Enhancement in transport properties of seeded melt-textured YBCO by Cu-site doping

A significant research effort has been made worldwide to introduce nanometre-scale weak superconducting regions into seeded melt-textured superconductors to enhance their critical current density, trapped magnetic field and levitation force. The enhancement in these properties is dependent on the pinning forces exerted on the magnetic flux lines. In this paper we present a substantial improvement in the transport properties of these materials by optimizing the fabrication conditions, controlling the oxygen deficiency, as well as adjusting the doping level of Zn in YBa₂(Cu_1-xZn_x)₃O_7-δ large grains. The enhancement is found to be as much as 30% by doping between about x = 0.001 25 and 0.002 53. The results strongly indicate that the introduction of local nanometre-scale weak superconducting regions by Zn substitution for Cu in the CuO₂ plane enhances the transport properties. Due to the simplicity of the processing conditions, these doping techniques can have a significant potential for a variety of engineering applications.