DIRECT SYNTHESIS OF BI-2212 BY THERMAL-DECOMPOSITION OF SALT PRECURSORS

Thermal decomposition of freeze-dried nitrate precursors with cation r atio Bi:Pb:Sr:Ca:Cu = 1.8:0.4:2:2:3 resulted in formation of the Bi-22 12 phase within 10 min of thermal treatment at 860 degrees C. The key features of the process are fast heating rate during decomposition, hi gh chemical homogeneity of precursor, and prevention of melting of the copper nitrate by additional thermal dehydration at 100-120 degrees C , The reactivity of the (Bi,Pb)-2223 precursor obtained this way can b e further enhanced by heat treatment at reduced P(O-2). Analysis of th e processes occurring during this treatment shows that the redistribut ion of Pb between eutectic mixtures of cuprates and (Bi,Pb)-2212 is a possible reason for reactivity enhancement.