FORMATION OF SUPERCONDUCTING PHASES IN A MECHANOCHEMICALLY ACTIVATED BI-SR-CA-CU-O SYSTEM

It is revealed that the degree and type of the mechanochemical activat ion effect on the synthesis and formation mechanism of Bi-containing h igh-temperature superconductors (HTSC) of the 2212 and 2223 compositio n differ substantially from that observed in synthesis of YBa2Cu3Ox. M echanochemical activation is shown to affect the kinetics of solid-pha se interaction and alter the order of entering into the reaction of th e mixture components changing their reactivity and, in the final run, the mechanism of formation of Bi-Sr-Ca-Cu-O compounds. As a result, th e most favorable conditions arise for formation of the 2201 phase. For mation of compounds 2212 and 2223 can either be substantially promoted or, on the contrary, inhibited, depending on the precursor choice. It is supposed that the reaction should necessarily include the liquid p hase (in microscopic amounts) in order HTSC compounds to form in this system and that the mechanism of their formation under mechanical impa ct is of the intercalation type. Magnetic studies of compound 2212 pre pared under different conditions revealed a number of peculiarities of the field dependence of magnetization which suggest the cluster natur e of the superconducting Bi-containing phase.