Thermodynamic Properties of Dilute Fe-Ge Alloys Studied by the ⁵⁷Fe Mössbauer Spectroscopy

Abstract

The room temperature Mössbauer spectra of 57 Fe were measured for Fe-Ge containing approximately from 1 at.% till 5 at.% germanium. The spectra were analysed in terms of hyperfine parameters of their components related to unlike surroundings of the nuclear probes 57 Fe, determined by different numbers of germanium atoms existing in the neighbourhood of iron atoms. The intensity of the spectrum of components allowed to determine the short-range order, the binding energy E b between two germanium atoms in the studied systems using the extended Hrynkiewicz-Królas idea and the enthalpy of solution HFe−Ge of germanium in iron. It was found that the germanium atoms dissolved in iron matrix interact repulsively and the estimated value of HFe−Ge = −0.88(19) eV/atom. Moreover, the negative values of short-range order parameters α indicate ordering tendencies in annealed samples of Fe-Ge alloys. The results were compared with corresponding values given in the literature which were obtained from calorimetric experiments and the Miedema's model of alloys.