Fabricating polycrystalline high-Tc superconductors

Abstract

Many applications of high-temperature superconductors require the ability to carry large currents in high magnetic fields. Electrical properties of single crystals and thin films offer hope that suitable electrical properties will be obtained in polycrystalline materials. Novel microstructures can be produced by melt-recrystallization processes that can be characterized by oriented crystallites. The large critical current densities required for many applications have been demonstrated by powder-in-tube and melt-texturing processes. There are several competing processes to form bulk polycrystalline materials. Plastic forming techniques, such as extrusion and tape casting, offer the advantage of fabricating long and continuous coils. Nearterm products that operate in low magnetic fields include current leads, shielding devices and high-quality resonant cavities.

A sol-gel method for preparing oriented YBa2Cu3O7- deltafilms on silver substrates

“…A high degree of orientation in the films suggests that these films may have superior electrical properties. This nntion, however, has not been borne out in most of the films that have been prepared according to the precalcination and calcination programmes described previously [32]. Several 123 films of 1-8 pm in thickness have exhibited J , values of 2W1000 A cm12; the best film had a J , of 3500 A cm-2.…”