Structural and superconducting properties of Bi 2Sr 2Ca 1− xCe xCu 2O y

Abstract

The structural and superconducting properties of Bi 2Sr 2Ca 1− x Ce x Cu 2O y (0≤x≤0.4) system are reported. Slow increase in normal state resistivity and decrease in superconducting transition temperature, T c is observed with increasing x for x ≤ 0.1. The T c depression rate is unusually high in comparison to the other rare earth dopants at Ca site for 0.1 < x <0.2. Metal-Insulator transition is observed at around x=0.2. The conduction mechanism in the semiconducting samples is found to be Variable Range Hopping. However, it is not possible to distinguish whether the hopping is in 2D or in 3D. From the decrease of c-lattice parameter with increasing x, the existence of Ce predominantly in +4 valence state is inferred. The hole filling mechanism is likely to be responsible for the T c depression and Metal-Insulator transition.