High Pressure Thermodynamic Investigations on the Bi-Pb-Sr-Ca-Cu-O system

The lack of thermodynamic information concerning the Bi,Pb(2223)-liquid equ ilibrium has not made possible, so far, to find any equilibrium formation r oute. The formation of Bi,Pb(2223) occurs via a non-equilibrium route, the grains growing from the local transient liquid. One of the main difficultie s in solving the phase diagram at high temperature arises from an uncontrol led loss of some volatile elements and oxides, We have undertaken the inves tigation of the phase diagram at high pressure. A new prototype of High-Pre ssure DTA was built, operating up to 150 bar, and a dedicated High Isostati c Pressure furnace (up to 1 kbar, p(O-2)=0.2 bar) was used to anneal the sa mples 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.