An XPS study of iron sodium silicate glass surfaces

A series of (SiO2)(0.7-x)(Na2O)(0.3)(Fe2O3)(x) glasses (0.0 less than or equal to x less than or equal to 0.18) were prepared and investigated by means of X-ray photoelectron spectroscopy (XPS). The quantitative ratio [Fe2+]/[Fe-total], for each glass has been determined from an analysis of the Fe 3p spectra. For low Fe2O3 content both iron valencies are present, however, it was found that Fe3+ is the dominant species for high Fe2O3. From an analysis of the O 1s spectra, it was possible to discriminate between bridging and non-bridging oxygen atoms. It was found that the ratio of the non-bridging oxygen content to the total oxygen content increases with increasing iron concentration. It has also been shown that the non-bridging oxygen contribution to the O 1s spectra can be simulated by summing the contributions from the SiONa, SiOFe(II) and SiOFe(III) components present in the glass.