AC susceptibility and electrical properties of Ta substituted (Tl1−xTax)(BaSr)CaCu2O7 superconductor (x = 0–0.3)

Abstract

The effects of Ta substitutions on the superconducting properties of (Tl1−xTax)(BaSr)CaCu2O7 for x = 0, 0.1, 0.2 and 0.3 are reported. X-ray diffraction patterns showed a single Tl-1212 phase for the x = 0 samples. Unreacted Ta2O5 peaks were observed in all Ta substituted samples. The electrical resistance versus temperature curves showed metallic normal state behavior. The transition temperature and maximum intergrain Josephson current decreased for x = 0. 1 and 0.2 but increased for x = 0.3 samples. The intergranular critical current density, Jc at the peak temperature, Tp of the imaginary part of the susceptibility was between 15 and 22 A cm−2. The x = 0.3 samples showed an increase in Tp indicating the enhancement of inter-grain coupling. The Josephson coupling energy, EJ showed that the intergranular coupling and flux pinning energy decreased for x ≤ 0.2 but increased for x = 0.3 samples. The roles of Ta2O5 in the Tl(BaSr)CaCu2O7 superconductors are discussed.