Nanorod-superconductor composites: A pathway to materials with high critical current densities

Most large-scale applications of the high-temperature copper oxide superconductors (HTSCs) require high critical current densities (J(c)'s) at temperatures near the boiling point of liquid nitrogen to be technologically useful, although thermally activated flux flow reduces J(c) dramatically at these temperatures. This intrinsic limitation can be overcome by introducing nanometer-sized columnar defects into an HTSC. Nanorods of magnesium oxide were grown and incorporated into HTSCs to form nanorod-HTSC composites. In this way, a high density of nanorod columnar defects can be created with orientations perpendicular and parallel to the copper oxide planes. The J(c)'s of the nanorod-HTSC composites are enhanced dramatically at high temperatures and magnetic fields as compared with reference samples; these composites may thus represent a technologically viable strategy for overcoming thermally activated flux flow in large-scale applications.