P. Toulemonde et al., Intermediate phase formation during Hg-2212 synthesis by in-situ X-ray synchrotron diffraction, PHYSICA C, 341, 2000, pp. 2457-2458
The synthesis of Hg2Ba2YCu2O8-delta (Hg-2212) requires a high pressure - hi
gh temperature process. The determination of the reaction path is an import
ant piece of information for its optimization. In-situ X-ray diffraction at
high pressure-high temperature has been performed tot monitor this process
by using the synchrotron source of ESRF (Grenoble-France, ID30 beam line).
The synthesis was followed at 4 GPa from room temperature to 850 degreesC.
When the starting powder is a mixture of oxides (BaO2, YzO(3), CuO) and Cu,
a transient oxide phase composed at least of Pa and Hg is formed that is t
hen converted into the final Hg-2212 product. Conversely no intermediate ph
ase can be detected when a pre-reacted precursor "Ba(2)YCu(2)Oy" mixed with
HgO is used.