Monometallic oxynitrides containing transition metals of the groups 5 and 6 starting from freeze-dried precursors

Early transition elements oxynitrides M(OxNy) ( M = V, Mo, Cr and W) have been obtained by direct ammonolysis of precursors resulting from the freeze-drying of aqueous solutions of the appropriate metal salts. A study of the influence of the preparative variables on the outcomes of this procedure is presented. Monometallic oxynitrides have been prepared as single phases by direct ammonolysis of the respective freeze-dried precursors at the appropriate conditions (temperature, time and cooling rate). All the compounds have the rock-salt crystal structure, in which the metal atoms are in a face-centred cubic arrangement, with non-metal atoms occupying octahedral interstitial positions. The materials have been characterized by X-ray powder diffraction, elemental analysis and thermogravimetric analysis under oxygen flow