Oxidation behavior of alpha-SiAlON ceramics doped with Yb, Y, Nd, Ca and Li to the same general molecular formulation was studied at 1000degrees-1300degreesC in dry oxygen. Oxidation resistance of alpha-SiAlON ceramics increased in order of Li, Ca, Nd, Y, and Yb dopants. Oxide layers grown on Nd-, Y-, and Yb-doped samples were dense and crack-free whereas those formed on Ca- and Li-doped samples were porous. The dopant-dependent oxidation behavior of alpha-SiAlON ceramics can be attributed to the effect of the dopants on refractoriness of grain boundary phases and oxide layers as well as to the associated changes in the rate of grain boundary diffusion of dopants and oxygen diffusion in the oxide layers. (C) 2004 Kluwer Academic Publishers.