Unexpected Luminescence Properties of Sr0.25Ba0.75Si2O2N2:Eu2+ - A Narrow Blue Emitting Oxonitridosilicate with Cation Ordering

作者：Seibald Markus; Rosenthal Tobias; Oeckler Oliver; Fahrnbauer Felix; Tuecks Andreas; Schmidt Peter J; Schnick Wolfgang^*

来源：Chemistry - A European Journal, 2012, 18(42): 13446-13452.

DOI：10.1002/chem.201201953

• crystal structure determination
• electron diffraction
• HRTEM
• luminescence
• oxonitridosilicates

Owing to a parity allowed 4f6(7F)5d1?4f7(8S7/2) transition, powders of the nominal composition Sr0.25Ba0.75Si2O2N2:Eu2+ (2 mol?% Eu2+) show surprising intense blue emission (?em=472 nm) when excited by UV to blue radiation. Similarly to other phases in the system Sr1-xBaxSi2O2N2:Eu2+, the described compound is a promising phosphor material for pc-LED applications as well. The FWHM of the emission band is 37 nm, representing the smallest value found for blue emitting (oxo)nitridosilicates so far. A combination of electron and X-ray diffraction methods was used to determine the crystal structure of Sr0.25Ba0.75Si2O2N2:Eu2+. HRTEM images reveal the intergrowth of nanodomains with SrSi2O2N2 and BaSi2O2N2-type structures, which leads to pronounced diffuse scattering. Taking into account the intergrowth, the structure of the BaSi2O2N2-type domains was refined on single-crystal diffraction data. In contrast to coplanar metal atom layers which are located between layers of condensed SiON3-tetrahedra in pure BaSi2O2N2, in Sr0.25Ba0.75Si2O2N2:Eu2+ corrugated metal atom layers occur. HRTEM image simulations indicate cation ordering in the final structure model, which, in combination with the corrugated metal atom layers, explains the unexpected and excellent luminescence properties.

• 出版日期2012-10