SYNTHESIS AND CHARACTERIZATION OF NEW BIMETALLIC TRANSITION-METAL OXYNITRIDES - M(I)-M(II)-O-N (M(I), M(II)=V, MO, W AND NB)

A new class of materials, M(I)-M(II)-O-N (where M(I), M(II) = V, Mo, W , and Nb), has been synthesized by nitriding bimetallic oxide precurso rs with ammonia gas via a temperature programmed reaction. The oxide p recursors are prepared by conventional solid state reaction between tw o appropriate monometallic oxides. The synthesis of the oxynitrides in volves passing NH3 gas over the oxide precursors at a flow rate of 6.8 0 x 10(2) mu mol s(-1) (1000 cm(3) min(-1)), and raising the temperatu re at a rate of 8.3 x 10(-2) K s(-1) (5 K min(-1)) to a final temperat ure which is held constant for a short period of time. The oxynitrides thus obtained are pyrophoric and need to be passivated before exposin g them to air. All these new bimetallic oxynitrides have a face center ed cubic (f.c.c.) metal arrangement and high values of surface area. T heir surface activity is assessed from their ability to chemisorb CO.