Crystal structure and Raman scattering characterization of Cu2Fe1- xCoxSnS4 chalcogenide compounds

Abstract

This work reports the synthesis by solidestate reaction of Cu2Fe1-xCoxSnS4 solid solutions. Crystal structures of Cu2Fe0.8Co0.2SnS4 and Cu2Fe0.6Co0.4SnS4 were investigated by single crystal X-ray diffraction. Both phases crystallize in the tetragonal stannite-type structure. The volume of the tetrahedral [MS4] (M¼ Fe, Co) presented the highest distortion, with Edge-Length Distortion (ELD) indices ~2% from the ideal tetrahedron. The powder X-ray diffraction (XRD) patterns of Cu2Fe1-xCoxSnS4 (x ¼ 0.2, 0.4, 0.6 and 0.8) has been refined by Rietveld method. No secondary phases were detected in XRD patterns. An analysis of the vibrational properties of Cu2Fe1-xCoxSnS4 was performed using Raman scattering measurements. The Raman peaks were analyzed by fitting of the spectra and subsequently identifying the vibrational modes by comparison with experimental and theoretical data from Cu2FeSnS4 (CFTS) and Cu2CoSnS4 (CCTS) end-members. The spectra from Cu2Fe1-xCoxSnS4 show that there is a variation in the frequency of the main A1 peak at ~320 cm 1 together with a decrease in the secondary mode intensity at ~285 cm 1. Full Width at Half Maximum (FWHM) and the intensity of the Raman peaks reflect the high crystallinity of Cu2Fe1-xCoxSnS4 solid solutions. The oxidation states of the metals were confirmed by temperature-dependent magnetization measurements performed in the antiferromagnetic Cu2Fe1- xCoxSnS4 solid solutions