RUTHENIUM-BASED LAYERED CUPRATES RUSR(2)LNCU(2)O(8) AND RUSR2(LN(1-1-X) CU2O10 (LN=SM, EU AND GD)(X) CE)

We synthesized layered cuprates where the intermediate layer between t he CuO2 blocks consists of vertex sharing RuO6 octahedra. The (idealiz ed) stoichiometries of these compounds are RuSr(2)LnCu(2)O(8) (Ru-1212 ) and RuSr2(Ln(1+x)Ce(1-x)) Cu2O10 (Ru-1222), where Ln is one of the t hree neighboring lanthanides Sm, Eu and Gd. The analogy to the isostru ctural Nb based compounds, as well as simple valence counting, suggest that Ru is pentavalent in these compounds. Both 1212 and 1222 compoun ds are semiconducting when prepared in air and rapidly cooled to room temperature. Metallic behavior and superconductivity can be achieved f or various compositions upon appropriate annealing.