Toward New Phosphors for Application in Illumination-Grade White pc-LEDs: The Nitridomagnesosilicates CaLMg3SiN4]:Ce~(3+), Sr[Mg3SiN4]:Eu~(2+), and Eu[Mg3SiN4]

摘要

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 I4_1/a (No. 88). Crystal structures were solved and refined from single-crystal X-ray diffraction data (Z = 16, Ca[Mg3SiN4]:Ce~(3+), a = 11.424(2), c = 13.445(3) A, Rl = 0.040, wR2 = 0.106; Sr[Mg3SiN4]:Eu~(2+), a = 11.495(2), c = 13.512(3) A, Rl = 0.036, wR2 = 0.102; Eu[Mg3SiN4], a = 11.511(4), c = 13.552(4) A, Rl = 0.016, wR2 = 0.039). The nitridomagne-sosilicates are isotypic to Na[Li3SiO4], containing a condensed tetrahedra network with a high degree of condensation (i.e., atomic ratio (Mg,Si):N) k = 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[Mg3SiN4] show yellow emission (λ_(max) = 530 and 585 nm, fwhm ~3900 cm~(-1) (~130 nm)), while Sr[Mg3SiN4]:Eu~(2+) exhibits red luminescence (λ_(max) = 615 ran) 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`65d~1 → 4f~7 transition in Eu~(2+), Sr[Mg3SiN4] :Eu~(2+) may point the way to the next generation red phosphor materials for application in illumination-grade white pc-LEDs.