Effects of Ni Substitution in FeSe0.5Te0.5 Superconductor

Ni substitution effects on the Fe 1- x Ni x Se 0.5 Te 0.5 ( x = 0.00, x = 0.05, and x = 0.10) superconductor structure were studied. The polycrystalline samples were synthesized using the solid-state reaction method. The morphology of the samples consists of plate-like crystals with a lamellar structure. X-ray diffraction analyses showed that the samples are described as presenting a PbO-type structure with a tetragonal space group P4/nmm . We analyzed the chemical composition of single crystals using energy-dispersive spectroscopy, and the results showed that there are variations on the chemical composition when the Fe ions are substituted by Ni. Raman spectroscopy on ab- and a(b)c- planes revealed four phonon modes allowed by symmetry. Changes were observed in the spectra with Ni doping. From magnetic measurements of x = 0.00 and x = 0.05 samples, the results showed that the samples are superconductor with a sharp transition in temperatures T C of 14.4 K and 14.6 K, respectively.