  The decomposition and the reformation of the (Bi,Pb)2Sr2Ca2Cu3O10+d
(?Bi,Pb(2223)?) phase have been investigated in-situ by means of
High-Temperature Neutron Diffraction, both in sintered bulk samples and in
Ag-sheathed monofilamentary tapes. Several decomposition experiments were
performed at various temperatures and under various annealing atmospheres,
under flowing gas as well as in sealed tubes, in order to study the appropriate
conditions for Bi,Pb(2223) formation from the melt. The Bi,Pb(2223) phase was
found to melt incongruently into (Ca,Sr)2CuO3, (Sr,Ca)14Cu24O41 and a
Pb,Bi-rich liquid phase. Phase reformation after melting was successfully
obtained both in bulk samples and Ag-sheathed tapes. The possibility of
crystallising the Bi,Pb(2223) phase from the melt was found to be extremely
sensitive to the temperature and strongly dependent on the Pb losses. The study
of the mass losses due to Pb evaporation was complemented by thermogravimetric
analysis which proved that Pb losses are responsible for moving away from
equilibrium and therefore hinder the reformation of the Bi,Pb(2223) phase from
the melt. Thanks to the full pattern profile refinement, a quantitative phase
analysis was carried out as a function of time and temperature and the role of
the secondary phases was investigated. Lattice distortions and/or transitions
were found to occur at high temperature in Bi,Pb(2223), Bi,Pb(2212),
(Ca,Sr)2CuO3 and (Sr,Ca)14Cu24O41, due to cation diffusion and stoichiometry
changes. The results indicate that it is possible to form the Bi,Pb(2223) phase
from a liquid close to equilibrium conditions, like Bi(2212) and Bi(2201), and
open new unexplored perspectives for high-quality Ag-sheathed Bi,Pb(2223) tape
processing.
