Superconductivity in high-Tc (Tl1−xSex)Sr2CaCu2O7 system

Abstract

Superconductivity up to 76 K has been achieved in Se substituted Tl-1212 phase, (Tl1−xSex)Sr2CaCu2O7. X-ray diffraction patterns showed the presence of Tl-1212 as the major phase in most samples. The highest volume fraction of Tl-1212 phase (88%) was observed in the x = 0.1 sample. The electrical resistance measurement showed the highest onset temperature, Tc−onset (76 K) for x = 0.2 and 0.4. AC susceptibility (χ = χ + iχ″) measurements showed the highest superconducting transition temperature Tcχ′ = 71 K for x = 0.4. The peak temperature, Tp of the imaginary part of the susceptibility, χ″ was also the highest for x = 0.4 sample (Tp = 69 K). The inter-grain critical current density at the peak temperature, Jc(Tp) for all samples was between 17 and 19 A cm−2. This work showed that in addition to Bi, Pb, Cr, V, Re and rare-earth elements, Se substitution for Tl also resulted in the formation of a superconducting material in the TlSr2CaCu2O7−δ phase.