The structural and superconducting properties of R1-2xCaxThxBaSrCu3O7-delta (R = Eu or Dy; 0.0 <= x <= 0.1)

We have investigated the effect of simultaneous substitution of equal amoun ts of Ca2+ and Th4+ at the R site, on the structural and superconducting ch aracteristics, in RBaSrCu3O7-delta (R = Eu or DY) by X-ray diffraction anal ysis, ac susceptibility, Je magnetization and de electrical resistivity mea surements. A linear and sharp drop in T-c, with increasing dopant concentra tion x was observed in both the compounds despite the charge-conserving (pr esuming that R is in 3+ state) and non-magnetic nature of the dopants. The observed decrease can be attributed to the disorder induced in the compound s by doping.