ENGINEERED FLUX-PINNING CENTERS IN PB-DOPED HIGH-TEMPERATURE SUPERCONDUCTING BI2SR2CACU2O8 CERAMICS

The Pb solubility of ''Bi2Sr2CaCu2O8'' is determined within the concen tration range Bi2.18-xPbxSr2CaCu2O8+d with 0 less than or equal to x l ess than or equal to 0.6 and the temperature range from 800 to 900 deg rees C. From a consideration of the Pb solubility in ''Bi2Sr2CaCu2O8'' a simple annealing procedure was developed to precipitate (Pb, Bi)(4) (Sr, Ca)(5)CuO10+d (451 phase) in high-temperature superconducting Ph- rich ''Bi2Sr2CaCu2O8'' ceramics. The precipitation results in a two-fo ld increase of the critical current density which is believed to expre ss improved pinning properties of the superconducting ceramics. The mi crostructures of the samples with increased critical current density w ere studied with respect to the grain size and volume content of the 4 51 phase.