EFFECT OF CONSTITUENT CONTENTS ON THE FORMATION AND MICROSTRUCTURE OF(BI, PB)-2223 PHASE IN PARTIAL-MELTING AND SINTERING PROCESS

The influence of Bi, Sr, Ca and Cu contents on the formation and micro structure of the (Bi, Pb)-2223 phase in Bi1.6+bPb0.4Sr2-alphaCa2+alpha Cu3+cOy, in the sintering process at 1113 K after partial melting at 1 148 K for 1 h, was studied. The compositions which are slightly defici ent in Sr and richer in Bi, Ca and Cu are favorable for the formation of the 2223 phase, and the optimum composition for the preparation of (Bi, Pb)-2223 phase is Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy. The high-temperatu re microstructure held at 1148 K for 1 h mainly consisted of (Sr, Ca)( 2)CuO3, (Sr, Ca)CuO2 and a liquid phase. However, with increasing Cu c ontent, the relative amount of (Sr, Ca)CuO2 increased and that of (Sr, Ca)(2)CuO3 decreased. The microstructure with equal amounts of (Sr, C a)CuO2 and (Sr, Ca)(2)CuO3 prior to sintering is favorable for the for mation of the (Bi, Pb)-2223 phase. A lot of the particle-like inclusio ns Sr3PbOx precipitated in the samples with the Sr-rich and Ca-deficie nt composition during the sintering process after the partial-melting. It is suggested that the precipitation of Sr3PbOx in large amounts in the Sr-rich and Ca-deficient samples results in a decrease of Pb cont ent in (Bi, Pb)-2212 phase, thus slowing the formation-rate of the 222 3 phase from the 2212 phase.