Sr2Ce2Ti5O15 crystallizes in the trigonal R-3m space group. Sr(1) is bonded to three equivalent O(2) and nine equivalent O(1) atoms to form SrO12 cuboctahedra that share corners with three equivalent Ce(1)O12 cuboctahedra, corners with six equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Ce(1)O12 cuboctahedra,  a faceface with one Ti(2)O6 octahedra, faces with three equivalent Ti(3)O6 octahedra, and faces with four equivalent Ti(1)O6 octahedra. Ce(1) is bonded to three equivalent O(1), three equivalent O(3), and six equivalent O(2) atoms to form CeO12 cuboctahedra that share corners with three equivalent Sr(1)O12 cuboctahedra, corners with nine equivalent Ce(1)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra,  a faceface with one Ti(3)O6 octahedra, faces with three equivalent Ti(1)O6 octahedra, and faces with four equivalent Ti(2)O6 octahedra. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TiO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra, corners with three equivalent Ti(3)O6 octahedra, faces with three equivalent Ce(1)O12 cuboctahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-7°. In the second Ti site, Ti(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form TiO6 octahedra that share corners with three equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one Sr(1)O12 cuboctahedra, and faces with four equivalent Ce(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third Ti site, Ti(3) is bonded to six equivalent O(1) atoms to form TiO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra, faces with two equivalent Ce(1)O12 cuboctahedra, and faces with six equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Sr(1), one Ce(1), one Ti(1), and one Ti(3) atom. In the second O site, O(2) is bonded in a distorted linear geometry to one Sr(1), two equivalent Ce(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Ce(1) and two equivalent Ti(2) atoms.
Sr2Ce2Ti5O15 crystallizes in the trigonal R-3m space group. Sr(1) is bonded to three equivalent O(2) and nine equivalent O(1) atoms to form SrO12 cuboctahedra that share corners with three equivalent Ce(1)O12 cuboctahedra, corners with six equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra, faces with three equivalent Ce(1)O12 cuboctahedra,  a faceface with one Ti(2)O6 octahedra, faces with three equivalent Ti(3)O6 octahedra, and faces with four equivalent Ti(1)O6 octahedra. All Sr(1)-O(2) bond lengths are 2.70 Å. There are six shorter (2.76 Å) and three longer (2.81 Å) Sr(1)-O(1) bond lengths. Ce(1) is bonded to three equivalent O(1), three equivalent O(3), and six equivalent O(2) atoms to form CeO12 cuboctahedra that share corners with three equivalent Sr(1)O12 cuboctahedra, corners with nine equivalent Ce(1)O12 cuboctahedra, faces with three equivalent Sr(1)O12 cuboctahedra,  a faceface with one Ti(3)O6 octahedra, faces with three equivalent Ti(1)O6 octahedra, and faces with four equivalent Ti(2)O6 octahedra. All Ce(1)-O(1) bond lengths are 2.77 Å. All Ce(1)-O(3) bond lengths are 2.70 Å. All Ce(1)-O(2) bond lengths are 2.77 Å. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to three equivalent O(1) and three equivalent O(2) atoms to form TiO6 octahedra that share corners with three equivalent Ti(2)O6 octahedra, corners with three equivalent Ti(3)O6 octahedra, faces with three equivalent Ce(1)O12 cuboctahedra, and faces with four equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 1-7°. All Ti(1)-O(1) bond lengths are 2.00 Å. All Ti(1)-O(2) bond lengths are 1.91 Å. In the second Ti site, Ti(2) is bonded to three equivalent O(2) and three equivalent O(3) atoms to form TiO6 octahedra that share corners with three equivalent Ti(1)O6 octahedra, corners with three equivalent Ti(2)O6 octahedra,  a faceface with one Sr(1)O12 cuboctahedra, and faces with four equivalent Ce(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-7°. All Ti(2)-O(2) bond lengths are 1.99 Å. All Ti(2)-O(3) bond lengths are 1.92 Å. In the third Ti site, Ti(3) is bonded to six equivalent O(1) atoms to form TiO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra, faces with two equivalent Ce(1)O12 cuboctahedra, and faces with six equivalent Sr(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles are 1°. All Ti(3)-O(1) bond lengths are 1.96 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to three equivalent Sr(1), one Ce(1), one Ti(1), and one Ti(3) atom. In the second O site, O(2) is bonded in a distorted linear geometry to one Sr(1), two equivalent Ce(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a distorted linear geometry to two equivalent Ce(1) and two equivalent Ti(2) atoms.