Synthesis and properties of superconducting (Tl,Pb)-(Sr,Ba)-Ca-Cu-O thick films on Ag

摘要

We report successful texturing of screen-printed (Tl,Pb)-(Sr,Ba)-Ca-Cu-O thick (20 μm) films on both LaAlO3 and Ag foil using rapid thermal processing (RTP) followed by furnace annealing. An RTP cycle to ≈915°C for 20 seconds in Ar produces massive melting of the superconducting powder but not the Ag substrate. Subsequent annealing under O2 in sealed Au foil with a Tl source yields a brick-wall microstructure consisting of c-axis aligned, plate-like grains. X-ray diffraction and Meissner data show a mixture of the Tl-1223 and Tl-1212 phases while energy-dispersive spectroscopy identifies the plate-like grains as the desired Tl-1223. Magnetization data suggest intergranular supercurrents flowing across the entire film. Critical current densities inferred from hysteresis are 9×104 A/cm2 at 5 K in low fields, decreasing by a factor of 5 in 5 tesla.