title: The unusual surface chemistry of α-Al(2)O(3) (0001).
abstract: We report on the influence of heat treatment on the surface chemistry of an α-alumina crystal. We compare its electrical double layer behaviour with that of 150 nm diameter α-Al(2)O(3) particles. Surface spectroscopy and zeta potential studies are used to understand the changes in surface chemistry. The pH(pzc) of an α-Al(2)O(3) (0001) single crystal (∼4) is more acidic than that of α-Al(2)O(3) particles (8.5), a difference explained by the dominance of [triple bond, length as m-dash]Al(2)OH surface groups on the single crystals and their charging behaviour. Heat treatment of the alumina surface causes a substantial decrease in the number of surface OH groups. Heating at 500 °C decreases the surface density of hydroxyl groups. Heating at 1050 °C also affects surface morphology and surface chemistry. The increased magnitude of the zeta potential and the pH(pzc) shift to lower pH suggest a surface reconstruction and the appearance of more acidic aluminium sites.
authors.affiliation: Ian Wark Research Institute, University of South Australia, Mawson Lakes SA 5095, Australia.
authors.forename: Die
authors.initials: D
authors.lastname: Yang
authors.forename: Marta
authors.initials: M
authors.lastname: Krasowska
authors.forename: Rossen
authors.initials: R
authors.lastname: Sedev
authors.forename: John
authors.initials: J
authors.lastname: Ralston