SUPERCONDUCTIVITY AND POSSIBLE OVERDOPING IN LU1-XCAXBA2CU3O7-DELTA

Structural and superconducting properties of the system Lu1-xCaxBa2 CU 3O7-delta, both in bulk as well as thin film form, have been investiga ted. Presence of large Ca-ions at the Lu-sites is responsible for phas e stability (in 1-2-3 phase) in bulk. In argon annealed tetragonal sam ples (delta:1) superconductivity is reinstated as in these samples, pr esence of Ca-ions lead to the generation of holes in the Cu-O planes. In oxygen annealed bulk samples and thin films, there is a large depre ssion of T-c due to divalent Ca-ions present in concentration x < 0.2. Our data indicate that this depression of T-c is likely due to overdo ping effect.