Buffer layers and thallination of Tl-based superconductors on flexible metal substrates

Reported here is the development of textured buffer layers that are compatible with Tl-based superconductor (SC) films on metallic substrates. Crucial properties for the successful development of a suitable buffer layer are appropriate lattice match, chemical stability, and a high degree of texture. Buffer layer materials investigated include cerium oxide, strontium titanate (STO), lanthanum aluminate (LAO), and lanthanum nickel oxide (LNO) which were grown using a pulsed excimer 248 nm laser deposition system equipped with multitarget and controlled ambient capabilities. The influences of substrate temperature and ambient pressure and flow on buffer layer growth are analyzed via XRD and AFM characterization. Highly textured buffer layers have been fabricated including epitaxial LAO/LNO/CeO/sub 2//Ni RABiTS configurations. Also reported are the results of thallination of Ba-Ca-Cu-O precursors on single crystal and buffered substrates using a hybrid 2-zone furnace. The hybrid 2-zone combines the advantages of crucible and standard 2-zone thallination processes. High quality Tl-1223 films with J/sub cm//spl sim/6.0 MA/cm/sup 2/ (0 T, 5 K) and 4.6 MA/cm/sup 2/ (0 T, 76 K) have been produced using the hybrid method.