Effect of Boron Doping in Bi-based 2223 Superconductors

Samples with the stoichiometric composition Bi_2?xPb_xSr₂Ca₂Cu_3?yB_yO_z (x = 0.3, y = 0.2, 0.25, 0.3, 0.4) ceramics were prepared by a solid state reaction method. The samples were annealed at 850 °C for 100 hours (treatment A), and the other at 850 °C for 200 hours (treatment B). From the X-ray diffraction data of a ceramic sample it is revealed that all the samples were mixed phases of 2212 and 2223. The variation of the lattice parameters with the dopant level are represented. From the D.C. four-probe electrical resistivity data it was found that for the samples subjected to treatment B the T_c(0) values were higher than those with treatment A. The A.C. susceptibility data were collected by change in the inductance method. The effect of boron doping on the phase formation and T_c(0) is presented and the volume fraction of the phases estimated from the X-ray data. The presence of boron in the samples was confirmed by the inductive coupled plasma method. The microstructure of the samples was studied by scanning electron microscopy.