High pressure thermodynamic investigations on the Bi-Pb-Sr-Ca-Cu-O system

The lack of thermodynamic information concerning the Bi,Pb(2223)-liquid equilibrium has not made it possible, so far, to find any equilibrium formation route. The formation of Bi,Pb(2223) occurs via a non-equilibrium route, the grains growing from the local transient liquid. One of the main difficulties in solving the phase diagram at high temperature arises from an uncontrolled loss of some volatile elements and oxides. We have undertaken the investigation of the phase diagram at high pressure. A new prototype of High-Pressure DTA was built, operating up to 150 bar, and a dedicated High Isostatic Pressure furnace (up to 1 kbar, p(O/sub 2/)=0.2 bar) was used to anneal the samples without mass losses. We report on the effect of pressure on the Bi,Pb(2223) formation and decomposition, and on the influence of oxygen partial pressure under these conditions.