Critical aspects on preparation of Bi-2223 glassy precursor by melt-process

It is well known that many Bi-Sr-Ca-Cu-O compositions are glass forming and are converted into high-critical temperature superconductors after proper annealing. Glassy precursors have been prepared by rapid quenching of nominal Bi2Sr2Ca2CU3O10 melts from above 1000 degrees C in air using different conditions. In order to fabricate superconductors having high-critical temperature and current density using the glass-ceramic route, it is necessary to clarify the total chemical composition of the quenched glasses. For the first time the total chemical composition of such melts has been directly investigated by element analysis. The oxygen content has been directly measured by carrier gas hot extraction of as-quenched melts. The investigated cation content in as-quenched nominal Bi2Sr2Ca2CU3O10 Melts presents significant deviations in composition for the glassy precursor, foremost for the calcium content. The main reasons of the non-complete transition from nominal to obtained composition after the quenching step was showed to be due to inhomogeneous and incomplete melting. This dependency is showed to be highly affected by the nominal composition of the melt. From literature there are barely any published values of the chemical composition of the quenched glassy precursors that would however be critical to control the crystallization behavior and to understand the influences on the superconductive properties. (C) 2007 Elsevier B.V. All rights reserved.