Control of Precursors for BSCCO Powder-in-Tube Process by Cryoprocessing
Critical current densities of Bi-2223 tapes made by the oxide-powder-in-tube (OPIT) process depend on the microstructure of the superconductor. Conventional ceramic synthesis techniques lead to a multiphase microstructure with large second phase particles and poor grain alignment, which can disrupt the path for current transport. To overcome the limitations of conventional processing, a cryoprocessing technique (freeze-drying) was developed, which provided control of the phase assemblage to be packed into the Ag tubes before mechanical working. The freeze-drying process resulted in intimate mixing of CaCuO2 and Bi1.8Pb0.4Sr2CaCu2Oz and led to rapid formation of the 2223 phase with a minimum of impurity phases. The process allows for the large scale synthesis of precursors specifically tailored to the manufacture of long lengths of tapes by the OPIT process.
KeywordsCritical Current Density Impurity Phase Current Transport Heat Treatment Time Nitrate Precursor
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