Dysprosium doped Tl-1212 superconductors with varying Pb content

Dy-doped Tl-1212 superconductors with varying Tl stoichiometry (TlxPb1 x)(Ba0.05Sr0.95)2(Ca0.8Dy0.2)Cu2Oz (x = 0.2, 0.4, 0.5, 0.6, 0.8, 1.0) were fabricated by a two step procedure. Tl-free precursors were prepared by a wet chemical malic acid gel method, followed by vapor phase thallination at temperatures between 880 and 920 °C. X-ray diffraction was employed to determine the phase-purity of the samples. The best critical temperatures were obtained for samples with x: 0.4, 0.5 and 0.6. Tc(0) values up to 100 K could be obtained for samples with the composition (Tl0.4Pb0.6)(Ba0.05Sr0.95)2(Ca0.8Dy0.2)Cu2Oz sintered at 915 °C. Lower Tl stoichiometry resulted in secondary phases, higher Tl stoichiometry led to a decrease in the superconducting properties.