Effect of CuO2 planes on the structural and superconducting transport properties of [CuTl − 12(n − 1)n;n = 2,3,4] superconductor family

Abstract

Cu 0.5 Tl 0.5 Ba 2 Ca n−1 CunO 2n+4−δ (n = 2, 3, 4) superconducting bulk samples have been synthesized by using two-step solid state reaction method. We investigated the effects of CuO 2 planes on the structural and superconducting transport properties of [CuTl-12(n−1)n; n = 2, 3, 4] superconducting family. These samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) absorption spectroscopy and DC-resistivity (ρ) measurements. These samples are c-axis length oriented and have shown orthorhombic crystal structure. All the samples have shown metallic variations of resistivity from room temperature down to onset of superconductivity. The zero resistivity critical temperature Tc(R = 0) increases with the increase in superconducting planes and normal state resistivity systematically decreases, which show the density of inadvertent defects decreases in the final compound. The apical oxygen phonon modes are hardened as observed in the FTIR absorption measurements. The intrinsic microscopic superconducting parameters, such as the cross-over temperatures, coherence length along c-axis (ξ c(0) ) at 0 K, inter-layer coupling (J), inter-grain coupling (α) and fermi velocity (V F ), were extracted from the fluctuation-induced conductivity (FIC) analysis. FIC analysis also showed the improvement in superconductivity with the increase in CuO 2 planes.