PROPERTIES OF ALIGNED YBA2CU3O7-DELTA SUPERCONDUCTOR AS A FUNCTION OF OXYGEN DEFICIENCY-DELTA

Systematic studies of flux pinning and intragrain critical current J(c) were conducted in magnetically aligned, sintered Y1Ba2Cu3O7-delta material as a function of oxygen deficiency delta in the range 0 approximately 0.2. The essential findings are: (1) maximum J(c) occurred at full oxygenation, i.e., J(c) and pinning decreased steadily as oxygen was removed; (2) the irreversibility line B(irr)(T,delta) was degraded with the introduction of oxygen defects; (3) this degradation was strongly correlated with the reduction of J(c)(delta), implying that the irreversibility line is determined by the strength of the flux pinning defects; (4) the condensation energy F(c) decreased significantly with delta, indicating a rapid weakening in the effectiveness of preexisting pinning centers; (5) both lambda and xi increased as oxygen was removed, while (6) their ratio K and the superconductive anisotropy parameter gamma = (lambda(c)/lambda(ab)) almost-equal-to 5 varied little for delta less-than-or-equal-to 0.2.