Effect of Oxygen Partial Pressure on the Microstructure and Formation of Bi-2223 Phase in the Partial-melting and Sintering Process

The effect of oxygen partial pressure on the microstructure and formation of the (Bi,Pb)-2223 phase in the partial-melting and sintering process was studied. Samples with two nominal compositions Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Oy and Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy were prepared by following sintering conditions after partially melted at 875 °C for 1 h in air: (i) 760 ºC for 120 h in N2, (ii) 825 °C for 120 h in 8% O2+N2, (iii) 840 ºC for 120 h in air and (iv) 845 °C for 120 h in O2. In the samples sintered in pure N2 and in pure O2, the Bi-2212 phase as a major phase exists without the Bi-2223 phase. The Bi-2223 phase appears in the samples sintered in air and in 8% O2+N2, and the highest fraction of the Bi-2223 phase appears in the sample with the composition of Bi1.8Pb0.4Sr1.9Ca2.1Cu3.5Oy sintered in 8% O2+N2.