Toward New Phosphors for Application in Illumination-Grade White pc-LEDs: The Nitridomagnesosilicates Ca[Mg₃SiN₄]:Ce³⁺, Sr[Mg₃SiN₄]:Eu²⁺, and Eu[Mg₃SiN₄]

The isotypic compounds M[Mg 3 SiN 4 ] (M = Ca,Sr,Eu) have been synthesized by solid-state reactions in sealed tantalum ampules or in a radio-frequency furnace. The nitridomagnesosilicates crystallize in space group I 4 1 / a (No. 88). Crystal structures were solved and refined from single-crystal X-ray diffraction data ( Z = 16, Ca[Mg 3 SiN 4 ]:Ce 3+, a = 11.424(2), c = 13.445(3) Å, R1 = 0.040, wR2 = 0.106; Sr[Mg 3 SiN 4 ]:Eu 2+, a = 11.495(2), c = 13.512(3) Å, R1 = 0.036, wR2 = 0.102; Eu[Mg 3 SiN 4 ], a = 11.511(4), c = 13.552(4) Å, R1 = 0.016, wR2 = 0.039). The nitridomagnesosilicates are isotypic to Na[Li 3 SiO 4 ], containing a condensed tetrahedra network with a high degree of condensation (i.e., atomic ratio (Mg,Si):N) κ = 1. The crystal structures were confirmed by Rietveld refinement, lattice energy (MAPLE) calculations, and further investigated by 29 Si-MAS NMR. Ce 3+ -doped samples of Ca[Mg 3 SiN 4 ] show yellow emission (λ max = 530 and 585 nm, fwhm ∼3900 cm –1 (∼130 nm)), while Sr[Mg 3 SiN 4 ]:Eu 2+ exhibits red luminescence (λ max = 615 nm) with the most narrow red emission of Eu 2+ -phosphors reported in the literature so far (fwhm ∼1170 cm –1 (∼43 nm)). According to this outstanding narrow red emission, originating from parity allowed 4f 6 5d 1 → 4f 7 transition in Eu 2+, Sr[Mg 3 SiN 4 ]:Eu 2+ may point the way to the next generation red phosphor materials for application in illumination-grade white pc-LEDs.