Low-temperature synthesis of micro- and nano-crystalline CuFeS 2 polymorphs

Micro- and nano-crystalline polymorphs of CuFeS2 have been synthesized by using simple, low temperature solvothermal and precipitation methods. A solvothermal process at 170 °C, using ethylenediamine produced micro- and nano-crystalline CuFeS2 with various shapes and morphologies, which include polygons, pyramids, hexagonal rods and plates etc. In addition to the expected tetragonal, chalcopyrite phase, a new, relatively low symmetry, hexagonal, wurtzite phase of CuFeS2 was also obtained. The wurtzite phase fraction was found to be ~21 wt% by Rietveld analysis using X-ray powder diffraction data. Further, the effects of solvent concentration, reaction temperature and annealing on the crystallites have been studied. By the solvothermal process carried out at 140 °C, hexagonal, wurtzite phase CuFeS2 was obtained with a phase fraction as high as ~92 wt%. A relatively, simple and low-temperature precipitation process using (NH4)2S and distilled water produced micro- and nano-crystalline CuFeS2 with various shapes including rods, hexagonal plates, and spheres etc. The synthesis methods reported here are believed to be beneficial for the further development of CuFeS2 in the field of nanotechnology.