TOWARD MOLECULAR DESIGN OF HOMOMETALLIC AND HETEROMETALLIC PRECURSORSFOR LANTHANIDE-BASED OXIDE MATERIALS

Lanthanides are involved in a variety of advanced oxides and non-oxide materials. Chemical routes (sol-gel and MOCVD) offer more flexibility than traditional solid-state synthesis, in terms of control of parame ters, microstructure and shapes, but they rely on the availability of the appropriate homo- or heterometallic precursors. Metal alkoxides an d beta-diketonates are presently the most attractive molecular precurs ors to oxides. Synthetic routes and strategies (choice of OR and/or an cillary ligands) to control the properties (solubility, hydrolysis rat es and volatility) are reviewed. The specificity of rare earth metals, their large size and oxophilicity, results in quite diverse alkoxide aggregates for common OR ligands, such as isopropoxide, t-butoxide or 2-methoxyethoxide, as established by their characterization in the sol id state. Strategies for elaboration of mixed-metal species and for a control of the stoichiometry between the metals are discussed. Hydroly sis-polycondensation reactions of the mixed-metal species have been es timated. Examples of implications of lanthanide alkoxides in materials science are given.