Abstract:
We evaluated the microstructure, superconducting, and flux pinning properties of La-doped (Bi,Pb)-2212 bulk sample by varying its sintering temperature (T-sinter) between 846 degrees and 860 degrees C. Significant variations in microstructure, self- and in-field J(C)s at 64 K and flux pinning properties have been observed for La-substituted samples with respect to T-sinter. The sample sintered at 858 degrees C shows best self-field J(C) while that sintered at 846 degrees C shows the best in-field J(C) due to the changes in microstructure. The activation energy of flux motion (pinning potential U-o) is estimated from the field dependent resistivity-temperature curves, and the flux pinning force (F-P) from the field-dependent J(C) values. It is found that the La-doped samples, sintered at 846 degrees C show maximum F-P and U-o of 463 kN/m(3) and 0.380 +/- 0.001 eV as against 93.6 k/Nm(3) and 0.140 +/- 0.001 eV, respectively, for the sample sintered at 858 degrees C. The undoped (Bi,Pb)-2212 shows a maximum F-P and U-o of 12.7 k/Nm(3) and 0.074 +/- 0.001 eV, respectively. The origin of these enhanced properties is mainly from the normal-like defects introduced by optimum La-doping at the Sr-site, at an optimum sintering temperature
