SYNTHESIS AND CHARACTERIZATION OF 110K SUPERCONDUCTING PHASE IN BI(PB)-SR-CA-CU-OXIDE

The temperatures and sequence of formation of superconducting phases within the composition Bi1.6Pb0.4Sr2Ca2Cu4Ox were determined using simultaneous differential thermal analysis (DTA) and thermogravimetric analysis (TGA), X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). A single phase high-Tc ceramic was obtained by a solid state reaction using predetermined firing conditions, although a transmission electron microscopy (TEM) study showed a small amount of glass phase in the grain boundary tripoint regions. The unit cell of the high-Tc phase was refined as a=0.5413 nm, b=0.5414 nm, c=3.715 nm. The melting temperature of the high-Tc phase is in the region of 852-862°C. The effect of lead was believed to lower the temperature of formation of the high-Tc phase. Lead was also found to evaporate from the matrix during and after high-Tc phase formation, whereas bismuth was found to be stable in both the low-Tc phase and high-Tc phase compounds. © 1990 Chapman and Hall Ltd.