BI-PB-CA-CU-O SUPERCONDUCTOR FILMS ON SINGLE-CRYSTAL GARNET SUBSTRATES

The use of garnet as substrates for growing high temperature superconductor films of Bi-Pb-Sr-Ca-Cu-O (BPSCCO) system is reported here. Thick films of BPSCCO with a prevalently high T(c). phase were successfully prepared on Gadolinium Gallium Garnet (GGG) substrates using the screen printing technique. The formation of superconducting phase on these substrates needed much lower heat treatment temperatures (30-40C lower than used for most known substrates) and heating time. Heat treatment at 800C for 2-6 hours was sufficient to give good a-b oriented films with a single sharp transition at 100K, having mostly a high T(c) phase. Films annealed at higher temperature showed two step transition and mixed phases. The microstructural, electrical, superconducting and cross sectional studies for interaction between film and substrate and their dependence on heat treatment temperatures are also reported here.