Orange-Emitting Li4Sr4[Si4O4N6]O:Eu2+-a Layered Lithium Oxonitridosilicate Oxide

Robin Niklaus; Lukas Neudert; Juliane Stahl; Peter J Schmidt; Wolfgang Schnick

doi:10.1021/acs.inorgchem.8b02391

Orange-Emitting Li₄Sr₄[Si₄O₄N₆]O:Eu²⁺-a Layered Lithium Oxonitridosilicate Oxide

Inorg Chem. 2018 Nov 19;57(22):14304-14313. doi: 10.1021/acs.inorgchem.8b02391. Epub 2018 Nov 6.

Authors

Robin Niklaus¹, Lukas Neudert¹, Juliane Stahl¹, Peter J Schmidt², Wolfgang Schnick¹

Affiliations

¹ Department of Chemistry , University of Munich (LMU) , Butenandtstrasse 5-13 , 81377 Munich , Germany.
² Lumileds Germany GmbH, Lumileds Phosphor Center Aachen , Philipsstrasse 8 , 52068 Aachen , Germany.

PMID: 30398336
DOI: 10.1021/acs.inorgchem.8b02391

Abstract

We report on the structure and properties of the lithium oxonitridosilicate oxide Li₄Sr₄[Si₄O₄N₆]O:Eu²⁺ obtained from solid-state metathesis. The crystal structure was solved and refined from single-crystal X-ray data in the space group P4₂/ nmc (No. 137) [ Z = 2, a = 7.4833(6), c = 9.8365(9) Å, and R1(obs) = 0.0477]. The structure of Li₄Sr₄[Si₄O₄N₆]O:Eu²⁺ is built up from a layered 2D network of SiN₃O tetrahedra and exhibits stacking disorder. The results are supported by transmission electron microscopy and energy-dispersive X-ray spectroscopy as well as lattice energy, charge distribution, and density functional theory (DFT) calculations. Optical measurements suggest an indirect band gap of about 3.6 eV, while DFT calculations on a model free of stacking faults yield a theoretical electronic band gap of 4.4 eV. Samples doped with Eu²⁺ exhibit luminescence in the orange spectral range (λ_em ≈ 625 nm; full width at half-maximum ≈ 4164 cm^-1; internal quantum efficiency at room temperature = 24%), extending the broad field of phosphor materials research toward the sparsely investigated materials class of lithium oxonitridosilicate oxides.