Y23Sr17[Si38O18N67]O-9 - An Oxonitridosilicate Oxide with a Unique Layered Structure

摘要

The oxonitridosilicate oxide Y23Sr17[Si38O18N67]O-9 was synthesized in a radiofrequency furnace at 1450 degrees C starting from YF3, Y2O3, SrH2 and silicon diimide. The driving force of the metathesis reaction is probably the simultaneous formation of SrF2 and H-2. The crystal structure was solved and refined from single-crystal X-ray diffraction data in space group P6(3)/m (no. 176) with a = 16.5764(4), c = 18.6177(5) angstrom, and Z = 2 (R-1 = 0.0196, wR(2) = 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.