In situ study of the synthesis of Hg2Ba2YCu2O8-delta at high pressure and high temperature by x-ray synchrotron diffraction

In this experiment we investigated the synthesis of the double mercury laye r compound Hg2Ba2YCu2O8-delta (Hg-2212) at 4 GPa and 900 degrees C by in si tu x-ray diffraction performed at the high-pressure ID30 beam line at ESRF The chemical path observed depends on the choice of the initial mixture. If one starts from a mixture of oxides and copper, an intermediate oxide phas e (a high-pressure variety) containing barium and mercury is formed (we do not know if copper is present). This intermediate phase is then converted i nto the final Hg-2212 product. On the other hand, Hg-2212 grows directly fr om a pre-reacted precursor 'Ba2YCu2Oy' mixed with HgO. This in situ techniq ue clearly shows its efficiency in identifying, in real time, a phase that would have been difficult to observe ex situ.