STRUCTURAL AND FTIR SPECTROSCOPIC STUDIES OF GEL-XEROGEL-OXIDE TRANSITIONS OF SNO2 AND SNO2-SB POWDERS AND DIP-COATED FILMS PREPARED VIA INORGANIC SOL-GEL ROUTE

Sb doped and undoped SnO2 thin solid coatings were prepared by the dip -coating technique via the sol-gel route. Aqueous gels of undoped comp ound were made by using a SnCl4 precursor and doping was achieved thro ugh the addition of SbCl3 in the concentration range 1-10 mol%. Fourie r transform infrared (FTIR), ATR and near normal reflectance spectrosc opic techniques were utilized to determine the vibrational spectra of aqueous gels, xerogels and oxides of Sb doped and undoped compounds. A nalysis of the corresponding FTIR spectra revealed the existence of Sb -O modes at 770 cm(-1). The drying of both types of gel was accompanie d by the formation of hydrogen bonds of medium strength with the OH-O length about 2.7-2.8 Angstrom. Some properties of pure and Sb doped ox ide powders formed in the temperature range less than or equal to 1000 degrees C were measured by thermogravimetry, X-ray diffraction and FT IR spectroscopic techniques. The doping brought about a broadening of the X-ray diffraction peaks. The reflectivity of the samples increased in the spectral range 4000-600 cm(-1) up to 60%, due to the formation of plasma modes. Thin solid films were made by the dip-coating method . The efficiency of the dip-coating process was 0.02-0.1 mu m per dipp ing, depending on the viscosity of the gel. The electrical resistivity of the doped SnO2 coatings was about 1.2 x 10(-2) Ohm cm and thus com parable to the electrical resistivity of the alkoxide derived Sb doped SnO2. Doping decreased visible transmittance similar to 5% but infrar ed reflectance increased up to 40%, depending on the film thickness.