Preparation and properties of nanocrystalline ytterbium and europium nitride (YbN and EuN)

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.