CHARACTERISTICS OF BI-PB-SR-CA-CU-O POWDERS PRODUCED BY AEROSOL DECOMPOSITION AND THEIR RAPID CONVERSION TO THE HIGH-TC PHASE

Bi-Pb-Sr-Ca-Cu-O powders were produced by aerosol decomposition of nitrate solutions. The effects of reactor temperature and residence time on particle morphology and evaporative Pb loss from particles were demonstrated, and conditions necessary to control Pb loss established. Pb loss was roughly proportional to residence time, and minimal loss occurred with short residence times (3s) and T less-than-or-equal-to 800-degrees-C. Particles produced at 700-degrees-C typically contained significant porosity, while those produced at T great-than-or-equal-to 800-degrees-C were solid. Mixtures of the Bi2Sr2CuOy (2201) and Bi2Sr2CaCu2Oy (2212) phases were produced at 700-900-degrees-C in nitrogen and air. However, after heating in air for 16 h at 850-degrees-C, pellets of powder produced at 700-degrees-C with nominal composition Pb0.44Bi1.8Sr2Ca2.2Cu3Oy converted to approximately 79 vol.% of the Bi2Sr2Ca2Cu3Oy (2223) phase and displayed a T(c) (onset) of 110 K. Rapid conversion to 2223 was promoted by powder synthesis conditions, leading to controlled Pb loss and a homogeneous fine-grained dispersion of mixed-oxide precursor phases within particles.