Texture and critical current anisotropy in composite reaction textured MgO whisker/Bi-2212 multilayer structures

Highly textured bulk Bi-2212/MgO whisker superconducting composites have been synthesised by four processing techniques followed by a partial melting treatment termed composite reaction texturing (CRT) and post-annealing. Composites with different characteristic whisker alignment resulted in different types of textured microstructure which enabled detailed study of the critical current density, J/sub c/, as a function of texture. Highest J/sub c/ values were achieved in samples with 10 wt% MgO whiskers aligned in a planar 2D arrangement, which led to string c-axis texture. High J/sub c/ anisotropy along different sample directions and for different field directions was observed in the highly textured samples, a similarity to the behaviour of Bi-2212 single crystals was seen in the most highly textured materials. The J/sub c/ of the c-axis textured samples was self-field limited and could reach 3200 A/cm/sup 2/ at 77 K and 4 mT. Magnetisation measurements indicated a J/sub c/ in excess of 5.10/sup 4/ A/cm/sup 2/ at 5 K and 12 T.>