Dy3TaO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(4) atoms. In the second Dy site, Dy(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted DyO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Dy(2)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Dy(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 34-45°. Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Dy(2)O7 pentagonal bipyramids, and edges with four equivalent Dy(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Dy(1), two equivalent Dy(2), and one Ta(1) atom to form distorted ODy3Ta tetrahedra that share corners with four equivalent O(4)Dy4 tetrahedra, edges with two equivalent O(1)Dy3Ta tetrahedra, and edges with two equivalent O(4)Dy4 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Dy(2) and one Ta(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Dy(2) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Dy(1) and two equivalent Dy(2) atoms to form ODy4 tetrahedra that share corners with four equivalent O(1)Dy3Ta tetrahedra, corners with six equivalent O(4)Dy4 tetrahedra,  an edgeedge with one O(4)Dy4 tetrahedra, and edges with two equivalent O(1)Dy3Ta tetrahedra.
Dy3TaO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded in a 6-coordinate geometry to two equivalent O(1) and four equivalent O(4) atoms. Both Dy(1)-O(1) bond lengths are 2.31 Å. There are two shorter (2.34 Å) and two longer (2.40 Å) Dy(1)-O(4) bond lengths. In the second Dy site, Dy(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted DyO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Dy(2)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Dy(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 34-45°. The Dy(2)-O(3) bond length is 2.63 Å. There is one shorter (2.30 Å) and one longer (2.42 Å) Dy(2)-O(1) bond length. There is one shorter (2.27 Å) and one longer (2.38 Å) Dy(2)-O(2) bond length. There is one shorter (2.25 Å) and one longer (2.30 Å) Dy(2)-O(4) bond length. Ta(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Dy(2)O7 pentagonal bipyramids, and edges with four equivalent Dy(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 38°. Both Ta(1)-O(1) bond lengths are 2.05 Å. Both Ta(1)-O(2) bond lengths are 1.94 Å. There is one shorter (1.95 Å) and one longer (2.00 Å) Ta(1)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Dy(1), two equivalent Dy(2), and one Ta(1) atom to form distorted ODy3Ta tetrahedra that share corners with four equivalent O(4)Dy4 tetrahedra, edges with two equivalent O(1)Dy3Ta tetrahedra, and edges with two equivalent O(4)Dy4 tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to two equivalent Dy(2) and one Ta(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Dy(2) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Dy(1) and two equivalent Dy(2) atoms to form ODy4 tetrahedra that share corners with four equivalent O(1)Dy3Ta tetrahedra, corners with six equivalent O(4)Dy4 tetrahedra,  an edgeedge with one O(4)Dy4 tetrahedra, and edges with two equivalent O(1)Dy3Ta tetrahedra.