Superconductor with enhanced current density and method for making such a superconductor

The present invention relates to the current carrying capabilities of superconductors and especially to the fact that the critical currents of many superconductors are limited by grain boundaries formed within such polycrystalline devices. The invention overcomes this limitation of present superconductors by using chemical alterations for improving the current transport properties of the superconductors' grain boundaries. With the aim of diminishing detrimental effects caused by space charge layers formed at the grain boundaries, this is done by doping the superconductors to dopant concentrations different from concentrations that would provide the optimum superconducting properties of the grains of the superconductors. The present invention concerns an enhancement of the supercurrent carrying capabilities of bicrystalline or polycrystalline high-Tsuperconductors, i.e. the critical current densities in such superconductors. The current transport properties are improved by chemically altering, especially doping, the superconductors. It seems that a modification of the space-charge layers at the boundary, e.g. by an increase of the mobile charge carrier concentrations particularly in the superconductor's grain boundaries, which concentrations differ from those resulting in optimum superconducting properties of the grains, are responsible for this positive effect.