Tantalum nitrides (TaNx) nanocrystals with different phase and morphology have been synthesized through homogenous sodium reduction under low temperature with the subsequent annealing process under high vacuum. The crystal structures of tantalum nitrides were determined by Rietveld refinement based on the X-ray diffraction data. The morphologies of various tantalum nitrides nanocrystals in high quality were analyzed through the electron microcopies examinations. The spherical TaN nanoparticles, cuboidal TaN0.83 and TaN0.5 nanocrystals have been selectively prepared at different annealing temperatures. In addition, the specific surface areas of the tantalum nitrides nanocrystals measured by BET method were around 9.87-11.64 m(2) g(-1), indicating that such nano-sized tantalum nitrides could be suitable for capacitor with high specific capacitance. Crown Copyright (C) 2012 Published by Elsevier Ltd. All rights reserved.