BaSi₄O₆N₂ – A Hexacelsian‐Type Layered Oxonitridosilicate

Abstract

With BaSi 4 O 6 N 2 it was possible to synthesize a new compound in the hexacelsian structure type that has not been observed for nitrido-or oxonitridosilicates before. BaSi 4 O 6 N 2 was obtained by employing the multi-anvil technique at pressures of 12-15 GPa and temperatures between 900 and 1200°C starting from BaSi 2 O 2 N 2 . The crystal structure of Ba-Si 4 O 6 N 2 was solved on the basis of X-ray powder diffraction data [P6/mmm, no. 191, a = 5.3512(2) Å, c = 7.5235(4) Å, V = 186.57 Å 3 , Z = 1, R wp = 0.065] and was refined by the Rietveld method employing difference Fourier analyses. BaSi 4 O 6 N 2 represents a nonbranched double-layer silicate with a high degree of condensation [κ = 0.5, i.e. the atomic ratio n(Si)/ n (O,N)]. The layers of BaSi 4 O 6 N 2 are made up of vertex-shar-Nitrido-and oxonitridosilicates [1] [e.g. γ-Si 3 N 4 , [2,3] SiAlONs, [1,4] M 2 Si 5 N 8 :Eu 2+ (M = Ca, Sr, Ba), [5][6][7] Eu 2 Si 5 N 8 , [8] MSi 2 O 2 N 2 :Eu 2+ (M = alkaline earth) [9][10][11][12] ] are well known to exhibit interesting physical [1,13,14] and luminescence properties. [1,[15][16][17][18][19] High-pressure/high-temperature investigations (HP/HT) on nitrido-and oxonitridosilicates turned out to be promising for the finding of new HP/HT modifications as well as for the understanding of their phase behavior under extreme conditions. [1,20] Recently, the new green phosphor Ba 3 Si 6 O 12 N 2 :Eu 2+ was discovered and studied thoroughly. [21][22][23] The luminescence properties were promising [21][22][23] due to an outstandingly small Stokes shift and a narrow emission band. The structure of BaSi 4 O 6 N 2 resembles that of Ba 3 Si 6 O 12 N 2 :Eu 2+ and, since technical applicability is an important requirement for potential LED phosphors, the stability of BaSi 4 O 6 N 2 has been thoroughly investigated under various conditions (HP/ HT). In the literature nonbranched silicate double layers, which are the characteristic building unit of the new phase, are well known for the feldspar high-temperature phases MAl 2 Si 2 O 8 (M = Ca, Sr, Ba) [24][25][26][27][28] but are unknown for [a]

Computational Chemistry Approach for White LED (Oxy)Nitride Phosphors

“…Even if this challenging problem (beyond LDA/GGA for rareearth ions) could be theoretically resolved, such level of computation of large supercell models doped with rare-earth ions would be computationally demanding. Once such elaborate computation could be realized, we could make plausible luminescent center models to explain puzzling luminescent properties of many (oxy)nitride phosphors, such as BaSi 4 O 6 N 2 :Eu (no luminescence) 62 vs. BaSi 2 O 2 N 2 :Eu (bluish-green luminescence). The combination of this theoretical approach with photo-conductivity measurement may also be interesting, since the 5d level determined by photo-conductivity analysis (such as Y 3 (Al,Ga) 5 O 12 :Ce 63 ) may be endorsed by theoretical evaluation, or vise versa.…”

Eu- and Tb-adsorbed Si3N4and Ge3N4: tuning the colours with one luminescent host

“…In particular, Eu 2+ -doped (oxo)nitridosilicates and SiAlONs have been amply studied as important host lattices for phosphor-converted light-emitting diodes (pc-LEDs). 8–25…”

“…In particular, Eu 2+ -doped (oxo)nitridosilicates and SiAlONs have been amply studied as important host lattices for phosphor-converted light-emitting diodes (pc-LEDs). [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25] For instance, M 2 Si 5 N 8 :Eu 2+ (red-orange, 2-5-8 phosphor) and MSi 2 O 2 N 2 :Eu 2+ (yellow-green, 1-2-2-2 phosphor) (M = Ca, Sr, Ba) were signicant discoveries in this eld. Several Mgnitridosilicates and nitridoaluminates were also developed as next generation high efficient red emitting phosphor materials with superior luminescence properties.…”

Eu- and Tb-adsorbed Si3N4 and Ge3N4: Tuning the colours with one luminescent host

“…In particular, Eu 2+ -doped (oxo)nitridosilicates and SiAlONs have been amply studied as important host lattices for phosphor-converted light-emitting diodes (pc-LEDs). [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22] For instance, M2Si5N8:Eu 2+ (red-orange, 2-5-8 phosphor) and MSi2O2N2:Eu 2+ (yellow-green,1-2-2-2 phosphor) (M = Ca, Sr, Ba) were significant discoveries in this field. Several Mgnitridosilicates and nitridoaluminates were also developed as next generation high efficient red emitting phosphor materials with superior luminescence properties.…”