Properties of aligned YBa2Cu3O7−δ superconductor as a function of oxygen deficiency δ

Abstract

Systematic studies of flux pinning and intragrain critical current Jc were conducted in magnetically aligned, sintered Y1Ba2Cu3O7−δ material as a function of oxygen deficiency δ in the range 0 ˜ 0.2. The essential findings are:

1. (1) maximum Jc occurred at full oxygenation, i.e., Jc and pinning decreased steadily as oxygen was removed; 2. (2) the irreversibility line Birr(T, δ) was degraded with the introduction of oxygen defects; 3. (3) this degradation was strongly correlated with the reduction of Jc(δ), implying that the irreversibility line is determined by the strength of the flux pinning defects; 4. (4) the condensation energy Fc decreased significantly with δ, indicating a rapid weakening in the effectiveness of pre-existing pinning centers; 5. (5) both λ and ξ increased as oxygen was removed, while 6. (6) their ratio κ and the superconductive anisotropy parameter γ = (λc/λab) ≈ 5 varied little for δ