Improved press forging of Ba sub 2 YCu sub 3 O sub 7 superconductor.

An improved press forging technique has yielded ceramic Ba sub 2 YCu sub 3 O sub x with a very high degree of orientation and mechanical integrity. The as forged samples are dense and tetragonal and have an oxygen content of ~6.3. By a partial oxidation of the samples, a superconducting skin 20-50micron thick is formed on the outer surface. Transport measurements on this skin show a J sub c > 3000A/cm sup 2 with an improved field dependence as compared with randomly oriented samples. The restriction of oxidation to the thin outer skin has reduced the microcracking which accompanies the oxidation of tetragonal Ba sub 2 YCu sub 3 O sub x.