SUPERCONDUCTIVITY AND TRANSPORT CRITICAL CURRENT DENSITY IN Tl1-xPbxSr1.8Sb0.2CaCu2O7 CERAMICS

Abstract

Superconducting properties of Tl_1-xPb_xSr_1.8Sb_0.2CaCu₂O₇ (x = 0.1 – 0.6) ceramics prepared using solid-state synthesis have been investigated. Tl_1-xPb_xSr_1.8Sb_0.2CaCu₂O₇ (x = 0.1 – 0.5) showed metallic normal state behavior and an increase in T_{c zero} from 26 K at x = 0.1 to a maximum value of 80 K at x = 0.5. Further substitution of Pb to x = 0.6 caused a decrease in T_{c zero} to 27 K. The transport critical current density, J_c measured in zero magnetic field for Tl_1-xPb_xSr_1.8Sb_0.2CaCu₂O₇ (x = 0.1 – 0.4) between 20 K and 80 K was determined by the four-point probe measurement using the 1µVcm^-1 criterion. J_c increases when the temperature is reduced for all samples (x = 0.2 – 0.4). The results of the electrical measurements and powder X-ray diffractions analysis are presented. The significance of each elemental substitution at different atomic sites are suggested. Effects of Pb and Sb substitution are discussed in terms of average Cu valence. Behavior of transport critical current density J_c with temperature was explained using a self-field approximation.