The influence of oxygen partial pressure and temperature on Bi-Pb-Sr-Ca-Cu-O 110 K superconductor phase formation and its stability

A systematic study of the influence of oxygen partial pressure on 110 K phase formation in the Bi-Pb-Sr-Ca-Cu-O system has been undertaken on the optimum nominal composition to promote the Bi2Sr2Ca2Cu3Ow (2223, 110 K) phase, i.e.; Bi1.84Pb0.34Sr1.91Ca2.03Cu3.06Ow. The relationship between 110 K phase fraction, oxygen partial pressure, sintering temperature, and time has been mapped for this composition via experimental data. The optimum conditions for 110 K phase formation were identified as 0.01≤PO2≤0.35 atm, at 820≤T≤880 °C for ≤36 h with intermediate grinding every 6 h. The single 110 K phase stability range was determined as PO2≤0.5 atm. The variation of oxygen partial pressure during the 110 K phase formation process was monitored via a Y2O3-ZrO2 oxygen sensor and a possible mechanism for its formation and the effect of PO2 thereon is discussed.