Y3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. In the second Y site, Y(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Y(2)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. Ta(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Y(2)O7 pentagonal bipyramids, and edges with four equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Y(1), two equivalent Y(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Y(2) and two equivalent Ta(1) atoms to form distorted OY2Ta2 trigonal pyramids that share corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(2)Y2Ta2 trigonal pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. 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)Y4 tetrahedra, corners with two equivalent O(2)Y2Ta2 trigonal pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(4)Y4 tetrahedra, corners with four equivalent O(3)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, and  an edgeedge with one O(2)Y2Ta2 trigonal pyramid.
Y3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(1) atoms. Both Y(1)-O(3) bond lengths are 2.31 Å. Both Y(1)-O(4) bond lengths are 2.36 Å. All Y(1)-O(1) bond lengths are 2.60 Å. In the second Y site, Y(2) is bonded to one O(2), one O(3), one O(4), and four equivalent O(1) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Y(2)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 46°. The Y(2)-O(2) bond length is 2.46 Å. The Y(2)-O(3) bond length is 2.26 Å. The Y(2)-O(4) bond length is 2.19 Å. There are two shorter (2.27 Å) and two longer (2.41 Å) Y(2)-O(1) bond lengths. Ta(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Y(2)O7 pentagonal bipyramids, and edges with four equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. Both Ta(1)-O(2) bond lengths are 1.99 Å. All Ta(1)-O(1) bond lengths are 1.97 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Y(1), two equivalent Y(2), and one Ta(1) atom. In the second O site, O(2) is bonded to two equivalent Y(2) and two equivalent Ta(1) atoms to form distorted OY2Ta2 trigonal pyramids that share corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(2)Y2Ta2 trigonal pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. 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)Y4 tetrahedra, corners with two equivalent O(2)Y2Ta2 trigonal pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(4)Y4 tetrahedra, corners with four equivalent O(3)Y4 tetrahedra,  an edgeedge with one O(3)Y4 tetrahedra, and  an edgeedge with one O(2)Y2Ta2 trigonal pyramid.