Behavior of aluminum nitride ceramic surfaces under hydrothermal oxidation treatments

AlN ceramics were prepared by pressureless sintering of the nitride powders with mixtures containing yttria, magnesia and silicon nitride at 1900°C. To investigate the sensitivity of these ceramics to hydrothermal treatments, samples were treated in oxygen-containing atmospheres for different exposure times and temperatures. During the exposure, a thin layer of oxide develops and coats the ceramic surface. A variety of physical and chemical methods of analysis were used to characterize the resulting materials. Surface roughness, morphology, and weight changes during exposure were followed. The ceramic phases as formed during the sintering step and additional treatments have been characterized using X-ray photoelectron spectroscopy (XPS), and the photoelectron binding energies for the pure and reacted phases are reported. The XPS technique was also used to follow the surface evolution of the solid/gas interface produced by the surface treatments