XANES observations of the inhibition and promotion of anatase and rutile phases in silver containing films

X-ray absorption near-edge structure (XANES) spectroscopy has been applied to characterize the phase evolution of Ag-TiO2 films subjected to annealing treatments up to 1000 degrees C. Silver has been theoretically predicted as a rutile promoter in anatase powders lowering the transition temperature, however, no systematic studies on films have been reported yet. In this work, the Ti L-2,L-3- and O K-edge in XANES spectra were used as fingerprints of the phase structure of the films. The results show that silver atoms strongly affect the transition of the initially amorphous films to the anatase structure, delaying the crystallization temperature up to 400 degrees C and, at the same time, promoting the subsequent phase transformation from anatase to rutile at temperatures as low as 600 degrees C. These results have been confirmed by X-Ray Diffraction (XRD) analysis as well as by High Resolution TEM images (HRTEM) of films.