SYNTHESIS STRUCTURE AND SUPERCONDUCTIVITY IN ALL-PEROVSKITE-LAYERED TITANIUM CUPRATES

A study on the reaction pathways, the synthesis, and the range of stab ility of complex perovskites in the system Ln-(Sr/Ba)-Cu-Ti is reporte d. Several possibilities for the Cu:Ti stoichiometry were explored wit h the aim of isolating potentially superconducting layered phases. A b ulk superconducting phase of the formula YSr2Cu2.7Ti0.3O8-delta with a T-c of 26 K was isolated and a whole family of layered oxides of the formula Ln(2)Ba(2)Cu(2)Ti(2)O(11-delta) was characterized. We have det ermined the limits of this family which extends from Ln = La to Tb. Th e studies reported include X-ray and electron diffraction, and TGA and magnetic susceptibility measurements. Structural and magnetic correla tions for these oxides are analyzed. (C) 1995 Academic Press, Inc.