Two kinds of GaN powders were grown using the chemical vapor transport process, which involved different Ga sources, i.e., Ga2O3 and Ga metal. Although both GaN powders have a wurtzite crystal structure, which was confirmed by powder X-ray diffraction, their structural and optical properties were different. The powders prepared using the gallium nitridation method revealed a hexagonal morphology. The particles were approximately 2 mu m in size, and we determined the large face (0002) by selective area electron diffraction, indicating that they had good crystallinity. In addition, the oxygen content was relatively low, similar to the GaN bulk grown by hydride vapor phase epitaxy. A strong band-edge luminescence was observed in the photoluminescent and cathodoluminescent spectra. However, the powders prepared using the Ga2O3 nitridation method had an irregular morphology, and several tens of nanometer in size. The grain boundaries and the amorphous regions can be seen using high-resolution transmission electron microscopy imaging. Moreover, the oxygen concentration was relatively high. In this paper, we describe the different properties of these two kinds of powders using growth kinetics. (C) 2013 Elsevier B.V. All rights reserved.