Comparison of solid-state reaction and modified citrate process for Bi-2212 ceramics synthesis

Bi2Sr2CaCu2O8+d (Bi-2212) superconductive ceramics powders were prepared using a modified citrate process which consists in forming powders from a gel. The obtained powders were characterised by X-ray diffraction and scanning electronic microscopy in order to determine their phase purity and their microstructure. Dilatometric tests have been carried out to study the sintering behaviour. The magnetic and resistivity curves of the investigated compositions will be also discussed. The obtained results were systematically confronted with the ones obtained from powders synthesized by the conventional solid-state reaction in the same conditions of temperature and calcination time. It has been found that the densification of Bi-2212 is very weak during sintering whatever the synthesis process. In both cases the critical temperature was determined approximately at 80 K but the comparison shows that the modified citrate process is an interesting way of elaboration in terms of purity, homogeneity and synthesis time.