EFFECT OF SHOCK PRESSURE ON SUPERCONDUCTIVITY IN EXPLOSIVELY FABRICATED Y-BA-CU-O/METAL MATRIX COMPOSITES

Explosively fabricated (consolidated) powder of superconducting YBa2Cu3O7 and sintered (98% dense) and shock-loaded YBa2CU3O7 exhibit identical systematic changes in residual superconductivity with peak shock pressure. X-ray diffraction studies for explosively fabricated Y-Ba-Cu-O at pressures ranging from 4 to 19 GPa show characteristic split peaks at 2-theta almost-equal-to 32-degrees and 58-degrees to change in a systematic way: a reduction in specific reflection peaks and peak broadening with increasing shock pressure. The susceptibility ratio (chi/chi-0) (as an indication of the diamagnetic shielding signal) also decreases with increasing pressure, and the superconducting transition mid-point values (T(c)(1/2)) of the resistance-temperature (R-T) curves decrease with increasing pressure, indicating a broadening of the super-conducting transition since the T(c) start temperatures remain essentially constant (T(c)) almost-equal-to 90 K). Precipitate-like defect clusters with associated large strain fields are observed in the shock processed YBa2CU3O7 by transmission electron microscopy to increase in density with increasing shock pressure. These defects can phenomenologically account for the shock-induced degradation observed in Y-Ba-Cu-O without any significant orthorhombic-to-tetragonal structure transformation.