Narrow-Band Green Emitting Nitridolithoalumosilicate Ba[Li₂(Al₂Si₂)N₆]:Eu²⁺ with Framework Topology <i>whj</i> for LED/LCD-Backlighting Applications

Abstract

Eu2+- as well as Ce3+-doped Ba[Li2(Al2Si2)N6] and its related Mg-substituted compounds Ba[(Mg2–xLix) (Al4–xSix)N6]:Eu2+ (x = 0–2) with x = 1.6, 1.8 have been synthesized by metathesis reactions in tantalum ampules. Crystal structures were solved and refined from single-crystal X-ray diffraction data. All three compounds crystallize in tetragonal space group P4/ncc (no. 130) (Z = 4, Ba[Li2(Al2Si2)N6]:Eu2+: a = 7.8282(4), c = 9.9557(5) Å, R1 = 0.0144, wR2 = 0.0366). Their crystal structures, exhibiting the novel framework topology whj, consist of a highly condensed anionic tetrahedra network of disordered (Li/Mg)N4 and (Al/Si)N4 units connected to each other by common edges and corners. The degree of condensation (i.e., atomic ratio (Al,Li,Mg,Si):N) is κ = 1. The Ba2+-position is coordinated eight-fold by N3– in form of a truncated square pyramid. Upon doping with Eu2+, narrow-band emission in the green to yellow spectral range is observed (λem = 532–562 nm, fwhm ≈ 1962 cm–1). Ce3+-doped crystals of Ba[Li2(Al2Si2)N6] show blue emission (λem = 468; 507 nm). According to the tunability of the narrow-band green emission, application in LED-backlight liquid crystal displays appears promising.