Crystal Structures and Luminescence Properties of RE6Si11N20O:Ce3+ (RE = Lu, Y)

Abstract

The two compounds Lu6Si11N20O and Y6Si11N20O were prepared from the reactants REF3 and “Si(NH)2” in a radiofrequency furnace at 1600 °C. The two oxonitridosilicates crystallise in the trigonal system with the following lattice parameters: Lu6Si11N20O: a = 972.02(3) pm, c = 1050.53(4) pm; Y6Si11N20O: a = 981.09(2) pm, c = 1060.37(3) pm. Colourless to slightly yellowish single crystals of the two compounds were isolated and the measurements of these crystals were solved and refined in space group P31c (no. 159) with Z = 2 and powder X-ray data were analysed by Rietveld refinement. Both structures belong to the Er6[Si11N20]O structure type published by Woike and Jeitschko in 1997 and are doped with Ce3+ for the first time. The investigated compounds show a greenish colour impression by UV to blue radiation and exhibit a broad emission band with an emission maximum at λ max = 552 nm (fwhm 142 nm) for the lutetium compound and λ max = 570 nm (fwhm 159 nm) for the yttrium variant. Compared to YAG:Ce3+, both phosphors show a shift to higher wavelengths making them highly interesting for application in warm-white single phosphor converted light emitting diodes (1 pc-LED) with an improved colour rendering index.