Y3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Y(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Y(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 40-50°. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Ta(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Y(1)O7 pentagonal bipyramids, and edges with four equivalent Y(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Ta(1) atoms to form distorted OY2Ta2 trigonal pyramids that share corners with two equivalent O(3)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(2)Y4 tetrahedra, and edges with two equivalent O(4)Y3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(2)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with four equivalent O(3)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, edges with two equivalent O(4)Y3Ta tetrahedra, and  an edgeedge with one O(1)Y2Ta2 trigonal pyramid. In the third O site, O(3) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(3)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with four equivalent O(2)Y4 tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(2)Y4 tetrahedra, and edges with two equivalent O(4)Y3Ta tetrahedra. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Y(1), and one Ta(1) atom to form distorted OY3Ta tetrahedra that share corners with two equivalent O(4)Y3Ta tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(4)Y3Ta tetrahedra,  an edgeedge with one O(2)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, and  an edgeedge with one O(1)Y2Ta2 trigonal pyramid. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Y(2), two equivalent Y(1), and one Ta(1) atom.
Y3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(1), one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Y(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Y(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 40-50°. The Y(1)-O(1) bond length is 2.46 Å. The Y(1)-O(2) bond length is 2.20 Å. The Y(1)-O(3) bond length is 2.28 Å. There is one shorter (2.27 Å) and one longer (2.40 Å) Y(1)-O(4) bond length. There is one shorter (2.26 Å) and one longer (2.41 Å) Y(1)-O(5) bond length. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Y(2)-O(2) bond lengths are 2.38 Å. Both Y(2)-O(3) bond lengths are 2.31 Å. Both Y(2)-O(4) bond lengths are 2.37 Å. Both Y(2)-O(5) bond lengths are 2.97 Å. Ta(1) is bonded to two equivalent O(1), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Y(1)O7 pentagonal bipyramids, and edges with four equivalent Y(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. Both Ta(1)-O(1) bond lengths are 1.99 Å. Both Ta(1)-O(4) bond lengths are 2.02 Å. Both Ta(1)-O(5) bond lengths are 1.93 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and two equivalent Ta(1) atoms to form distorted OY2Ta2 trigonal pyramids that share corners with two equivalent O(3)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(2)Y4 tetrahedra, and edges with two equivalent O(4)Y3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(2)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with four equivalent O(3)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, edges with two equivalent O(4)Y3Ta tetrahedra, and  an edgeedge with one O(1)Y2Ta2 trigonal pyramid. In the third O site, O(3) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(3)Y4 tetrahedra, corners with four equivalent O(4)Y3Ta tetrahedra, corners with four equivalent O(2)Y4 tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(2)Y4 tetrahedra, and edges with two equivalent O(4)Y3Ta tetrahedra. In the fourth O site, O(4) is bonded to one Y(2), two equivalent Y(1), and one Ta(1) atom to form distorted OY3Ta tetrahedra that share corners with two equivalent O(4)Y3Ta tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(1)Y2Ta2 trigonal pyramids,  an edgeedge with one O(4)Y3Ta tetrahedra,  an edgeedge with one O(2)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, and  an edgeedge with one O(1)Y2Ta2 trigonal pyramid. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Y(2), two equivalent Y(1), and one Ta(1) atom.