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TUTORIAL


Toward molecular design of oxide precursors for advanced materials

Liliane G. Hubert-Pfalzgraf
IRC, Université de Lyon1 - 69626 Villeurbanne Cedex (France)

 

CONCLUSIONS

Among the various precursors of metal oxides namely metal b-diketonates and metal carboxylates, metal alkoxides are the most versatile. They are available for nearly all elements and cost-effective synthesis from cheap feedstoks have been developed for some. The selection of appropriate OR groups -bulky, functional, fluorinated (ORf) allows to tune their properties. A large range of mixed-metal compositions is accessible in mild conditions, often at RT, by mixing metal alkoxides (or oxoalkoxides) and other oxide precursors. Well-defined "single-source" precursors of MTiO3 (M = Pb, Ba, Sr) for instance are known. The choice of an OR group, of an other ligand, acetate or b-diketonate, is not innocent for getting precursors having the right stoichiometry between the metals by Lewis acid-base reactions. One can notice the importance of the oxo ligand due to the versatility of its coordination modes and it can be essential for reactivity. The various ligands play an important role for transformation into materials which remains to be better understood.

For elements others than silicon and tin, precursors bearing functionalities require linkage to the metal via oxygen atoms (O-donor ligands). Compounds with polymerizable sites accessible for copolymerization are available for some metals (Ti, Zr, Nb, Ln) as well as for some mixed-metal (Ti-Zr) species. Metal alkoxides represent also a potential for materials beyond oxides, such as phosphates or sulfides.

Functional metal carboxylates have been developed in order to overcome solubility hurdles. They can represent alternatives to metal alkoxides if formation of stable carbonates, a favoured decomposition pathway for such ligands, does not preclude low temperature crystallisation.

 

 

 
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