Infrared zone melting process for YBa2Cu3O7−δ wires

Abstract

A novel process for the continuous densification of YBa2Cu3O7−δ wires by infrared zone melting is presented. Superconducting ceramic wires with moderate porosity (20–40%) were passed through a high temperature infrared zone at a speed of 1–2 cm/min, which resulted in zone melting followed by fast solidification to give near zero porosity wires. The atmospheric conditions during zone melting had a significant effect upon the resultant properties and microstructure of the wires. The best results were obtained for infrared zone melting under a vacuum that resulted in the decomposition of the superconducting phase into four phases without significant macroscopic chemical segregation across the wire. Subsequent conventional sintering and annealing treatment of such wires fully restored them to polycrystalline YBa2Cu3O7−δ wires having 96% of the theoretical density. The maximum transport critical current density obtained for such wires at 77 K in zero magnetic field was 2.65 × 103 A cm−2. Normalized critical current values as a function of magnetic field indicated that the quality of the intergrain connections for vacuum infrared zone melted wires was significantly better than that for conventionally processed wires and tapes.