Effect of Ca substitution on the superconductivity of La2.5Y0.5CaBa3(Cu0.88Fe0.12)(7)O-z

The structural and superconducting properties of single-phase La2.5-gammaY0 .5Ca1+gammaBa3 (Cu0.88Fe0.12)(7)O-z (LYCaBCuFe) (gamma = 0.0-1.0) compounds with triple perovskite structure are investigated using X-ray diffraction, resistivity, a.c. susceptibility, and oxygen content measurements. Increas ing Ca substitution for La resulted in a decrease in unit cell axes and vol ume. T-c(R=0) shows a marginal increase from 31 K to 37 K for gamma = 0.0-0 .21 and thereafter it decreases with increasing gamma leading to zero T-c(R =0) at gamma greater than or equal to 0.84. This shows that the suppression of T-c from 80 K to 31 K by Fe doping at x = 0.12 La2.5Y0.5CaBa3(Cu1-xFex) (7)O-z cannot be compensated by appropriate hole doping with Ca in LaYCaBCu Fe.