Influences of oxygen content on the carrier concentration and transport properties of Bi-2212 bulks

Bi2.1Sr1.96Ca0.95Cu2.0O8 (Bi-2212) bulks have been obtained with Spark Plasma Sintering (SPS) method, with the precursor powders synthesized by co-precipitation process. Due to the vacuum environment involved in SPS, oxygen loss can be expected during sintering. Therefore, extra annealing processes under oxygen atmosphere were performed to enhance the superconducting properties of the bulks. Seebeck coefficient has been measured after different annealing process, in order to calculate the carrier concentration change with annealing process. The carrier concentration underwent a change from 0.178 to 0.198 per Cu ions after the 34 h annealing in oxygen at 773 K. The magnetic field dependence of critical current density, Jc, has been measured at 20 K on the samples with different annealing time. The critical current density increase from 550 to 5100 Acm-2 at zero field after the 34 h annealing, and the optimized Jc value can be obtained at the 34 h annealing sample over the entire magnetic field range.