Effect of Ba Substitution on the Superconducting Properties and the Irreversibility Line of the Compounds TIPb 1223: Tl 0.5 Pb 0.5 (Sr 2−x Ba x )Ca 2 Cu 3 O 9−δ

Abstract

The superconducting properties and the irreversibility line of the Tl0.5Pb0.5(Sr2−xBax)Ca2Cu3O9−δ were studied by ac susceptibility on both ceramic and powdered samples. The samples were prepared by solid state reaction in flowing oxygen at 880°C or in sealed quartz tube at 960°C. The irreversibility lines were measured up to 4 Tesla and were determined by the maximum of the X″ peak, using the same ac field to allow comparison between them. The presence of the 1212 phase as a minor superconducting phase was clearly evidenced in all cases. The case of samples of TlPbl223 with Tl/Pb ratio different from unity was also examined.