Gollé-Leidreiter, PhilippPhilippGollé-LeidreiterBhat, ShrikantShrikantBhatWiehl, LeonoreLeonoreWiehlWen, QingboQingboWenKroll, P.P.KrollIshikawa, RyoRyoIshikawaEtter, MartinMartinEtterFarla, Robert J.M.Robert J.M.FarlaIkuhara, Yuichi H.Yuichi H.IkuharaRiedel, Ralf R.Ralf R.RiedelKolb, UteUteKolb2024-08-272024-08-272024https://publica.fraunhofer.de/handle/publica/47417110.1107/S20525206240026832-s2.0-8519564411338728046SnGe4N4O4 was synthesized at high pressure (16 and 20 GPa) and high temperature (1200 and 1500°C) in a large-volume press. Powder X-ray diffraction experiments using synchrotron radiation indicate that the derived samples are mixtures of known and unknown phases. However, the powder X-ray diffraction patterns are not sufficient for structural characterization. Transmission electron microscopy studies reveal crystals of several hundreds of nanometres in size with different chemical composition. Among them, crystals of a previously unknown phase with stoichiometry SnGe4N4O4 were detected and investigated using automated diffraction tomography (ADT), a three-dimensional electron diffraction method. Via ADT, the crystal structure could be determined from single nanocrystals in space group P63 mc, exhibiting a nolanite-type structure. This was confirmed by density functional theory calculations and atomic resolution scanning transmission electron microscopy images. In one of the syntheses runs a rhombohedral 6R polytype of SnGe4N4O4 could be found together with the nolanite-type SnGe4N4O4. The structure of this polymorph was solved as well using ADT.enopen access3D electron diffractionhigh pressure-high temperature (HP-HT) synthesisoxynitridesjournal article