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ABSTRACT Halogenoalkoxides are promising molecular precursors useable in sol-gel technology. They exhibit a lower sensitivity towards hydrolysis than common alkoxides and so appear to be easier to handle. Some data about the structure of titanium chloroalkoxides, pure and with the addition of a controlled amount of water, were obtained using FT-Raman, while the effect of thermal treatment under nitrogen or oxygen was studied using TGA-IR coupling. Finally the oxide products were characterized by Raman and by ED-XRMA, proving that chloroalkoxides could be used as molecular precursors of oxide by sol-gel process. We showed that TGA-FTIR coupling is a powerful tool in order to study a thermal treatment and could be used to optimize it. INTRODUCTION Numerous papers have reported the complexity of molecular precursors chemistry used in sol-gel process (mainly alkoxides) [1]. This intrinsic complexity of the metal alkoxide chemistry, which depends on many parameters (solvent, steric hindrance, concentration, temperature, nature of metals...), is increased when these species are mixed and hydrolyzed. Moreover, in order to control the hydrolysis rates of alkoxides (and so avoiding demixing phenomena) some organic additives have to be added. One of the most promising advantages of sol-gel technology is the possibility to obtain pure inorganic phases at low temperature allowing inorganic-organic devices to be built. The thermal treatment leading to the elimination of organic compounds (stabilizing agents, parent alcohol) appears to be a crucial step in order to control the macroscopic properties of the final materials. The control of the sol-gel process during all its steps by adaptable analytical technique remains an important challenge in order to insure a promising future for this technology in an industrial transfer. NIR excited Raman spectroscopy (FT-Raman) was used to characterize pure titanium chloroalkoxides and the products coming from their hydrolysis. The thermal treatment has been monitored by TGA-FTIR coupling.

These results have been correlated with Raman and ED-XRMA (Energy-dispersive Xray microscopy analysis) spectra of the final materials in order to control the nature

and the purity of the inorganic phases obtained.

655 Mat. Res. Soc. Symp. Proc. Vol. 346. 01994 Materials Research Society

EXPERIMENTAL All reactions were carried out under prepurified argon atmosphere at room temperature by using Schlenk techniques. Pure alkoxides and chlorides are from Aldrich. All solvents were appropriately dried, distilled prior to use and stored under argon. The IR and Raman spectra of the starting materials were recorded at a resolution of 4 cm-I on a FT-IR Bruker IFS66 spectrometer coupled with a TGA-50H Shimadzu. TGA were made under nitrogen or oxygen (rate=3°C/mn). The ED-XRMA spectra were recorded on Hitachi S570 Scanning Electron Microscope using Super Quantum Kevex Au-probe

(Crystal Si(Li)) with a 8 KeV excitation energy. The Raman spectra of the final materials

were recorded on a Raman spectrometer Dilor X