Sol-gel synthesis of humidity-sensitive P2O5-SiO2 amorphous films

The sol-gel synthesis of silicophosphate gels using phosphoryl chloride and tetraethoxysilane as molecular precursors is reported and discussed. Gel-d erived glasses and films having the molar compositions 10P(2)O(5) . 90SiO(2 ) and 30P(2)O(5) . 70SiO(2) have been obtained. The structure of the dried gels as well as the structural modifications that occurs during the transfo rmations in gel-derived glasses are analyzed by Fourier transform infrared spectroscopy (FTIR). It has been found that the evidence of the P-O-Si link ages begins to appear only on the FTIR spectra of the bulk gels heat treate d up to 400 degrees C while they are well resolved on the FTIR spectra of t he bulk gel samples heated up to 1000 degrees C indicating that at this tem perature the transformation in the corresponding gel-derived glasses occurs . The humidity sensitive properties of the gel-films have been evaluated by electrochemical impedance spectroscopy (EIS). The phosphorous content as w ell as the temperature of the heat treatments strongly affect the sensitivi ty to RH of the gel-derived films.