We have investigated the thermal stability of GaN powders using DTA-TG, XRD, and XPS. GaN powders have been treated below 1400 degrees C in the flowing stream of N-2 gas. The pure GaN powders is indecomposable below 1120 degrees C, but annealing at 1050 degrees C results in the degradation of the crystalline quality of the GaN powders. With the increase of the temperature, more and more GaN powders are separated into Ga metal in the temperature range of 1120-1312 degrees C, but the decomposition of GaN is propitious to improvement of the crystalline quality of GaN. When the temperature exceeds 1312 degrees C, all the GaN powders are converted into Ga metal. The morphology of the samples obtained in the different temperature regimes was investigated using SEM. The results indicate that the average size of the samples obtained at the decomposition temperature regimes of the GaN powders is bigger. (C) 2007 Elsevier B.V. All rights reserved.