Abstract:
The effect of substitution of the rare earth Dy on the critical current density and flux-pinning properties of (Bi, Pb)-2212 system prepared by a solid-state synthesis in bulk polycrystalline form was studied. Phase analysis, microstructural investigation, and superconducting characterization were performed to evaluate the relative performance of the samples. The XRD and EDS analyses show that Dy atoms are successfully substituted in place of Sr in the system. The critical temperature (T(C)), critical current density (J(C)), and field dependence of J(C) of the Dy-substituted samples are found to be highly enhanced for optimum doping levels. The flux-pinning force (F(P)) calculated from the field-dependent J(C) values shows that the irreversibility lines (IL) of the Dy-substituted (Bi, Pb)-2212 shift toward higher fields to different extents depending on the value of Dy stoichiometry (x). The samples with x=0.2 show a maximum F(P) of 135.1 x 10(4) N/m(3) and the peak position of F(P) shifts to higher fields (0.80 T) as against 2.0 x 10(4) N/m(3) and 0.12 T for the pure sample. Also, the values of the self-field J(C) and pinning potential (U(0)) are maximum for this sample (x=0.2). The enhancements of J(C)(B) characteristics, and the values of U(0) and F(P) are explained on the basis of the hole optimization and formation of point defects due to the substitution of Dy into the (Bi, Pb)-2212 system.
