Tailoring Emission Characteristics: Narrow-Band Red Luminescence from SLA to CaBa[Li₂Al₆N₈]:Eu²⁺

Narrow-band red-emitting luminescent CaBa[Li2Al6N8]:Eu2+ for potential application in illumination-grade white-light-emitting diodes (WLEDs) was synthesized by reaction of the metal hydrides and nitrides in molybdenum crucibles in a hot isostatic press. Upon irradiation with high-energy visible light (444 nm), the material exhibits intense red and infrared luminescence (emission maxima, 636–639 nm, 790 nm; full width at half-maximum (fwhm), 1095–1266 cm–1 (48–57 nm), ≈1450 cm–1 (89 nm)). The red emission from Eu occupying the Ba site is nearly optimal for use in WLEDs combining outstanding color rendition and excellent luminous efficacy and the most narrow-band Eu2+ emission observed to date. The infrared emission intensity from Eu occupying the Ca site can be limited by reducing the activator concentration (here, 0.02–5 atom % Eu). CaBa[Li2Al6N8]:Eu2+ crystallizes isotypically with RbNaLi6Si2O8 in the monoclinic space group C2/m (no. 12) with unit cell parameters a = 16.0851(2), b = 6.467 38(4), c = 8.042 42(13) Å, β = 90.004(2)°, and Z = 4. The material is obtained almost phase pure with <4 wt % AlN as side phase. The crystal structure consists of a network of vertex- and edge-sharing AlN4 and LiN4 tetrahedra with differently sized four-membered ring channels along [010] occupied by either cubelike coordinated Ca or Ba atoms or left empty.