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

摘要

Samples of Bi_(2)Sr_(2)CaCu_(2-x)Co_(x)O_(8+delta) (Bi-2212, x(velence)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 67K and transport current density (Jc) has been increased from 4.67 X 10~(2) to 3.52 X 10~(3) 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 ((chi)_(ac)) was found to be -2 X 10~(-6) and the upper & lower critical magnetic field (Hc_(1) & Hc_(2)) values were found to be approx0.05T & 4.2T) respectively.