Charging and mixing effects during the XPS analysis of mixtures of oxides

In this article we present an XPS analysis of mixtures of Al 2 O 3 and TiO 2 powders of different relative size in order to study differential charging effects. To illustrate some of the possible situations we have studied the behaviour of three different samples: (1) very large (microns) and porous particles of Al 2 O 3 supporting TiO 2 particles of relatively small size (300 Å); (2) Al 2 O 3 and TiO 2 particles of similar size (300 Å); and (3) very small particles (20–30 Å) of TiO 2 dispersed in Al 2 O 3 particles of 300 Å. The observed effects are then analysed by using Auger parameters and relative binding energies and discussed in terms of the different morphologies of the samples, as determined by TEM. The influence on charging of an electron flood gun and of Ar + sputtering is also presented. In addition, ion‐induced mixing effects have been clearly observed in the case of very small particles of TiO 2 dispersed on alumina.