[en] Nanocrystalline rare earth nitrides (EuN and YbN) were successfully prepared by the thermal decomposition of amides (Eu(NH₂)₂, Yb(NH₂)₂ and Yb(NH₂)₃). The formation processes of nanocrystalline nitrides were characterized by X-ray diffraction analysis (XRD) combined with temperature-programmed desorption (TPD) techniques. The amides were first decomposed to form imide with evolution of NH₃ and subsequently the conversion into nitride occurred. The surface areas increased markedly with increase in temperatures and went up to 146 m² g^-1 upon thermal decomposition of Yb(NH₂)₂ to YbN around 773 K, while EuN obtained by the thermal decomposition of Eu(NH₂)₂ at 573 K yielded surface areas of 107 m² g^-1. Such nanocrystalline YbN and EuN readily reacted with ammonia even at room temperature upon contact with ammonia (0-4.67 kPa). The properties of ammonia taken up by the nitride were evaluated by TPD and XRD. XRD of the NH₃-treated YbN showed diffraction peaks shifted to lower angles, indicating that the ammonia molecules entered the crystal lattice with the expansion of crystal constants