DOE OSTI2020
FeTaO4 is zeta iron carbide-derived structured and crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are two inequivalent Ta5+ sites. In the first Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of Ta–O bond distances ranging from 1.92–2.13 Å. In the second Ta5+ site, Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of Ta–O bond distances ranging from 1.92–2.14 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 48–54°. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four TaO6 octahedra, corners with four FeO6 octahedra, and edges with two equivalent TaO6 octahedra. The corner-sharing octahedra tilt angles range from 48–55°. There are a spread of Fe–O bond distances ranging from 1.96–2.15 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe3+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ta5+ and two Fe3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Ta5+ and one Fe3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ta5+ and two Fe3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ta5+ and two equivalent Fe3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ta5+ and one Fe3+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ta5+ and two equivalent Fe3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ta5+ and one Fe3+ atom.