High-pressure synthesis and superconducting properties of (Cu,Cr)-12(n-1)nand (Cu,V)-12(n-1)n series of phases

The Cr- and V-based cuprate superconductors were prepared under high pressu re conditions. The (Cu,Cr)Sr(2)Can(-1)Cu(n)O(2n+3) [(Cu,Cr)-12(n-1)n] phase s exist at 6 GPa for a wide range of n, n=1-9, while the (Cu,V)Sr2Can-1CunO 2n+3 [(Cu,V)-12(n-1)n] phases are stable for n=3-7. It was found that the S r atoms of the Cr-based series of phases can be substituted partially by Nd and such a substitution affects T-c depending on the n value. The variatio n of T-c variation with n of the Cr- V- and Nd-substituted phases are discu ssed in connection with the hole (carrier) concentration. Critical current densities (J(c)) under magnetic field of the (Cu,Cr)-1223 and (Cu,V)-1223 a re also discussed. Their J(c) values under 1 T are extremely high compared with other high T-c superconductors.