Objective
Simple and bi-metallic alkoxides are part of a vast family of organo-metallic molecules used as volatile metal carriers or as precursors for the preparation of oxides by the sol-gel process. This is a fast developing area of materials chemistry in view of the great number of applications for glassy or crystalline simple or mixed oxides in optics, electronics, catalysis, superconductors. This unique class of compounds offers many advantages over the conventional methods of access to mixed oxides with designed properties, among which are spectral control of the high purity of the precursors giving the highest purity oxides, high precision in the stoichiometry in doped or mixed phases, the possibility of the accurate design of the macroscopic properties of the generated solids in the form of powders, thin layers or crystallites.
In the field of fundamental chemistry, many problems remain unsolved due to the structural complexity of the molecular solutions of the precursors which are monomeric in a few exceptional cases but generally appear as oligomers or polymers and undergo several interconversions by thermal treatment or ageing of the solutions. These effects of co-ordination polymerism have to be characterised in the case of bi-metallic mixtures to allow their safe use to prepare designed mixed oxides. Recent progress has been realised by the Russian teams in the electrochemical synthesis of many alkoxides giving better yields and purity than the multistep chemical way of preparation classically used.
This programme aims at improving and extending the knowledge in both areas. The next steps of transformation of the precursor solutions into oxides imply a good monitoring of an hydrolysis stage and of a condensation stage in which many factors act simultaneously. This area of the research still needs to be investigated, both in terms of practical data collection on an extended array of examples, and in the fundamental approach to obtaining good models of the gel formation and thermal condensation reactions. The nature, local microstructure, bulk macrostructure and properties of the final oxide depend on the growth process. The second goal of this programme is to extend knowledge in this area.
Many syntheses of mixed systems with different alkoxy groups will be done or are already in progress with: Mg,Sr,Ba,Cu,rare earths, Ti, Zr,Hf, V, Ta, Mo, W derivatives. Alterations of the properties during isolation, treatment and storage of the mixed phases will be explored by physical methods. One approach to optimise the controlled synthesis of bi-metallic alkoxides is to establish the tri-component solubility diagrams M(OR)n-M'(OR)n' -Solv. The network of laboratories provides complementary expertise to study the precursor solutions, the process of hydrolysis and thermal treatment and the characterisation of the properties of the final oxides as well as of the intermediate compounds.
Call for proposal
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13397 Marseille
France