The influence of sintering temperature on the microstructure and superconducting properties of Bi1.7Pb0.4Sr1.8Nd0.2Ca1.1Cu2.1O8+δ superconductor

The effect of sintering temperature on the microstructure and superconducting properties of Bi1.7Pb0.4Sr1.8Nd0.2Ca1.1Cu2.1O8+delta has been investigated. The samples are prepared by the solid-state route. Remarkable variations in microstructure, critical current density (J(C)) and flux pinning properties have been observed for Nd-substituted samples, sintered at different temperatures in the range 846-852 degrees C. The flux pinning force (F-P) calculated from the field-dependent J(C) values show that the irreversibility lines (IL) of Nd-substituted samples shift towards higher fields to different extents depending on the sintering temperature. The samples sintered at 846 degrees C show maximum flux pinning force (F-P) of 631 kN m(-3) and the peak position of F-P shifts to higher fields (0.8 T) as against 262 kN m(-3) and 0.44 T for the samples sintered at 852 degrees C and 18 kN m(-3) and 0.08 T for the undoped sample sintered at its optimum sintering temperature, respectively. But the self-field J(C) value of the samples sintered at 846 degrees C is lower than that of the samples sintered at 852 degrees C. The samples sintered at 852 degrees C show maximum self-field J(C) due to improved microstructure. The changes in microstructure followed by very high enhancement of self-field J(C), J(C)-B characteristic and pinning force density (F-P) due to Nd substitution within a narrow temperature range, is of great scientific and technological significance.