Transport critical current density and microstructure in extruded YBa2Cu3O7−x wires processed by zone melting

YBa2Cu3O7−x compounds were extruded into long wires with the diameter of 1 mm after sintering. The sintered wires were subsequently zone melted to develop a highly textured microstructure. Magnetization experiments at 77 K indicated a Jc value of 1×105 A/cm2 at 1 T. Transport measurements at 77 K showed a greatly enhanced field dependence of the critical current density. Transmission electron microscopy revealed an important grain‐boundary feature which eliminated the weak‐link behavior. Large amounts of dislocations have also been found in the zone‐melted sample which may contribute to flux pinning in the system.