DOE OSTI2020
Dy3TaO7 crystallizes in the orthorhombic C222_1 space group. The structure is three-dimensional. there are two inequivalent Dy3+ sites. In the first Dy3+ site, Dy3+ is bonded to seven O2- atoms to form distorted DyO7 pentagonal bipyramids that share corners with two equivalent TaO6 octahedra, a cornercorner with one DyO7 pentagonal bipyramid, edges with two equivalent TaO6 octahedra, and edges with three equivalent DyO7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 42–48°. There are a spread of Dy–O bond distances ranging from 2.22–2.47 Å. In the second Dy3+ site, Dy3+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Dy–O bond distances ranging from 2.33–2.88 Å. Ta5+ is bonded to six O2- atoms to form TaO6 octahedra that share corners with two equivalent TaO6 octahedra, corners with four equivalent DyO7 pentagonal bipyramids, and edges with four equivalent DyO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 42°. There are a spread of Ta–O bond distances ranging from 1.96–2.03 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Dy3+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded to four Dy3+ atoms to form a mixture of corner and edge-sharing ODy4 tetrahedra. In the third O2- site, O2- is bonded in a 3-coordinate geometry to three Dy3+ and one Ta5+ atom. In the fourth O2- site, O2- is bonded to four Dy3+ atoms to form a mixture of corner and edge-sharing ODy4 tetrahedra. In the fifth O2- site, O2- is bonded to three Dy3+ and one Ta5+ atom to form a mixture of distorted corner and edge-sharing ODy3Ta tetrahedra.