Microstructural and superconducting properties of Yb-substituted (Bi,Pb)-2212 superconductor sintered at different temperatures

The influence of sintering temperature on the microstructure and superconducting properties of Bi1.7Pb0.4Sr1.8Yb0.2Ca1.1Cu2.1O8+δ has been investigated. Yb-free (Bi1.7Pb0.4Sr2.0Ca1.1Cu2.1O8+δ) and Yb-substituted (Bi1.7Pb0.4Sr1.8Yb0.2Ca1.1Cu2.1O8+δ) superconducting samples are prepared by solid-state synthesis in bulk form. Significant variations in microstructure, critical current density (JC) and flux pinning properties have been observed for Yb-substituted samples, sintered at different temperatures in the range 846-852 °C. The flux pinning force (FP) calculated from the field dependant JC values show that the irreversibility lines (ILs) of Yb-substituted samples shift towards higher fields to different extents depending on the sintering temperature. The samples sintered at 846 °C show maximum flux pinning force of 896 kN m−3 and the peak position of FP shifts to higher fields (0.92 T) as against 16 kN m−3 and 0.12 T for the undoped sample sintered at 848 °C. But the self-field JC value of the samples sintered at 846 °C is lower than that of the samples sintered at 852 °C, which show the maximum self-field JC due to improved microstructure. The variation in microstructure followed by very high enhancement of self-field JC, JC-B characteristic and pinning force density due to Yb substitution within a narrow temperature range is of great technological relevance.