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[Mg3SiN4] (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 I41/a (No. 88). Crystal structures were solved and refined from single-crystal X-ray diffraction data (Z = 16, Ca­[Mg3SiN4]:Ce3+, a = 11.424(2), c = 13.445(3) Å, R1 = 0.040, wR2 = 0.106; Sr­[Mg3SiN4]:Eu2+, a = 11.495(2), c = 13.512(3) Å, R1 = 0.036, wR2 = 0.102; Eu­[Mg3SiN4], a = 11.511(4), c = 13.552(4) Å, R1 = 0.016, wR2 = 0.039). The nitridomagnesosilicates are isotypic to Na­[Li3SiO4], 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 29Si-MAS NMR. Ce3+-doped samples of Ca­[Mg3SiN4] show yellow emission (λmax = 530 and 585 nm, fwhm ∼3900 cm–1 (∼130 nm)), while Sr­[Mg3SiN4]:Eu2+ exhibits red luminescence (λmax = 615 nm) with the most narrow red emission of Eu2+-phosphors reported in the literature so far (fwhm ∼1170 cm–1 (∼43 nm)). According to this outstanding narrow red emission, originating from parity allowed 4f65d1 → 4f7 transition in Eu2+, Sr­[Mg3SiN4]:Eu2+ may point the way to the next generation red phosphor materials for application in illumination-grade white pc-LEDs.