Influence of oxygen deficiency on the superconductive properties of grain-aligned ${\mathrm{YBa}}_2$${\mathrm{Cu}}_3$${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$

Magnetically aligned samples of sintered ${\mathrm{YBa}}_2$ ${\mathrm{Cu}}_3$ ${\mathrm{O}}_{7\mathrm{-}\mathrm{\delta }}$ were used to test the effects of oxygen-deficiency δ (with δ≤0.2) on the superconductive magnetization M, critical current density ${\mathit{J}}_{\mathit{c}}$, irreversibility field ${\mathit{B}}_{\mathrm{irr}}$, upper critical field ${\mathit{H}}_{\mathit{c}2}$, coherence length ξ, condensation energy ${\mathit{F}}_{\mathit{c}}$, penetration depth λ, and related properties as a function of temperature T and applied field H∥c. In selected cases, studies were also made with H∥ab. The O content was monitored in situ by thermogravimetric analysis. The open porosity and granularity of the material allowed rapid and homogeneous oxygenation. We found no significant enhancement of intragrain ${\mathit{J}}_{\mathit{c}}$ with chain-site O defects. With few exceptions, maximum ${\mathit{J}}_{\mathit{c}}$ occurred at full oxygenation.