Enhancement of flux pinning and Anderson-Dew-Hughes pinning analysis in Bi1.6Pb0.5Sr2−x TbxCa1.1Cu2.1O8+δ superconductor

The effect of substitution of rare-earth (RE), Tb on the critical current density (JC), pinning potential (U0) and flux pinning properties of (Bi,Pb)-2212 superconductor was studied. The XRD and EDS analyses show that Tb-atoms are successfully substituted into the (Bi,Pb)-2212 system. The critical temperature (TC), self-and in-field JC of Tb-substituted samples are found to be highly enhanced for optimum doping levels. The sample with x = 0.075 shows the maximum flux pinning force (FP) of 275 × 104 N m−3 and the peak position of FP shifts to higher fields (0.84 T) as against 3.0 × 104 N m−3 and 0.12 T for the pure-sample. In addition, the values of self-field JC and U0, calculated using Anderson's function are maximum for this sample (x = 0.075). The Dew-Hughes pinning analysis shows that the main pinning mechanism is due to the point-defects brought about by the substitution of Tb-atoms at the Sr-site. The enhancements in JC(B) characteristics, values of U0, irreversibility field (Birr) and FP are of great scientific and technological significance and are explained on the basis of hole optimization and formation of point-defects due to the substitution of Tb at Sr-site of (Bi,Pb)-2212 system.