Effect of Post-Heat Treatment on the Critical Current Density of Nb₃Al Superconductor

Abstract

The achievement of stoichiometry is very important for Nb₃Al superconductor with excellent properties. A rapid heating, quenching, and transformation method is efficient to achieve stoichiometric Nb₃Al superconducting wires, and supersaturated solid solution phase was transformed to Nb₃Al in the transformation process with a post-annealing temperature between 800° to 900 °C and for 10 h. X-ray diffraction analysis revealed that the Nb₃Al wires were of pure Nb₃Al phase with a superconducting transition temperature about 18 K. Experimental results further showed that superconducting transition width was narrowed by quenching process after post-annealing. For the typical samples, the H _c2(T) was determined from the onset transitions of the M–Tcurves under various applied fields and the H _c2(0) value was extrapolated to be about 35 T. A significantly high J _c value under a magnetic field up to 9 T and at 8 K was observed. The pinning behavior of the Nb₃Al wires was also discussed.