To facilitate the next generation of high-power white-light-emitting diodes (white LEDs), the discovery of more efficient red-emitting phosphor materials is essential. In this regard, the hardly explored compound class of nitridoaluminates affords a new material with superior luminescence properties. Doped with Eu(2+), Sr[LiAl3N4] emerged as a new high-performance narrow-band red-emitting phosphor material, which can efficiently be excited by GaN-based blue LEDs. Owing to the highly efficient red emission at λ(max) ~ 650 nm with a full-width at half-maximum of ~1,180 cm(-1) (~50 nm) that shows only very low thermal quenching (>95% relative to the quantum efficiency at 200 °C), a prototype phosphor-converted LED (pc-LED), employing Sr[LiAl3N4]:Eu(2+) as the red-emitting component, already shows an increase of 14% in luminous efficacy compared with a commercially available high colour rendering index (CRI) LED, together with an excellent colour rendition (R(a)8 = 91, R9 = 57). Therefore, we predict great potential for industrial applications in high-power white pc-LEDs.

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.

The new nitridoalumosilicate phosphor SrAlSi 4 N 7 :Eu 2+ has been synthesized under nitrogen atmosphere at temperatures up to 1630 °C in a radio-frequency furnace starting from Sr metal, R-Si 3 N 4 , AlN, and additional Eu metal. The crystal structure of the host compound SrAlSi 4 N 7 has been solved and refined on the basis of single-crystal and powder X-ray diffraction data. In the solid, there is a network structure of corner-sharing SiN 4 tetrahedra incorporating infinite chains of all edge-sharing AlN 4 tetrahedra running along [001] (SrAlSi 4 N 7 : Pna2 1 (No. 33), Z ) 8, a ) 11.742(2) Å, b ) 21.391(4) Å, c ) 4.966(1) Å, V ) 12.472(4) Å 3 , 2739 reflections, 236 refined parameters, R1 ) 0.0366). The Eu 2+ -doped compound SrAlSi 4 N 7 :Eu 2+ shows typical broadband emission originating from dipole-allowed 4f 6 ( 7 F J )5d 1 f 4f 7 ( 8 S 7/2 ) transitions in the orange-red spectral region (λ max ) 632 nm for 2% Eu doping level, 450 nm excitation) with a spectral width of FWHM ) 2955 (( 75) cm -1 and a Stokes shift ∆S ) 4823 (( 100) cm -1 . The luminescence properties make the phosphor an attractive candidate material as red component in trichromatic warm white light LEDs with excellent color rendition properties.

Group (III) Nitrides M[Mg 2Al2N4] (M: Ca, Sr, Ba, Eu) and Ba[Mg2Ga2N4]-Structural Relation and Nontypical Luminescence Properties of Eu 2+ Doped Samples. -The new compounds (V), (VIII), and (X) are characterized by powder and single crystal XRD, SEM, UV/VIS spectroscopy, and luminescence spectroscopy. All the compounds crystallize in space group I4/m with Z = 2 (UCr 4C4-type structure), forming highly condensed anionic networks of disordered (Al/Mg)N 4 and (Ga/Mg)N4 units, connected to each other by common edges and corners. M 2+ (M: Ca, Sr, Ba, Eu) is centered in vierer ring channels and cuboid-like coordinated by N. Eu 2+ doped samples of (VIIIa-c) exhibit nontypical luminescence properties including trapped exciton emission in the red spectral region. -(PUST, P.; HINTZE, F.; HECHT, C.; WEILER, V.; LOCHER, A.; ZITNANSKA, D.; HARM, S.; WIECHERT, D.; SCHMIDT, P. J.; SCHNICK*, W.; Chem. Mater. 26 (2014) 21, 6113-6119,