Phase evolution studies of (TI,Pb)(Sr1.6Ba0.4Ca2Cu3Oy superconductors

Optimum compositions that lead to (Tl1−xPbx)(Sr1.6Ba0.4)Ca2Cu3Ag0.4Oy (referred to as Tl,Pb-1223) phase evolution have been identified. The Tl-free precursor powders with the composition Sr1.6Ba0.4Ca2Cu3Ag0.4O7 were prepared in an aerosol flow reactor. These precursor powders were then mixed with appropriate amounts of T12O3 and PbO, pressed and wrapped in a gold foil, and introduced into a furnace kept at 920 °C where they were held at 920 °C for 2 hours before being slow cooled to room temperature in 4–5 hours under flowing oxygen. X-ray data showed that single-phase Tl,Pb-1223 can be obtained in the range x = 0.3–0.5. All the samples studied were found to be superconducting. The Tc (diamagnetic onset) for Tl,Pb-1223 single phase varies from 105 K to 116 K for the as-synthesized samples.