Characterization of Bi1.6Pb0.4Sr2Ca2Cu3Oy ceramic superconductor prepared via coprecipitation method at different sintering time

The Bi(Pb)-2223 superconductor has been prepared via coprecipitation (COP) method from solutions of metal acetates and 2-propanol solution of oxalic acid at low temperature (0-2 degrees C). The metal oxalates powder was subjected to precalcination of 12 h at 730 degrees C, followed by 24 h calcination at 845 degrees C. The pelletized powder was sintered for 24, 48 and 100 h at 850 degrees C. The dominance of high-T-C phase was observed for all samples as evidenced in the single step transition of (R-T) curves. The T-C(R = 0) for samples sintered at 24, 48 and 100 h were 102, 102 and 104 K, respectively. XRD data showed the tetragonal structure for all samples followed by the enhancement of the 2223 phase as sintering time increased. Ac magnetic susceptibility measurements showed the improvement of the grain connectivity as sintering time increased. SEM micrographs showed large flaky grains of similar to 7 mu m in size and randomly distributed, which belong to 2223 phase. The degree of grains alignment increased as the sintering time increased.