Polymorphism and polymorph-dependent luminescence properties of the first lithium oxonitridolithosilicate Li₃SiNO₂:Eu²⁺

Abstract

Building on studies of monoclinic Li3SiNO2, a polymorph, β-Li3SiNO2, with a previously unknown structure type was synthesized. The β-phase crystallizes in the orthorhombic space group Pbca (no. 61) with lattice...

An Unexpected New Member of the Family of Lithium Oxonitridosilicates – Li7Si2NO6

“…The fact that this is none of the predicted compounds, that it is only the second lithium oxonitridolithosilicate after Li 3 SiNO 2 and that it also crystallizes in a new structure type containing the unprecedented building units of a [LiN 2 O 2 ]-tetrahedron and a [Si 2 NO 6 ]-disilicate unit, makes it even more interesting. [9,14] Moreover, these results illustrate that this substance class is still not fully described, after 70 years from the first publication by Juza et al, and continues to be a rewarding field of studies. [1] Experimental Section Synthesis Using a high-temperature solid-state reaction in open nickel crucibles under nitrogen flow it was possible to obtain single crystals from the starting materials SiO 2 (3.11 mmol, Fluka, > 99.9 %), Li 3 N (3.11 mmol, Aldrich, > 99.5 %), and Li 2 O (3.11 mmol, Aldrich, 97 %) at temperatures of 900 °C.…”

“…For example, the SiN 3 O tetrahedra in LiSiNO lead to the formation of layers, the SiN 2 O 2 tetrahedra in Li 3 SiNO 2 form single chains, and the SiNO 3 tetrahedra of Li 7 Si 2 NO 6 form dimers. [3,9,14] Consequently, as far as nitrogen is present, it seems unlikely that a nesosilicate will form while the lithium content increases. This raises the question to which lithium content these compounds tolerate the dilution of the silicate units and remain stable.…”

“…[20][21][22][23] Since lithium occurs not only as part of the tetrahedra network, but also as completing cation in octahedral coordination, the most precise classification is as a lithium oxonitridolithosilicate with the sum formula Li 2 [Li 5 Si 2 NO 6 ]. [9,14] A full structural overview can be found in Figure 1.…”