Effects of substitutions of copper at the chain site on the transport and magnetic properties of YBa2Cu2(Cu1-xMx)O6+w

We prepared polycrystalline samples of YBa2Cu2(Cu1-xMx)O6+w, where M (= Sc, Cr, V, Fe, Al and An) substitutes copper in the chain site, and measured t heir transport and magnetic properties. The substitution level x was 0.05 a nd 0.10 for each substituent. We determined the solubility of the different metals and the dependence of T-c, irreversibility lines and critical curre nt density j(c) on M and x. An improvement of j(c) by a factor larger than 2 was obtained in the Fe-, Al-, Cr- and V-substituted materials. No improve ment of the irreversibility line was obtained for any substituent.