Optimization of spray drying process for Bi-2223 precursor powders fabrication

Precursor powders for the fabrication of Bi₂Sr₂Ca₂Cu₃O_10+δ (Bi-2223) tapes were fabricated with spray drying technique combined with a one-step calcination process. During the spray drying process, the effects of spray temperature on both the morphology and carbon content of collected powders were systematically analyzed. And the uniformity of chemical composition of these powders was confirmed with EDX mapping. By optimizing the calcination temperature, precursor powders with the major phases of Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) and alkali earth cuprates (AEC, (Ca, Sr)_xCu_yO_z), proper Pb content, and uniform morphology were obtained. Powder in tube process was adopted for the fabrication of 37-filament Bi-2223 tapes and a traditional heat treatment process involving the first heat treatment, intermediate rolling and second heat treatment was performed, during which textured Bi-2223 phase was obtained. With the optimized fabrication parameters and spray dried precursor powders, 37-filament Bi-2223 tape was achieved with high critical current of I _c ~ 125 A. Further optimization involving with the over-pressure heat treatment process is on the way.