounds and metastable phases which are not accessible by conventional techniques. In particular, semiconducting b-FeSi2 disilicide have attracted the attention in the last years due to its technological potential in the field of optoelectronic and as a suitable material for thermoelectric conversion [1]. The doping with Mn poses intriguing fundamental issues related to the occurrence of metastable phases arising from the structural differences between iron and manganese silicides and related to the occupancy of the two non-equivalent Fe sites in the b-FeSi2 structure [2], as well.              In the present work,  a study of the sequence of phase formation in powders of stoichiometric Fe1-xMnxSi2 (0.00<x<0.12) mixtures is carried on at room temperature. Samples are prepared by mechanical alloying at room temperature in Ar atmosphere using a horizontal mill. The milling procedure is performed in two steps in order to avoid the formation of Mn silicides. In the first milling step  we produce the Fe-Mn premixture, and in the second step Si is milled together with the Fe-Mn powder.             The sample evolution is followed by means of Mössbauer spectroscopy and X-ray diffraction. Diffractograms are characterized by broad lines, which can be attributed to  stables and metaestables silicides but a contribution from a-Fe(Mn) is also detected. Mössbauer spectra are characterized by two broad central lines and a sexted associated with a-Fe(Mn).   [1] W.-S Cho, S.W. Choi and K. Park, Materials Science and Eng. B66 (199) 116. [2] P. Y. Dusausoy, J. Protas, R. Wandjii and R. Roques, Acta Crystallogr. B27 (1971) 1209.