Preparation and properties of superconducting crystallized glasses and enamels based on the Bi-Sr-Ca-Cu-oxide system

Only short time after the discovery of the BiSrCaCu-Oxide (BSCCO) group of superconductors, it was found that a glass-ceramic route could be applied to the preparation of the BSCCO materials. Following this route, melts were rapidly quenched and the superconducting phases were crystallized by subsequent annealing of the glasses under appropriate conditions. The glass-ceramic route has the following advantages: Good formability (e.g. production of long fibers), ability to generate composite systems (e.g. enamelling technique) continuous processes, controlled nucleation and crystallization, integration of texturing procedures (e.g. directional solidification, laser melting), higher strength and density of the superconducting components. During the preparation of the glasses we encountered two major problems. The first one was the segregation of CaO, the second the rapid cyrstallization of parasitic phases (e.g. alkaline-earth cuprates). The achievement of homogeneous glasses without inclusions by means of an additive, the crystallization of the 80 K and 110 K phases from these glasses and the results of a study of the enamelling technique for a BSCCO/Ag tape system are reported in the following. (orig.)