KINETICS AND FORMATION OF THE 110 K PHASE IN THE BISMUTH-LEAD-STRONTIUM-CALCIUM-COPPER-OXYGEN SYSTEM

The kinetics and formation of the 110 K superconducting phase in the B i-Pb-Sr-Ca-Cu-O system have been analyzed via Avrami theory, high-temp erature X-ray diffractometry, scanning and transmission electron micro scopy, and differential thermal analysis techniques, The kinetic study indicates that the reaction is diffusion controlled for oxygen partia l pressures of similar to 1-35 kPa (0.01-0.35 atm). The appearance of liquid increases the contact area of the reactant particles, thus acce lerating mass transport and the phase formation kinetics. The 110 K ph ase forms via reaction between the 80 K phase, secondary phases that a re rich in calcium and copper, and the liquid that contains lead, calc ium/strontium, and copper.