Solvothermal reactions: an original route for the synthesis of novel materials

Twenty years after the first development of solvothermal reactions, it appears important through the last research activities to trace the future trends taking into account their potentialities and the different economical constraints. During these last 20 years solvothermal reactions have been mainly used from preparing micro- or nanoparticles with different morphologies. Due to the importance to dispose of new materials for developing either basic research or industrial applications, such a presentation will be only focussed on the potentialities of solvothermal reactions in materials synthesis. Solvothermal reactions are mainly characterized by different chemical parameters (nature of the reagents and of the solvent) and thermodynamical parameters (in particular temperature, pressure). (a) The selection of the composition of the solvent opens new research areas for stabilizing materials belonging to different classes of materials (alloys, oxides, nitrides, sulphides). (b) The mild temperature conditions generally used are able to improve chemical diffusion and reactivity in order to help the preparation of specific materials at the frontier between either different classes of inorganic materials (oxides-nitrides, nitrides-halides) or inorganic/organic, inorganic/biologic frameworks. (c) The high pressure conditions, due to the small conveyed energy compared to temperature, allow also to stabilize metastable frontier materials (geo-inspired or bio-inspired materials). (d) In the future, taking into account, from one side: the economical and the environmental constraints, and from the other: the industrial demand of materials characterized by specific physical, chemical and biological properties, the potential developments of solvothermal processes will be analyzed.