Sr6Al12Bi2O27 crystallizes in the trigonal R3 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(5), one O(8), and two equivalent O(2) atoms to form corner-sharing AlO4 tetrahedra. In the second Al site, Al(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form corner-sharing AlO4 tetrahedra. In the third Al site, Al(3) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form corner-sharing AlO4 tetrahedra. In the fourth Al site, Al(4) is bonded to one O(3), one O(4), one O(6), and one O(8) atom to form corner-sharing AlO4 tetrahedra. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent O(9) atoms. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(9) atoms. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Sr(2), one Al(3), one Al(4), and one Bi(2) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(3), one Al(4), and one Bi(1) atom. In the third O site, O(5) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Al(1), and one Al(3) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Sr(2), one Al(2), and one Al(4) atom. In the fifth O site, O(7) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Al(2), and one Al(3) atom. In the sixth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Sr(2), one Al(1), and one Al(4) atom. In the seventh O site, O(9) is bonded to one Sr(1), one Sr(2), one Bi(1), and one Bi(2) atom to form distorted OSr2Bi2 tetrahedra that share edges with two equivalent O(9)Sr2Bi2 tetrahedra and  an edgeedge with one O(1)Sr2Al2 trigonal pyramid. In the eighth O site, O(1) is bonded to one Sr(1), one Sr(2), and two equivalent Al(2) atoms to form distorted OSr2Al2 trigonal pyramids that share corners with two equivalent O(1)Sr2Al2 trigonal pyramids and  an edgeedge with one O(9)Sr2Bi2 tetrahedra. In the ninth O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), and two equivalent Al(1) atoms.
Sr6Al12Bi2O27 crystallizes in the trigonal R3 space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(4), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. The Sr(1)-O(1) bond length is 2.48 Å. The Sr(1)-O(2) bond length is 2.69 Å. The Sr(1)-O(4) bond length is 2.71 Å. The Sr(1)-O(5) bond length is 2.89 Å. The Sr(1)-O(6) bond length is 2.68 Å. The Sr(1)-O(7) bond length is 2.61 Å. The Sr(1)-O(8) bond length is 2.69 Å. The Sr(1)-O(9) bond length is 2.66 Å. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(1), one O(2), one O(3), one O(5), one O(6), one O(7), one O(8), and one O(9) atom. The Sr(2)-O(1) bond length is 2.66 Å. The Sr(2)-O(2) bond length is 2.54 Å. The Sr(2)-O(3) bond length is 2.66 Å. The Sr(2)-O(5) bond length is 2.65 Å. The Sr(2)-O(6) bond length is 2.74 Å. The Sr(2)-O(7) bond length is 2.67 Å. The Sr(2)-O(8) bond length is 2.64 Å. The Sr(2)-O(9) bond length is 2.70 Å. There are four inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(5), one O(8), and two equivalent O(2) atoms to form corner-sharing AlO4 tetrahedra. The Al(1)-O(5) bond length is 1.76 Å. The Al(1)-O(8) bond length is 1.75 Å. There is one shorter (1.75 Å) and one longer (1.77 Å) Al(1)-O(2) bond length. In the second Al site, Al(2) is bonded to one O(6), one O(7), and two equivalent O(1) atoms to form corner-sharing AlO4 tetrahedra. The Al(2)-O(6) bond length is 1.76 Å. The Al(2)-O(7) bond length is 1.74 Å. There is one shorter (1.74 Å) and one longer (1.76 Å) Al(2)-O(1) bond length. In the third Al site, Al(3) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form corner-sharing AlO4 tetrahedra. The Al(3)-O(3) bond length is 1.79 Å. The Al(3)-O(4) bond length is 1.76 Å. The Al(3)-O(5) bond length is 1.75 Å. The Al(3)-O(7) bond length is 1.75 Å. In the fourth Al site, Al(4) is bonded to one O(3), one O(4), one O(6), and one O(8) atom to form corner-sharing AlO4 tetrahedra. The Al(4)-O(3) bond length is 1.76 Å. The Al(4)-O(4) bond length is 1.78 Å. The Al(4)-O(6) bond length is 1.75 Å. The Al(4)-O(8) bond length is 1.75 Å. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent O(9) atoms. All Bi(1)-O(4) bond lengths are 2.78 Å. All Bi(1)-O(9) bond lengths are 2.19 Å. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(9) atoms. All Bi(2)-O(3) bond lengths are 2.68 Å. All Bi(2)-O(9) bond lengths are 2.22 Å. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Sr(2), one Al(3), one Al(4), and one Bi(2) atom. In the second O site, O(4) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Al(3), one Al(4), and one Bi(1) atom. In the third O site, O(5) is bonded in a 2-coordinate geometry to one Sr(1), one Sr(2), one Al(1), and one Al(3) atom. In the fourth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Sr(2), one Al(2), and one Al(4) atom. In the fifth O site, O(7) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Al(2), and one Al(3) atom. In the sixth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Sr(1), one Sr(2), one Al(1), and one Al(4) atom. In the seventh O site, O(9) is bonded to one Sr(1), one Sr(2), one Bi(1), and one Bi(2) atom to form distorted OSr2Bi2 tetrahedra that share edges with two equivalent O(9)Sr2Bi2 tetrahedra and  an edgeedge with one O(1)Sr2Al2 trigonal pyramid. In the eighth O site, O(1) is bonded to one Sr(1), one Sr(2), and two equivalent Al(2) atoms to form distorted OSr2Al2 trigonal pyramids that share corners with two equivalent O(1)Sr2Al2 trigonal pyramids and  an edgeedge with one O(9)Sr2Bi2 tetrahedra. In the ninth O site, O(2) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), and two equivalent Al(1) atoms.