Introduction of pinning centres in Tl-based 1212 and 1223 superconductors: bulk and thin films

Abstract
Introduction of pinning centres into high temperature superconductors is prerequisite to obtain a high critical current density (Jc) in magnetic fields. A process called melt-assisted pinning was developed to introduce pinning centres into Tl-based superconductors, the (1223) and (1212) phase of Tl-Sr-Ca-Cu-O system. The nominal composition is (Tl0.5Pb0.5)(Sr0.8Ba0.2)2Ca2Cu3O9. The intragrain Jc measured from magnetization was found to be 2*104 A/cm2 at 77 K and 1 tesla. Thin films of Tl-(1212) and Tl-(1223) were also prepared by the laser ablation method. It is emphasized that pinning centres was introduced more easily into the Tl-(1223) phase than into the Tl-(2223) phase of the Tl-Ba-Ca-Cu-O system.