Cd-Doped Cu0.5Tl0.5Ba2Ca2Cu3−y Cd y O10−δ (y=0,0.5,1.0,1.5,2.0) Superconductors

Abstract

Superconducting properties of cadmium doped Cu0.5Tl0.5Ba2Ca2Cu3−yCdyO10−δ (y=0,0.5,1.0,1.5,2.0) samples have been studied using X-ray diffraction, resistivity, ac-susceptibility and FTIR absorption measurements. In X-ray diffraction studies these samples have shown to have tetragonal structure. The zero resistivity critical temperature and magnitude of diamagnetism are suppressed with the increased incorporation of Cd in the final compound. A change in the shape of FTIR absorption spectra, after doping, has shown the incorporation of Cd in the unit cell. A systematic hardening of the apical oxygen modes and softening of the CuO2 planar modes of vibration with increased Cd doping have shown that it is incorporated in the unit cell of Cu0.5Tl0.5Ba2Ca2Cu3−yCdyO10−δ (y=0,0.5,1.0,1.5,2.0) superconductors. The FTIR absorption measurements of these samples have shown that hardening of the apical oxygen modes of types Cu(1)–O(2)–Tl and Cu(1)–O(2)–Cu(2)/Cdy (y=0,0.5,1.0,1.5,2.0) increases with the increase of Cd doping in the samples. A softening of the CuO2 planar oxygen mode Cu(2)–O–Cu(2) is also observed with the increased Cd doping in the final compound. It is most likely that hardening of the apical oxygen modes and the softening of the planar modes of vibration are associated damped harmonic oscillations produced by heavier Cd atoms in the CuO2 planes, which suppress the phonon population from a desired level, reducing the magnitude of superconductivity in the final compound.