Raman and X-ray diffraction studies of superconducting FeTe1-xSex compounds

Iron-based superconducting layered compounds have the second highest transition temperature after cuprate superconductors. Their discovery is a milestone in the history of high-temperature superconductivity and will have profound implications for high-temperature superconducting mechanism as well as industrial applications. We have measured X-ray diffraction and Raman spectra of poly-crystalline FeTe1-xSex samples with x = 0.0, 0.5 and 1 at room temperature. X-ray profile of FeTe and FeTe0.5Se0.5 confirmed the primitive tetragonal unit cell. FeSe is found to be in double phase with tetragonal phase (about 66.62%) and orthorhombic (33.38%). A(1g) and B-1g phonon modes were observed in Raman spectra. At room temperature, these lines are located at 95 and 130 cm(-1) for FeTe, 93 and 129 cm(-1) for FeTe (0.5) Se (0.5) and 93 and 129 cm(-1) for FeSe samples.