Effect of Sintering Temperature on the Microstructural and Flux Pinning Characteristics of Bi_(1.6)Pb_(0.5)Sr_(1.8)La_(0.2)Ca_(1.1)Cu_(2.1)O_(8+δ) Ceramics

摘要

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° and 860℃. Significant variations in microstructure, self- and in-field J_Cs at 64 K and flux pinning properties have been observed for La-substituted samples with respect to T_(sinter). The sample sintered at 858℃ shows best self-field J_C while that sintered at 846℃ 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℃ 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℃. 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.