XPS Study of Surface Cation Segregation in Mullite/Zirconia Composites

We have investigated thermally induced cation surface segregation in mullite/zirconia composites with zirconia content ranging from 0% to 100% using x‐ray photoelectron spectroscopy (XPS). As a result of thermal annealing at 1000°C, slight surface Si enrichment with respect to Al was found in the pure mullite sample (0% zirconia). In contrast to the mullite sample, surface segregation in Si, Na, Al and Y was observed in the pure zirconia sample. The segregation behaviour of all the composite samples (10–90 mass% zirconia) is dominated by the zirconia phase. For samples with 10–100 mass% zirconia, segregation leads to the formation of silicates and sodium oxides at the surface.