Crystal structures and luminescence properties of Li6 MN4:Ce3+ (M = Mo, W)

Abstract The compounds Li 6 MoN 4 and Li 6 WN 4 were prepared from the reactants M ( M = Mo, W) and Li 3 N in a radiofrequency furnace at 1000 °C. The lithonitridometallates crystallize in the tetragonal system with the lattice parameters: a = 6.6844(1), c = 4.9294(1) Å for Li 6 WN 4 based on single-crystal X-ray diffraction data and a = 6.6611(3), c = 4.9338(3) Å for Li 6 MoN 4 taken from powder X-ray diffraction data. Colorless to slightly reddish single-crystals of the tungsten compound were isolated and the crystal structure was refined in the space group P 4 2 / nmc (no. 137) with Z = 2 and the powder X-ray data of the molybdenum compound were analyzed by a Rietveld refinement. Both structures belong to the Li 6 [ZnO 4 ] type published by Hoppe et al. in 1987 (Untenecker H., Hoppe R. Z. Anorg. Allg. Chem. 1987, 551 , 147–150) and could be doped with Ce 3+ for the first time. The investigated compounds show a reddish color impression upon UV to blue irradiation and exhibit a broad emission band with a maximum at λ max = 693 nm (fwhm 97 nm) for Li 6 MoN 4 and at λ max = 653 nm (fwhm 133 nm) for Li 6 WN 4 .