YSr2Fe3O8 crystallizes in the tetragonal P4/mmm space group. Sr(1) is bonded in a 8-coordinate geometry to four equivalent O(1) and four equivalent O(3) atoms. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1) and four equivalent O(2) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O6 octahedra and corners with four equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. In the second Fe site, Fe(2) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Sr(1), one Fe(1), and one Fe(2) atom to form distorted OSr4Fe2 octahedra that share corners with five equivalent O(1)Sr4Fe2 octahedra, corners with eight equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(2)Y2Fe2 tetrahedra, edges with four equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(3)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Fe(1) atoms to form distorted OY2Fe2 tetrahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with ten equivalent O(2)Y2Fe2 tetrahedra, and edges with five equivalent O(2)Y2Fe2 tetrahedra. The corner-sharing octahedral tilt angles are 74°. In the third O site, O(3) is bonded to four equivalent Sr(1) and two equivalent Fe(2) atoms to form a mixture of distorted edge, face, and corner-sharing OSr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°.
YSr2Fe3O8 crystallizes in the tetragonal P4/mmm space group. Sr(1) is bonded in a 8-coordinate geometry to four equivalent O(1) and four equivalent O(3) atoms. All Sr(1)-O(1) bond lengths are 2.79 Å. All Sr(1)-O(3) bond lengths are 2.66 Å. Y(1) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. All Y(1)-O(2) bond lengths are 2.41 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1) and four equivalent O(2) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O6 octahedra and corners with four equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. The Fe(1)-O(1) bond length is 1.86 Å. All Fe(1)-O(2) bond lengths are 2.03 Å. In the second Fe site, Fe(2) is bonded to two equivalent O(1) and four equivalent O(3) atoms to form FeO6 octahedra that share corners with four equivalent Fe(2)O6 octahedra and corners with two equivalent Fe(1)O5 trigonal bipyramids. The corner-sharing octahedra are not tilted. Both Fe(2)-O(1) bond lengths are 2.15 Å. All Fe(2)-O(3) bond lengths are 1.95 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Sr(1), one Fe(1), and one Fe(2) atom to form distorted OSr4Fe2 octahedra that share corners with five equivalent O(1)Sr4Fe2 octahedra, corners with eight equivalent O(3)Sr4Fe2 octahedra, corners with four equivalent O(2)Y2Fe2 tetrahedra, edges with four equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(3)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Fe(1) atoms to form distorted OY2Fe2 tetrahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with ten equivalent O(2)Y2Fe2 tetrahedra, and edges with five equivalent O(2)Y2Fe2 tetrahedra. The corner-sharing octahedral tilt angles are 74°. In the third O site, O(3) is bonded to four equivalent Sr(1) and two equivalent Fe(2) atoms to form a mixture of distorted edge, face, and corner-sharing OSr4Fe2 octahedra. The corner-sharing octahedral tilt angles range from 0-53°.