BaSr2Y6O12 crystallizes in the hexagonal P-6 space group. Ba(1) is bonded in a 9-coordinate geometry to three equivalent O(3) and six equivalent O(4) atoms. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. In the second Sr site, Sr(2) is bonded to six equivalent O(1) atoms to form distorted SrO6 pentagonal pyramids that share corners with six equivalent Y(1)O6 octahedra, corners with six equivalent Y(2)O6 octahedra, edges with three equivalent Y(1)O6 octahedra, and faces with two equivalent Sr(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 23-78°. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form YO6 octahedra that share corners with four equivalent Y(2)O6 octahedra, corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Y(1)O6 octahedra, edges with two equivalent Y(2)O6 octahedra, and  an edgeedge with one Sr(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 55-57°. In the second Y site, Y(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form YO6 octahedra that share corners with four equivalent Y(1)O6 octahedra, corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Y(1)O6 octahedra, and edges with two equivalent Y(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-57°. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(2), one Y(2), and two equivalent Y(1) atoms to form a mixture of distorted corner and edge-sharing OSr2Y3 square pyramids. In the second O site, O(2) is bonded to two equivalent Sr(1), one Y(1), and two equivalent Y(2) atoms to form a mixture of distorted corner and edge-sharing OSr2Y3 square pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Y(2), and two equivalent Y(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ba(1), one Y(1), and two equivalent Y(2) atoms.
BaSr2Y6O12 crystallizes in the hexagonal P-6 space group. Ba(1) is bonded in a 9-coordinate geometry to three equivalent O(3) and six equivalent O(4) atoms. All Ba(1)-O(3) bond lengths are 2.76 Å. All Ba(1)-O(4) bond lengths are 3.16 Å. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All Sr(1)-O(2) bond lengths are 2.59 Å. In the second Sr site, Sr(2) is bonded to six equivalent O(1) atoms to form distorted SrO6 pentagonal pyramids that share corners with six equivalent Y(1)O6 octahedra, corners with six equivalent Y(2)O6 octahedra, edges with three equivalent Y(1)O6 octahedra, and faces with two equivalent Sr(2)O6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 23-78°. All Sr(2)-O(1) bond lengths are 2.57 Å. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(2), one O(4), two equivalent O(1), and two equivalent O(3) atoms to form YO6 octahedra that share corners with four equivalent Y(2)O6 octahedra, corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Y(1)O6 octahedra, edges with two equivalent Y(2)O6 octahedra, and  an edgeedge with one Sr(2)O6 pentagonal pyramid. The corner-sharing octahedral tilt angles range from 55-57°. The Y(1)-O(2) bond length is 2.31 Å. The Y(1)-O(4) bond length is 2.28 Å. Both Y(1)-O(1) bond lengths are 2.39 Å. Both Y(1)-O(3) bond lengths are 2.25 Å. In the second Y site, Y(2) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(4) atoms to form YO6 octahedra that share corners with four equivalent Y(1)O6 octahedra, corners with two equivalent Sr(2)O6 pentagonal pyramids, edges with two equivalent Y(1)O6 octahedra, and edges with two equivalent Y(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 55-57°. The Y(2)-O(1) bond length is 2.31 Å. The Y(2)-O(3) bond length is 2.28 Å. Both Y(2)-O(2) bond lengths are 2.37 Å. Both Y(2)-O(4) bond lengths are 2.29 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(2), one Y(2), and two equivalent Y(1) atoms to form a mixture of distorted corner and edge-sharing OSr2Y3 square pyramids. In the second O site, O(2) is bonded to two equivalent Sr(1), one Y(1), and two equivalent Y(2) atoms to form a mixture of distorted corner and edge-sharing OSr2Y3 square pyramids. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(1), one Y(2), and two equivalent Y(1) atoms. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to two equivalent Ba(1), one Y(1), and two equivalent Y(2) atoms.