Polymorphism and polymorph-dependent luminescence properties of the first lithium oxonitridolithosilicate LiSiNO:Eu

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 52; no. 15; pp. 49 - 491
• Main Authors: Rießbeck, Kilian M, Wimmer, Daniel S, Seibald, Markus, Baumann, Dominik, Wurst, Klaus, Heymann, Gunter, Huppertz, Hubert
• Format: Journal Article
• Published: 11.04.2023
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/d2dt03921d

Building on studies of monoclinic Li 3 SiNO 2 , a polymorph, β-Li 3 SiNO 2 , with a previously unknown structure type was synthesized. The β-phase crystallizes in the orthorhombic space group Pbca (no. 61) with lattice parameters of a = 18.736(2), b = 11.1267(5), c = 5.0897(3) Å, and a cell volume of V = 1057.2(1) Å 3 . Using high-temperature solid-state reactions in sealed tantalum tubes, it was possible to obtain high purity samples (<5 wt% of side phase LiSi 2 N 3 according to Rietveld analysis) containing exclusively one or the other polymorph, depending solely on the cooling rate. In contrast to the monoclinic phase, orthorhombic β-Li 3 SiNO 2 additionally contains a third layer and shows a layer-sequence of the type ABCB . Doped with the activator ion Eu 2+ , the new polymorph exhibits an intense yellow emission ( λ max = 586 nm, fwhm = 89 nm, 0.33 eV, 2650 cm −1 ) under irradiation with UV to blue light. Hence, the structural difference between the two polymorphs goes along with a significant blue-shift of 16 nm. The results from single-crystal diffraction and single-grain luminescence measurements were confirmed by Rietveld analysis of bulk samples and powder luminescence data. A polymorph of the compound Li 3 SiNO 2 has been synthesized via high temperature solid-state synthesis. The formation of the polymorphs, which show different luminescence properties when doped with Eu( ii ), can be controlled very selectively.