Increase in the flux-pinning energy of YBa2Cu3O7−δ by shock compaction

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Abstract
Magnetic flux relaxation data on a composite specimen of YBa2Cu3O7−δ +Ag shock compacted at 167 kbar show that the flux‐pinning energy at 70 K and 10 kOe is enhanced by a factor of 2–3. This enhancement persists after annealing at 890 °C in oxygen for 24 h. The increased pinning energy is apparently caused by shock‐induced 〈100〉 and 〈110〉 line defects having a density up to 1012 cm−2. Annealing replaces line defects with (001) extrinsic stacking faults having displacement vectors of 1/6[031]. The average separation of the stacking faults in the [001] direction is 0.04 μm, which is comparable to the separation between fluxoids at 10 kOe. These results indicate that intragranular critical current densities can be increased significantly in bulk materials by shock processing. High densities of flux‐pinning sites could be induced efficiently in industrial‐scale quantities of bulk high Tc oxides by explosives.