FLUX PINNING and PROPERTIES OF SOLID-SOLUTION (Y, Nd){sub}(1+x)Ba{sub}(2-x)Cu{sub}3O{sub}(7-δ) SUPERCONDUCTORS PROCESSED IN AIR and PARTIAL OXYGEN ATMOSPHERES

摘要

The effect of chemical composition substitutions on the flux pinning and physical properties of (Y, Nd){sub}(1+x)Ba{sub}(2-x)Cu{sub}3O{sub}(7-δ) superconductors was studied in powders processed by solid-state reaction and equilibrated in air at 910°C. The powders were subsequently processed in 1% O{sub}2 atmosphere at < 920°C to increase the superconducting transition temperature (T{sub}c) and critical current density (J{sub}c). After processing in air, the powders were nearly pure single-phase compositions as determined by X-ray diffraction. Powders were finally annealed in 100% O{sub}2 atmosphere at temperatures < 500 °C to maximize T{sub}c. The T{sub}cS of the powders were measured by ac susceptibility and dc magnetization methods. Annealing powders with a final step in 1% O{sub}2 atmosphere compared to processing in air significantly enhanced T{sub}c from 65-90 K to > 92 K for all compositions tested, and also increased J{sub}c from about ～10{sup}3-10{sup}5 A/cm{sup}2 to ～10{sup}6 A/cm{sup}2. The flux pinning properties varied depending on exact composition, and the intrinsic behaviors changed with the final 1% O{sub}2 annealing treatment