Textured composite Bi2Sr2Ca1Cu2O8+a (2212) conductors have been fabricated by a novel method termed composite reaction texturing (CRT) that makes use of inert whiskers or fibers to align superconducting grains and control their morphology. The process has two stages, the initial alignment of fibre material in a precursor followed by a composite reaction stage to develop a textured microstructure. In this work, disk-shaped pellets with whisker alignment in the pellet plane were reacted to produce CRT material with a transport critical-current density in excess of 4×103 A cm−2 at 77 K (B=0). At 4.5 K, the critical-current density was ∼105 A cm−2 in zero field and 2.104 A cm−2 at 12 T. The method clearly has promise for the production by a wind-and-react technique of high critical-current conductors with large cross sections.

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An analysis of brick-wall-like structures in high T, polycrystalline ceramics with elongated grains is presented in order to predict and explain the voltage-current (V-I) characteristics in these materials. The current path is determined by two different critical current densities in the direction of the long and short dimensions of the grains. The resistive transition and the n-values are studied in the limit of no longitudinal current transfer by using a statistical analysis of the distribution of the critical currents. This simple case illustrates the different aspects of the problem of modelling the general and more complicated structure.

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Textured Bi2S~CalCu208+~ (2212) conductors have been fabricated by a novel method termed Composite Reaction Texturing (CRT) that makes use of inert whiskers or fibres to align superconducting grains and control their morphology. The process has two stages, the initial alignment of fibre material in a precursor followed by a composite reaction stage to develop a textured ceramic microstructure. Although strong texture and high critical current densities have been reported previously using this method the detailed mechanism for microstructure development was not clear. In this work two different methods of achieving fibre alignment are compared, variations in the resulting microstructures after composite reaction provide information on the mechanism of microstructure development. Disc-shaped pellets of 2212 with random MgO whisker alignment in the pellet plane are compared with polymer processed material with uni-directional whisker alignment. Although the resulting textures are strikingly different, the transport current densities are high for both materials, in excess of 2.104 A cm-2 at 4.5K and 12T for each material. Samples with dimensions up to 200mmxlOOmmx2mm have been fabricated and the method clearly has promise for the production by wind-and-react or form-and-react techniqpes of high critical current conductors with large cross-sections, as well as complex shapes.