FAST SYNTHESIS OF SINGLE-PHASED 110-K BISMUTH SUPERCONDUCTOR BY FREEZE-DRYING OF ACETIC PRECURSORS - KINETIC ROLE OF CALCIUM AND COPPER OXIDES

Although the usefulness of solution procedures to improve the synthesi s of bismuth HTSC has been argued, an adequate control of the procedur al variables has allowed us to isolate the 110 K phase as the only sup erconducting phase after such a short sintering time as 22 h. The prec ursors used have been freeze-dried powders resulting from acetic solut ions containing excess Ca and Cu. TGA-DTA and XRD experiments have bee n performed to follow the subsequent solid-state reaction processes. T he initial formation of a mixed bismuth-lead oxoacetate, as intermedia te to (Bi1-yPby)2Pby)2CuO4, and the presence of an excess of Ca2CuO3 i n the last reaction step are two of the main factors driving the fast synthesis of the 110 K phase.