High-pressure synthesis and J(c)-related properties of Cr- and V-based high T-c superconductors

Homologous series of cuprate superconductors (Cu,Cr)Sr2Can-1CunO2n+3 [(Cu,C r)-12(n-1)n, n=1-9] and (Cu,V)Sr2Can-1CunO2n+3 [(Cu,V)-12(n-1)n, n=3-7] pre pared under high pressure were discussed. They have M-12(n-1)n-type structu res with the: M site occupied by the (Cu,Cr) [or (Cu,V)] mixed atom. The hi ghest T-c in each series is 103 K for (Cu,Cr)-1223 and 107 K for (Cu,V)-123 4. The n=3 phases of both series show extremely high critical current densi ties and irreversibility fields which are comparable to or better than thos e of the YBa2Cu3O7. This seems to be related to the partial occupation of t he Cu atom in the charge reservoir layer and the random arrangement of Cu a nd Cr (or V) there. (C) 2000 Elsevier Science B.V. All rights reserved.