Composites formed by combinations of polyethylene oxide (PEO) and sodium trifluoroacetate (CF3COONa) with different aluminum oxide (Al2O3 ) concentrations were synthetized. Infrared (IR), Raman spectroscopy, X ray diffraction (XRD) and atomic force microscopy (AFM) analyses, were performed to characterize the composites. Changes on the XRD intensity peaks, and variations in intensity and position of some peaks in Raman and IR spectroscopy were observed for different concentrations of added Al2O3 . The decrease in the XRD peaks of the PEO when it is combined with the salt, revealed that crystallinity in polymer was reduced, being lower when the alumina is added. The increase in roughness root medium square (R RMS ) observed by AFM when Al2O3 was added, agree with reduction in crystallinity observed with XRD studies. Changes in the structure of PEO showed in the absorption lines IR and Raman, due to addition of CF3COONa salt and Al2O3 filler, have been attributed to the interactions between the electrolyte and the filler.&nbsp