Y₂₃Sr₁₇[Si₃₈O₁₈N₆₇]O₉. An oxonitridosilicate oxide with a unique layered structure

The oxonitridosilicate oxide Y₂₃Sr₁₇[Si₃₈O₁₈N₆₇]O₉ was synthesized in a radiofrequency furnace at 1450 C starting from YF₃, Y₂O₃, SrH₂ and silicon diimide. The driving force of the metathesis reaction is probably the simultaneous formation of SrF₂ and H₂. The crystal structure was solved and refined from single-crystal X-ray diffraction data in space group P6₃/m (no. 176) with a = 16.5764(4), c = 18.6177(5) Aa, and Z = 2 (R₁ = 0.0196, wR₂ = 0.0377). The results are supported by Rietveld refinement on X-ray powder data, X-ray spectroscopy, and IR spectroscopy. The crystal structure contains [Si₃₈O₁₈N₆₇]^85- layers built up of vertex-sharing SiN₄ and SiON₃ tetrahedra. Lattice energy (MAPLE) and charge distribution (CHARDI) calculations indicate anion and cation ordering, with the exception of one mixed occupied Y/Sr site. UV/Vis spectroscopy and DFT calculations yield an optical optical bandgap of 3.8 eV and an electronic bandgap of 3.6 eV, respectively. (copyright 2019 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)