PREPARATION, THERMAL-PROCESSING BEHAVIOR, AND CHARACTERIZATION OF YBCO FROM FREEZE-DRIED NITRATE PRECURSORS

YBCO was synthesized using atomically mixed nitrate precursors. Atomic mixing was achieved using a freeze-dried process which is fully discussed here. The thermal processing behavior of these precursors is fundamentally different from that of mechanical mixtures of the Y, Ba, and Cu oxides and it is examined in detail. Ba2Cu3O5+x (normally considered a high oxygen pressure phase) and Y2O3 formed as nitrate decomposition products at ambient atmospheric conditions. Subsequent reaction of these materials (2 h at 925-degrees-C) produced polycrystalline YBCO. Without any post-processing of the powders, product YBCO powders consisted of 30-mu-m agglomerates composed of crystals 1-3-mu-m on an edge. The powdered products exhibited a magnetic susceptibility greater than 90% - 1/4-pi.