Influence of sintering temperature on microstructure, critical current density and pinning potential of superconducting Bi1.6Pb0.5Sr1.8Dy0.2Ca1.1Cu2.1O8+δ ceramics

The influence of sintering temperature on the microstructure, critical current density (JC), pinning potential values (U0) and flux pinning properties of Bi1.6Pb0.5Sr1.8Dy0.2Ca1.1Cu2.1O8+δ superconductor has been investigated. The samples are prepared by the solid-state route and sintered at temperatures ranging from 846 to 860 °C. A systematic correlation between the sintering temperature, Lotgering index, JC, U0 and flux pinning properties has been found. The samples sintered at lower sintering temperature (846 °C) have more grain boundaries with smaller grains while those sintered at a higher temperature (856 °C) contain larger grains with good texturing. The flux pinning force (FP) calculated from the field dependent JC values shows that the irreversibility lines (IL) of the Dy-doped samples shift towards higher fields to different extents depending on the sintering temperature. The maximum value of FP = 1697 kN m−3 is obtained for the sample sintered at 846 °C and the peak position of FP is obtained at 0.96 T as against 616 kN m−3 and 0.52 T for the sample sintered at 856 °C. The U0 values calculated by Anderson's function is maximum for the sample sintered at 846 °C. But the self-field JC value of this sample is lower than that of the samples sintered at 856 °C. The samples sintered at 856 °C show best self-field JC due to the improved microstructure. The changes in microstructure followed by very high enhancement of self-field JC, JC(B) characteristics, FP and U0 values within a narrow temperature range, are of great scientific and technological significance and the results are explained on the basis of microstructural variation with respect to sintering temperature, hole optimization and formation of point defects due to the doping of Dy atoms in Bi1.6Pb0.5Sr1.8Dy0.2Ca1.1Cu2.1O8+δ system.

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