THE EFFECTS OF THE SINTERING SCHEDULE ON THE SUPERCONDUCTING PROPERTIES OF BI(PB)-SR-CA-CU-O THICK-FILMS

Superconducting Bi(Pb)-Sr-Ca-Cu-O powders were prepared by the emulsion drying method. The powders consisting of low-T(c) phase (Bi(Pb)2Sr2Ca1Cu2Oy) and a small amount of Ca2PbO4 were prepared by calcining in low oxygen partial pressure at 800-degrees-C. Bi(Pb)-Sr-Ca-Cu-O thick films on single crystal MgO(100) substrates were fabricated with the calcined powder using a screen-printing technique to study the effect of the sintering schedule on the superconducting phase formation and properties. The films sintered at 830-degree-C consisted of the mixture of the low-T(c) phase and the high-T(c) phase even though the sintering was done over 90 h (normal sintering). The high-T(c) phase was formed quickly in the films sintered with a step sintering schedule, sintering at 840-degrees-C for 4 h and at 830-degrees-C for 30 h, and the best film showed a sharp superconducting transition at above 105 K. The low-T(c) phase was formed in the partial melting process, that is, sintering at 850-degrees-C for 1 h and slowly cooling to 830-degrees-C, and the low-T(c) phase grains were highly textured. The film showed zero resistance at 75 K and the critical-current density of this film was about 2500 A cm-2 at 25 K.