STUDY OF AMMONOLYSIS REACTIONS WITH IN-SITU X-RAY-DIFFRACTION - DETECTION AND CRYSTAL-STRUCTURE OF LI0.84W1.16N2

The new ternary nitride Li0.84W1.16N2 was found by an in situ X-ray di ffraction study of the ammonolysis of a LIF-WO3 mixture. The ammonolys is proceeds via Li6W2O9 to LiWN2, which subsequently decomposes at 900 degrees C to form Li0.84W1.16N2. For a larger scale synthesis of Li0. 84W1.16N2 the ammonolysis of a mixture of Li2CO3 and WO3 was performed at 900 degrees C, Li0.84W1.16N2 crystallizes in the anti-TiP type str ucture with the space group P6(3)/mmc and a = 2.8809(1) Angstrom, c = 10.3456(4) Angstrom, and Z = 2 as determined from simultaneous Rietvel d refinement of X-ray and neutron powder diffraction data. The refinem ent converged with R(F-2)= 7.0% for the X-ray data and 8.3% for the ne utron data with a total reduced chi(2) = 3.54. The structure consists of alternating layers of WN6 trigonal prisms and MN6 octahedra (M = W, Li), with distances W-N = 2.11 Angstrom. (C) 1998 Academic Press.