Real structure of (Sb1/3Zn2/3)GaO3(ZnO)3, a member of the homologous series ARO3(ZnO)m with ordered site occupation

Abstract The hitherto unknown compound (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) 3 , a member of the homologous series with general formula AR O 3 (ZnO) m ( A , R = trivalent metal cation), was prepared by solid state methods from the binary oxides in sealed Pt-tubes. The structure of (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) 3 has been determined by X-ray diffraction from flux-grown single crystals ( R 3 m , Z = 3, a R = 3.2387(7) A, c R = 41.78(1) A. The analysis revealed that (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) m is isostructural with InGaO 3 (ZnO) m , where In 3+ on octahedral sites is replaced by Sb 5+ and Zn 2+ in a ratio of 1:2, preserving an average charge of 3+. (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) 3 was furthermore analyzed by electron diffraction, High Angle Annular Dark Field (HAADF) scanning TEM, and high precision EELS spectroscopic imaging, where a periodic ordering of SbO 6 octahedra connected via edge sharing to six ZnO 6 octahedra in the octahedral layers in a honeycomb motif is found. Due to the large lateral distance of ca. 1.4 nm between adjacent octahedral layers, electrostatic interaction might hardly dictate Sb and Zn positions in neighbouring layers, and hence is a characteristic of the real structure of (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) 3 . A structure model of the compound in space group P 3 1 12 (Nr. 151) with strictly ordered and discrete Sb and Zn positions is derived by crystallographic transformations as closest approximant for the real structure of (Sb 1/3 Zn 2/3 )GaO 3 (ZnO) 3 . UV–vis measurements confirm this compound to be a transparent oxide with an optical band gap in the UV region with E g = 3.15 eV.