Synthesis of mercury cuprates

Mercury cuprates have very interesting potential applications that have not been thoroughly explored until now because of the complexity of their synt hesis. This paper presents an overview of recent results concerning their p rocessing. At first, a simple sol-gel technique is described that permits o ne to easily and intimately mix the precursors. The method uses the gelific ation of an inorganic solution of the cations by acrylamide polymerization. Mercuration of the precursor at moderate pressures (<2-5 MPa) is then disc ussed. The control of the total pressure during the synthesis by a simple m ethod is shown, and this enables one to quantify some important parameters of the synthesis and to optimize the superconducting properties. This metho d has been also used successfully to incorporate mercury into layers of pre cursors and then to form thick Layers of superconducting (Hg, Re)-1223, c-a xis oriented. Finally, mercuration at higher pressures (up to 6 GPa) is con sidered and the case of the double mercury layer Hg-2212 is discussed in co nnection with the oxygen content of the reactants.