Tb3SbO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Tb(1)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-48°. In the second Tb site, Tb(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Tb(1)O7 pentagonal bipyramids, and edges with four equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Sb(1) atoms to form distorted OTb2Sb2 trigonal pyramids that share corners with two equivalent O(4)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with two equivalent O(5)Tb3Sb tetrahedra. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(2)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with four equivalent O(4)Tb4 tetrahedra,  an edgeedge with one O(4)Tb4 tetrahedra, edges with two equivalent O(5)Tb3Sb tetrahedra, and  an edgeedge with one O(1)Tb2Sb2 trigonal pyramid. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(4)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with four equivalent O(2)Tb4 tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with two equivalent O(5)Tb3Sb tetrahedra. In the fifth O site, O(5) is bonded to one Tb(2), two equivalent Tb(1), and one Sb(1) atom to form distorted OTb3Sb tetrahedra that share corners with two equivalent O(5)Tb3Sb tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra, corners with two equivalent O(4)Tb4 tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(5)Tb3Sb tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra,  an edgeedge with one O(4)Tb4 tetrahedra, and  an edgeedge with one O(1)Tb2Sb2 trigonal pyramid.
Tb3SbO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Sb(1)O6 octahedra,  a cornercorner with one Tb(1)O7 pentagonal bipyramid, edges with two equivalent Sb(1)O6 octahedra, and edges with three equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 45-48°. The Tb(1)-O(1) bond length is 2.48 Å. The Tb(1)-O(2) bond length is 2.23 Å. The Tb(1)-O(4) bond length is 2.29 Å. There is one shorter (2.30 Å) and one longer (2.43 Å) Tb(1)-O(3) bond length. There is one shorter (2.30 Å) and one longer (2.44 Å) Tb(1)-O(5) bond length. In the second Tb site, Tb(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Tb(2)-O(2) bond lengths are 2.39 Å. Both Tb(2)-O(3) bond lengths are 2.79 Å. Both Tb(2)-O(4) bond lengths are 2.34 Å. Both Tb(2)-O(5) bond lengths are 2.53 Å. Sb(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form SbO6 octahedra that share corners with two equivalent Sb(1)O6 octahedra, corners with four equivalent Tb(1)O7 pentagonal bipyramids, and edges with four equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. Both Sb(1)-O(1) bond lengths are 2.03 Å. Both Sb(1)-O(3) bond lengths are 1.98 Å. Both Sb(1)-O(5) bond lengths are 2.01 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Sb(1) atoms to form distorted OTb2Sb2 trigonal pyramids that share corners with two equivalent O(4)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with two equivalent O(5)Tb3Sb tetrahedra. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(2)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with four equivalent O(4)Tb4 tetrahedra,  an edgeedge with one O(4)Tb4 tetrahedra, edges with two equivalent O(5)Tb3Sb tetrahedra, and  an edgeedge with one O(1)Tb2Sb2 trigonal pyramid. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form OTb4 tetrahedra that share corners with two equivalent O(4)Tb4 tetrahedra, corners with four equivalent O(5)Tb3Sb tetrahedra, corners with four equivalent O(2)Tb4 tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with two equivalent O(5)Tb3Sb tetrahedra. In the fifth O site, O(5) is bonded to one Tb(2), two equivalent Tb(1), and one Sb(1) atom to form distorted OTb3Sb tetrahedra that share corners with two equivalent O(5)Tb3Sb tetrahedra, corners with two equivalent O(2)Tb4 tetrahedra, corners with two equivalent O(4)Tb4 tetrahedra, corners with two equivalent O(1)Tb2Sb2 trigonal pyramids,  an edgeedge with one O(5)Tb3Sb tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra,  an edgeedge with one O(4)Tb4 tetrahedra, and  an edgeedge with one O(1)Tb2Sb2 trigonal pyramid.