XPS analysis of the surface of leucite-reinforced feldspathic ceramics

Objective: The bond of a silane-coupling agent to a ceramic surface is expected to be influenced by the composition and chemical state of the ceramic surface. The purpose of this study was to determine the variation in the composition and the chemical states of the surfaces of a range of leucite-reinforced feldspathic (LRF) ceramics using X-ray photoelectron spectroscopy (XPS). Methods: Five LRF ceramic discs (IPS Empress,Optec HSP,VMK 68, Mirage, and a modified Mirage) were produced and polished to a 1 μm finish. A further nine discs of the modified Mirage were produced. The discs were stored for 48 h in a vacuum oven at 110°C to remove absorbed water. The surfaces of these discs were analysed by XPS. Survey scans at 30° take-off angle were taken and surface composition (in at%) was calculated from the narrow scans for Si 2p, O 1s, Al 2p, Mg 2s, K 2p, Na 1s, Ca 2p and N 1s. Results: Atomic concentration of elements (after exclusion of C) for the five LRF ceramics were in the range: O, 45.0–51.6%; Si, 26.7–35.6%; Al, 6.3–9.7%; Mg, 4.9–8.8%; K, 0.5–2.2%; N, 0.9–2.9% and less than 1% of Na and Ca. The shapes of the O 1s and Si 2p narrow scan core lines of the five LRF ceramics were virtually identical. Significance: All five LRF ceramics were found to have a silica-rich surface layer due to a reduction in K and Na relative to the bulk composition. Both the composition and chemical states of the surfaces for the five LRF ceramics were very similar.