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.