Microstructure and transport properties of Bi1.6Pb0.5Sr2−xLuxCa1.1Cu2.1O8+δ superconductor

The microstructure and electrical properties of the rare-earth Lu doped (Bi, Pb)-2212 superconductor have been investigated. The Lu concentration is varied from x = 0.000 to 0.150 in a general stoichiometry of Bi1.6Pb0.5Sr2−xLuxCa1.1Cu2.1O8+δ. The X-ray diffractometer and energy dispersive X-ray spectroscopy analyses show that Lu atoms are successfully substituted into the (Bi, Pb)-2212 system and they induce significant changes in the microstructure, hole concentration, critical temperature, self- and in-field critical current density of the system. The flux pinning force (FP) calculated from the field dependant JC values shows that the irreversibility lines (IL) of the Lu substituted (Bi, Pb)-2212 shift towards higher fields to different extents depending on the Lu stoichiometry. The samples with x = 0.100 show a maximum FP of 1395 ± 1 × 103 N m−3 as against 30 ± 1 × 103 N m−3 for the pure sample. The changes in hole concentration followed by very high enhancement of critical temperature (TC), self-field JC, JC(B) characteristics and FP due to Lu substitution are of great scientific and technological significance and the results are explained on the basis of microstructural variation with respect to Lu stoichiometry, hole optimization and formation of point defects due to the doping of Lu atoms in Bi1.6Pb0.5Sr2−xLuxCa1.1Cu2.1O8+δ system.