FLUX-PINNING AND IRREVERSIBILITY LINES OF NEW OXYCARBONATE SUPERCONDUCTORS CU0.5C0.5)BA2CAN-1CUNO2N-1CUNO2N+3(N=3,4)(3(N=3,4) AND (CU0.5C0.5)(2)BA3CAN)

We estimated critical current densities J(c)'s and irreversibility fie lds B-irr's of new oxycarbonate superconductors, (Cu0.5C0.5)Ba2Can-1 C unO2n+3(n=3,4) and (Cu0.5C0.5)(2)Ba3Can-1CunO2n+3 (n=3,4). (Cu,C)-base d oxides, especially single (Cu,C)-layer oxides, showed less excellent flux pinning properties that other high-T-c oxide superconductors at low temperatures. The slopes of irreversibility lines for the single ( Cu,C)-layer oxides were steeper than those of the double (Cu,C)-layer oxides were steeper than those of the double (Cu,C)-layer oxides. This result can be understood by the difference of the distance between Cu O2 superconducting blocks, At 77K, B-irr of the (Cu,C)-1234 was 3.8T w hich was higher than that of Hg-1223 in spite of lower T-c of (Cu,C)-1 234. Neutron irradiation to (Cu,C)-1234 significantly enhanced both J( c) and B-irr. About 6x10(5)A/cm(2) at 77K in 1T was obtained after the irradiation, which was one of the highest J(c) ever reported for bulk superconductors.