Sr[BeSi2 N4 ]:Eu2+ /Ce3+ and Eu[BeSi2 N4 ]: Nontypical Luminescence in Highly Condensed Nitridoberyllosilicates

Philipp Strobel; Volker Weiler; Peter J Schmidt; Wolfgang Schnick

doi:10.1002/chem.201800912

Sr[BeSi₂ N₄ ]:Eu²⁺ /Ce³⁺ and Eu[BeSi₂ N₄ ]: Nontypical Luminescence in Highly Condensed Nitridoberyllosilicates

Chemistry. 2018 May 17;24(28):7243-7249. doi: 10.1002/chem.201800912. Epub 2018 Apr 30.

Authors

Philipp Strobel¹, Volker Weiler², Peter J Schmidt², Wolfgang Schnick¹

Affiliations

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

PMID: 29575174
DOI: 10.1002/chem.201800912

Abstract

M[BeSi₂ N₄ ] (M=Sr,Eu), crystallizing in the hexagonal space group P6‾ 2c, was synthesized from Sr(NH₂ )₂ , Be₃ N₂ , and "Si(NH)₂ " in W crucibles under a N₂ atmosphere in a radio-frequency furnace. The crystal structure was solved from powder X-ray diffraction data by the charge-flipping method (Sr[BeSi₂ N₄ ]: a=4.86082(2), c=9.42264(4) Å, Z=2; Eu[BeSi₂ N₄ ]: a=4.85848(1), c=9.41615(4) Å). M[BeSi₂ N₄ ] contains a highly condensed rigid network of trigonal planar [BeN₃ ] units that are connected to Si₂ N₇ double tetrahedra by common vertices. M[BeSi₂ N₄ ] (M=Sr,Eu) are the first examples of nitridoberyllosilicates and are isotypic to the oxoberyllate Sr[Be₃ O₄ ]. Eu²⁺ -doped Sr[BeSi₂ N₄ ] and Eu[BeSi₂ N₄ ] show orange-trapped exciton emission (λ_em =605 nm, fwhm ≈126 nm), whereas Ce³⁺ -doped samples of Sr[BeSi₂ N₄ ] show nontypical yellowish-orange luminescence. Sr[BeSi₂ N₄ ] has a large band gap of ≈4.4 eV and shows high chemical and thermal stability. Eu²⁺ -doped beryllates with regular 4f⁶ 5d¹ →4f⁷ -emission could be interesting for future application in LEDs upon doping with Eu²⁺ or Ce³⁺ due to large band gaps, rigid networks, and chemical and thermal stability.

Keywords: beryllates; luminescence; nitrides; nitridosilicates; solid-state structures.