Materials Data on AlCrFeO4 by Materials Project

FeCrAlO4 is Spinel-derived structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Cr3+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six equivalent FeO4 tetrahedra, edges with two equivalent CrO6 octahedra, and edges with four equivalent AlO6 octahedra. There are four shorter (2.03 Å) and two longer (2.04 Å) Cr–O bond lengths. Fe2+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six equivalent CrO6 octahedra and corners with six equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–65°. There are two shorter (2.02 Å) and two longer (2.04 Å) Fe–O bond lengths. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent FeO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent CrO6 octahedra. There is two shorter (1.92 Å) and four longer (1.96 Å) Al–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Cr3+, one Fe2+, and one Al3+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Cr3+, one Fe2+, and two equivalent Al3+ atoms.