Mossbauer and Electrochemical Investigations of Carbon-Rich Fe1-xCx Films

A thin film binary library of carbon-rich Fe1-xCx (0.47 < x < 0.97) alloys was prepared by combinatorial sputtering of carbon and iron. The sputtered library was characterized by X-ray diffraction and room temperature Fe-57 Mossbauer effect spectroscopy to determine its microstructure. X-ray diffraction results show that the Fe1-xCx film is amorphous in the whole composition range of the library. For 0.52 <= x <= 0.59, a hyperfine field distribution and a quadrupole splitting distribution as obtained from Mossbauer spectra indicate the presence of a ferromagnetic phase and a paramagnetic phase in this regime. With increasing of carbon content, for 0.61 <= x <= 0.97, the sextet disappears and two paramagnetic doublets splitting appear suggesting two different Fe sites. The electrochemical performance of the Fe1-xCx film was investigated in lithium cells and the presence of Fe was found to increase the reversible capacity per mass of carbon over that of a pure carbon electrode. (C) 2015 Elsevier Ltd. All rights reserved.