Efficient Yellow-Orange Phosphor Lu₄Ba₂[Si₉ON₁₆]O:Eu²⁺ and Orange-Red Emitting Y₄Ba₂[Si₉ON₁₆]O:Eu²⁺: Two Oxonitridosilicate Oxides with Outstanding Structural Variety

The oxonitridosilicate oxides Y 4 Ba 2 [Si 9 ON 16 ]O:Eu 2+ and Lu 4 Ba 2 [Si 9 ON 16 ]O:Eu 2+ have been synthesized starting from RE F 3, RE 2 O 3 ( RE = Y, Lu), BaH 2, Si(NH) 2, and EuF 3 in a radiofrequency furnace at 1550 °C. The crystal structures were solved and refined from single-crystal X-ray data supported with Rietveld refinement on X-ray powder diffraction data. Both compounds are isotypic and crystallize in monoclinic space group P 2 1 / c (no. 14) with Z = 4 and a = 6.0756(2), b = 27.0606(9), c = 9.9471(3) Å, and β = 91.0008(8)° for RE = Y and a = 6.0290(3), b = 26.7385(12), c = 9.8503(5) Å, and β = 90.7270(30)° for RE = Lu. The unique crystal structure exhibits a three-dimensional network made up from Q 4 -type SiN 4 and Q 3 -type SiON 3 tetrahedra. Containing 4-fold bridging N [4] atoms in star-shaped units [N [4] (SiN 3 ) 4 ] next to N [3], N [2], O [1], and noncondensed oxide ions, the title compounds illustrate the vast structural variety in (oxo)nitridosilicates. Under excitation with UV to blue light, Y 4 Ba 2 [Si 9 ON 16 ]O:Eu 2+ shows emission in the orange-red spectral range (λ max = 622 nm, full width at half-maximum (fwhm) ≈ 2875 cm –1 ). Yellow-orange emitting Lu 4 Ba 2 [Si 9 ON 16 ]O:Eu 2+ (λ max = 586 nm, fwhm ≈ 2530 cm –1 ) exhibits high internal quantum efficiency (IQE) ≈ 85%. This makes Lu 4 Ba 2 [Si 9 ON 16 ]O:Eu 2+ a promising phosphor for low color rendering index (CRI) warm white phosphor converted light emitting diodes (pcLEDs).