Abstract Amorphous silicon nitride powders have been prepared in a tube reactor in the system silane-argon-ammonia in the temperature range 500–1100 °C. The powders prepared at 500 °C show the presence of elementary silicon. The powders prepared above 650 °C are near stoichiometric in composition, isometric in morphology and the particle size distribution is in the range of 0.05–0.2 μm. The powders prepared at 1100 °C are nearly monodispersive, having the particle size 0.1 μm. The influence of molar ratio of ammonia to silane shows that silicon nitride powder of near stoichiometric composition can be prepared above 11.62 and below this ratio the powders contain elementary silicon. The change in total gas flow rate shows that below 300 cm 3 min −1 the powders again contain elementary silicon and with further increase in flow rate the powders are near stoichiometric at 400 cm −3 min −1 and little hyperstoichiometric in nitrogen content at and above the flow rate of 500 cm −3 min −1. Surface characterization by X-ray photo-electron spectroscopy indicates that most of the oxygen is confined on the surface and is present in the form of SiO 2.