Growth Process of the (2223) Phase in Pb-Added Bi-Sr-Ca-Cu-O

Abstract

The growth process of the (2223) phase in Bi-Sr-Ca-Cu-O has been studied for oxides with nominal composition Bi2Pb0.6Sr2Ca2Cu3O x prepared by sintering at 835∼855°C for 5∼160 h in air. The partial melting which starts to occur at T pm≃842°C enhances the growth rate of the (2223) phase and produces a nearly single phase within 40 h. However, it causes a disturbance in current paths and suppresses the value of T c(ρ=0) below 100 K. The sample which has the highest T c(ρ=0) and the nearly single (2223) phase is obtained by sintering at a temperature just below T pm for a long period of time.

Phase development and critical current density of Bi-2223 tapes fabricated by groove rolling

“…The Bi-2223 tapes were heat treated at temperatures of 840 • C which is close to the formation of the liquid phase. According to Oota et al [27] the liquid phase is formed as a result of a eutectic reaction between 2201 and Ca 2 PbO 4 . The liquid phase helps to heal microcracks induced during the thermomechanical treatment stages.…”

The powder-in-tube processing and properties of Bi-2223

“…This is possible because of the existence of a region of solid solubility between the cations in this system. 21 Oote et al 23 showed that with a suitable heat treatment, an appropriate excess of calcium and copper can accelerate formation of the 2223 phase. Figure 1 shows the sensitivity of the Ca / Cu cation contents to heat-treatment times at 830-840°C in air.…”

Fabrication and Characterization of High- TcSuperconducting Continuous-Tube-Forming/Filling Bi(Pb)-2223/Ag Composites and Coils

“…Various authors have reported that the reaction corresponding to the DTA peak 344 just before melting occurs seems to be a necessary condition for growth of the 2223 phase (22)(23)(24). The region containing a liquidphase is often referredto as the region of partial melting, which can cover a temperature range of up to -30°C, beginning at the onset of melting temperature, as reported by Yamada et al …”

“…(25). The favorable sintering temperature (T) for 2223 phase formation for precursor powders has also been shown to be bounded between the endothermic partial melting peak (T pm ) and the maximum peak at which melting occurs (T m ) , obtainable from DTA curves (22,24,26). Figures 7 and 8 show respectively the DTA curves obtained for the five different precursor powders and two composites of Bi(Pb)-2223.…”