The present invention concerns the improvement of the supercurrent carrying capabilities, i.e. the increase of critical current densities, of bicrystalline or polycrystalline superconductor structures, especially of high-Tc superconductors. By providing an appropriate predetermined dopant profile across the superconductor structure, in particular within or in the vicinity of the grain boundaries, the space-charge layers at the grain boundaries are reduced and thereby the current transport properties of the superconductor significantly improved. Simultaneously, the influence of magnetic fields on the critical current densities is significantly reduced, which in turn enhances the overall supercurrent carrying capabilities while keeping the supercurrent transport properties of the grains at good values.