Ca 18.75 Li 10.5 [Al 39 N 55 ]:Eu 2+ —Supertetrahedron Phosphor for Solid-State Lighting

Highly efficient red-emitting luminescent materials deliver the foundation for next-generation illumination-grade white light-emitting diodes (LEDs). Recent studies demonstrate that the hardly explored class of nitridoaluminates comprises intriguing phosphor materials, e.g., Sr[LiAl 3 N 4 ]:Eu 2+ or Ca[LiAl 3 N 4 ]:Eu 2+ . Here, we describe the novel material Ca 18.75 Li 10.5 [Al 39 N 55 ]:Eu 2+ with highly efficient narrow-band red emission (λ em ≈ 647 nm, full width at half-maximum, fwhm ≈ 1280 cm –1 ). This compound features a rather uncommon crystal structure, comprising sphalerite-like T 5 supertetrahedra that are composed of tetrahedral AlN 4 units that are interconnected by additional AlN 4 moieties. The network charge is compensated by Ca 2+ and Li + ions located between the supertetrahedra. The crystal structure was solved and refined from single-crystal and powder X-ray diffraction data in the cubic space group Fd 3̅ m (No. 227) with a = 22.415(3) Å and Z = 8. To verify the presence of Li, transmission electron microscopy (TEM) investigations including electron energy-loss spectroscopy (EELS) were performed. Based on the intriguing luminescence properties, we proclaim high potential for application in high-power phosphor-converted white LEDs.