Preparation factor to enhance Jc (15,000 A/cm2) of Bi-2223 sintered bulk

Coprecipitate precursor was adopted in this experiment to facilitate synthesis in the calcination reaction. Coprecipitate powder was calcined on a silver base plate instead of an alumina plate. Al impurity content in the calcined powder decreased below 10 ppm, and 770 ppm of Ag was contained in the calcined powder. The calcined powder was pressed and then sintered at 850°C in the air with intermediate pressing by cold isostatic press (CIP) method. The critical current density (J_c) of the sintered bulk increased to be 15,000 A/cm ² with the three times of CIP and succeeding sintering. Adding Ag₂O to the coprecipitate deteriorated superconductivity of the sintered bulk. It is suggested that in the powder calcined on the Ag base plate Ag molecules evaporate from the plate, diffuse into the grain boundary, and finally improve the weak links during heat-treatment