Superlattice structures between YBa2Cu3O7-delta and (Pb,Cu)Sr-2(Ca,Y)Cu2O7-delta high-T-c cuprates

A solid solution range exists between the systems YBa2Cu3O7-delta and (Pb,C u)Sr-2(Ca,Y)Cu2O7-delta has been successfully synthesized. The microstructu res across the solid solution are complicated by the presence of an incomme nsurate or commensurate modulation. However, the studies indicate unambiguo usly that the structural modulation is neither a necessary nor sufficient c ondition for superconductivity among the composition across the solid solut ion. The modulation may be controlling the cation/oxygen positions in the c harge reservoir layers, originating from the different oxygen positions in the perovskite-type (123-type) YBa2Cu3O7-delta and the rock salt-type (1212 -type) (Pb,Cu)Sr-2(Ca,Y)Cu2O7-delta. The discovery of the superlattice stru ctures between YBa2Cu3O7-delta and (Pb,Cu)Sr-2(Ca,Y)Cu2O7-delta adds yet a further chemical dimension to these systems, and may extend the possible av enues of research not only for superconductivity but also for structural ch emistry. (C) 2000 Elsevier Science Ltd. All rights reserved.