The oxidation of AlN powder added by the fluorides at temperatures below 700degreesC in air was discovered in this study. The obvious onset of oxidation of AlN with cryolite and YF3 additions is below 700degreesC with the product of alpha-Al2O3 phase, which usually occurs in single AlN powder above 1100degreesC. The changes on the weight and the FTIR spectra of the AlN powder fired at temperatures lower than 700degreesC show that cryolite and YF3 greatly promote the oxidation of AlN powder at these temperatures. Different from the action of cryolite and YF3 powder, CaF2 has no obvious effect on the oxidation of AlN. A possible oxidation process, in part corroborated by FTIR and XRF, was proposed to explain the results in the experiments. The oxidation kinetics of AlN in the presence of cryolite were also discussed at the temperatures ranging from 550 to 700degreesC from the data of the weight gains in this region. The result shows that the oxidation follows a linear law, which implies a reaction rate-controlled process. The considerably low activation energy of 67 kJ mol(-1), which is associated with the quick oxidation and the formation of alpha-Al2O3 at temperatures below 700degreesC, was determined from the slope of the line fit. (C) 2002 Elsevier Science Ltd. All rights reserved.