Expedited Award for Novel Research: Preparation of High Tc Superconductors Through Chemical Processing Involving Microemulsions

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A novel technique for the production of uniform, ultrafine (~100), dense, monodispersed superconducting ceramics is undertaken in this expedited award. This method exploits the ability of single compartment water-in-oil microemulsions to form a highly selective barrier between its exterior and interior, thus creating a microvolume reactor in the emulsion microdroplets space. By appropriate processing, coprecipitation of the mixed metal hydroxides (precursors of the superconducting, ceramics) can be induced in the internal region of these microemulsions only. A mixed metal chloride solution consisting of precalculated ratios of Cu++, Cu+, Ba++, and Y+++ ions along with ~1 percent w/w dipalmitoyl phosphatidylcholine will be sonicated at slightly above the lipid gel-liquid phase transition temperature to encapsulate some of the metal and chloride ions inside the water-in-oil microemulsion. This collaborative project with the University of Rhode Island represents the first attempt at using single compartment vesicles for coprecipitation of metal hydroxides which are precursors for the recently discovered high temperature superconducting ceramics. The critical transition temperature as well as the critical magnetic field strength are intimately related to the stoichiometry and composition of the ceramic phase. These can be varied easily in the proposed technique by changing the ratio of the cations in the original solution. In contrast, however, the critical current density depends upon the processing steps used to obtain the final product. By producing ultrafine, dense and uniform particles, it is expected that higher critical current density will be obtained than that presently available with sintered superconducting ceramics.