Enhanced Superconductivity in the Tl1?XBiXBa2Ca2Cu3Oy System

Compounds of the system, Tl_1–xBi_xBa₂Ca₂Cu₃O₉, were synthesized and studied. Bi substitutes at the Tl-site for values of x up to x=0.2. The superconducting transition temperature, T_c, increases from 110K for x=0.0 to 116K for x=0.2. SEM images reveal a plate-like morphology which is highly suitable for powder-in-tube processing. M-H loops show that the Bi-substituted phase has significantly better low temperature flux pinning properties than the pristine Tl-cuprate, and exhibits only a weak dependence on temperature and field when compared to that of unsubstituted phase. The J_c values calculated using the Bean model are: 3 × 10⁷ A/cm² at 10K,1T and 2 × 10⁴ A/cm² at 77K.1T. Substitution of 20% of Bi in TlBa₂Ca₂Cu₃O₉ makes the compound an excellent choice for magnet wire applications at relatively low temperatures.