Abstract: Carbonaceous materials based on the fullerene molecules have been developed which allow for high conductivity (comparable to or higher than those attained by n-type doped polyacetylene). The fullerene materials are soluble in common solvents.

Abstract: A superconducting material higher in superconducting transition temperature and superconducting volume ratio than any conventional one is provided, which comprises a fullerene doped with rubidium and cesium. This fullerene system superconducting material makes it possible to improve both the superconducting transition temperature and superconducting volume ratio by having rubidium and cesium doped thereinto compared with any conventional fullerene systems. If the chemical composition of this super conducting material is expressed as Rb.sub.x Cs.sub.y C.sub.n, x and y are arbitrary if an equation x+y=3 is satisfied, preferable to be x=2 and y=1, further preferable to be x=1 and y=s. The superconducting transition temperature Tc and superconducting volume ratio when x=1 and y=2 or x=2 and y=1 are superior to those when x=3 and y=0 or x=0 and y=3, respectively.

Abstract: An oxide superconductor comprises a composition represented by the composition formula: (Nd.sub.x --Ce.sub.y --L.sub.z).sub.2 CuO.sub.4-d (wherein L is an element selected from Ca and Mg, and x+y+z=1). The compositions of Nd, Ce and L of the oxide superconductor corresponds to a point falling inside an area of Nd--Ce--L ternary diagram surrounded by straight lines (A-B), (B-C), (C-D) and (D-A) connecting point (A) with point (B), point (B) with point (C), point (C) with point (D) and point (D) with point (A), respectively, the points (A), (B), (C) and (D) being points (x=1, y=0, z=0), (x=0.4, y=0.6, z=0), (x=0.4, y=0.3, z=0.3) and (x=0.1, y=0, z=0.9), respectively, in the Nd--Ce--L ternary diagram. Above-described Nd--Ce--L--Cu--O oxides can exhibit superconductivity within a wide range of composition when heat-treated in an atmosphere of nitrogen.

Abstract: There is disclosed an improved process for preparing a superconducting composition having the formula MBa.sub.2 Cu.sub.3 O.sub.x wherein M is selected from the group consisiting of Y, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb and Lu; x is from about 6.5 to about 7.0; said composition having a superconducting transition temperature of about 90 K.; said process consisiting essentially of mixing ba(NO.sub.3).sub.2, M.sub.2 O.sub.3 and CuO in an atomic ratio of M:Ba:Cu of about 1:2:3 to form a precursor powder and heating the precursor powder in an oxygen-containing atmoshpere at a temperature from about 875.degree. C. to about 950.degree. C. for a time sufficient to form MBa.sub.2 Cu.sub.3 O.sub.y, where y is from about 6.0 to about 6.4; and maintaining the Mba.sub.2 Cu.sub.3 O.sub.y in an oxygen-containing atmosphere while cooling for a time sufficient to obtain the desired product.