Superconducting fullerene nanowhiskers.

We synthesized superconducting fullerene nanowhiskers (C(60)NWs) by potassium (K) intercalation. They showed large superconducting volume fractions, as high as 80%. The superconducting transition temperature at 17 K was independent of the K content (x) in the range between 1.6 and 6.0 in K-doped C(60) nanowhiskers (K(x)C(60)NWs), while the superconducting volume fractions changed with x. The highest shielding fraction of a full shielding volume was observed in the material of K(3.3)C(60)NW by heating at 200 °C. On the other hand, that of a K-doped fullerene (K-C(60)) crystal was less than 1%. We report the superconducting behaviors of our newly synthesized K(x)C(60)NWs in comparison to those of K(x)C(60) crystals, which show superconductivity at 19 K in K(3)C(60). The lattice structures are also discussed, based on the x-ray diffraction (XRD) analyses.