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Y1.4.1

Solvothermal processes in Materials Synthesis Gérard Demazeau, Graziella Goglio and Alain Largeteau Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB-UPR.CNRS 9048) 87, Avenue du Docteur Albert Schweitzer, 33608 Pessac cedex, France. Ecole Nationale Supérieure de Chimie et de Physique de Bordeaux (ENSCPB) 16 Avenue Pey Berland, 33607 Pessac cedex, France. Université BORDEAUX 1 « Sciences and Technologies » 351 Cours de la Libération, 33405 Talence Cedex, France. ABSTRACT A solvothermal reaction can be described as a chemical reaction involving a solvent either in subcritical or supercritical conditions between different precursors. Such a solvent can act as a chemical component or a fluid phase able, through its physico-chemical properties, to induce the synthesis reactions. During the last fifteen years, solvothermal reactions have been used in different scientific areas involving basic or applied research. Several domains have been developed in Materials Chemistry: (i) the synthesis of novel materials, (ii) the development of new low temperature processes able to prepare functional materials, and in Materials Science: (i) new crystal growth processes, (ii) thin film deposition and (iii) sintering processes at low temperature. In Materials Chemistry three illustrations are described: (i) the synthesis through “geomimetism” of a new family of layered oxides: the phyllosiloxides, (ii) the synthesis of inorganic-organic materials, (iii) the potential of solvothermal processes for producing c-BN.

INTRODUCTION The synthesis of materials has always been an important task of scientists for basic or industrial applications. This scientific area roughly involves two main domains of activity: a) Materials Chemistry is related to (i) the synthesis of novel materials for improving either basic knowledge, in particular the correlations between composition, chemical bonding, structure and the resulting physical properties and (ii) new routes for producing materials, the main objective of the development of new processes is for economically cheaper industrial developments, b) Materials Science focuses on the optimisation of the shape of such materials (nano crystallites, thin films, single crystals…) for specific applications

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In Solid State Chemistry the high temperature route is the traditional way for the synthesis of novel materials. Due to the high cost of energy and the recent interest for original materials such as low temperature structural forms, inorganic- organic hybrids, open framework inorganic materials [1] low temperature processes have been developed. Solvothermal reactions appear a way for improving the accessibility to such materials and during these last fifteen years these reactions have been involved in two main domains: synthesis of novel materials and shaping processes of materials.

SOLVOTHERMAL REACTIONS - THE DIFFERENT INFLUENCING FACTORS AND THE DOMAINS OF APPLICATIONS Different factors governing the solvothermal reactions A solvothermal reaction can be roughly defined as a