The influence of heat treatment on the microstructure, flux pinning and magnetic properties of bulk BSCCO samples prepared by sol-gel route

We study the combined influence of calcination and sintering temperature on the microstructure, superconducting and pinning properties of Bi1.6Pb0.4Sr2Ca2Cu3O10+theta (Bi-2223) prepared by the sol-gel route. Using several characterization techniques, including X-rays diffractometry and electrical transport measurements, we find that the powders calcined at 820 degrees C often result in a crystal higher critical current density (J(c)) compared those calcined at 830 degrees C. The powder calcined at 820 degrees C and sintered at 850 C (Bi-2223(820)(850)) showed the best grain morphology and the largest magnetic hysteresis loop and a J(c) equal to 12.94 x 10(5) A/cm(2), comparable to the best results found in the literature for Bi-2223. The enhancement in J(c) for Bi-2223(820)(850) seems to be due to improved grain structure rather than creation of effective pinning centers, because the scaling behavior of flux pinning force densities indicates that the main pinning mechanism for all samples is normal point pinning.