FORMATION OF ANISOTROPIC TL-1212, TL-2212, TL-1223 AND TL-2223 PARTICLES USING AEROSOL FLOW REACTED POWDERS

Highly anisotropic particles of Tl-1212, Tl-2212, Tl-1223 and Tl-2223 superconductors were grown. The Tl-free precursor powders with tile co mpositions Ba1Ca2Cu3Ag0.37O6 and Ba2Ca2Cu3Ag0.37O7 were prepared using an aerosol flow reactor. These precursor powders were then post-annea led in 0.1 atm oxygen at 700 degrees C for 4h to reduce the carbon pre sent and mixed with Tl2O3 (typical composition of Tl-x; x = 0.6-1.0). The Tl-containing powders were heated in sealed gold tubes between 650 -890 degrees C for various times. X-ray diffraction showed that the Tl -2212 and Tl-2223 phases were stable over a wide range of temperatures . Scanning electron microscopy showed evidence for the presence of hig h aspect-ratio particles. These highly anisotropic particles may of in terest far the preparation of powder-is-tube and other powder deposite d couductors, for current leads, and for grain alignment studies.