Effect of Site Selective Doping of Co on the Physical and Structural/Micro structural Properties of Bi-Based High Temperature Superconductors.

Samples of Bi2Sr2CaCu2-xCoxO8+δ (Bi-2212, x = 0.0 to 0.25) were synthesized by solid-state reaction route. The critical temperature (Tc) measured by standard four probe method has been found to depress from 80 K to 67 K and transport current density (Jc) has been increased from 4.67×102 to 3.52×103 Acm-2 as Co content (x) increases from 0.00 to 0.25. The structural / micro-structural characteristics of the melt textured materials investigated by transmission electron microscopy (TEM) exhibit planar defects in local region of Co-doped Bi-2212 system. These planar defects may act as flux pinning centers. From the magnetic properties measurement of the samples, the ac susceptibility (χac) was found to be -2×10-6 and the upper & lower critical magnetic field (Hc1 & Hc2) values were found to be ∼0.05T & 4.2T) respectively. [ABSTRACT FROM AUTHOR]