DOE OSTI2020
NaGd3Ti2(SbO7)2 crystallizes in the monoclinic P2/c space group. The structure is three-dimensional. Na1+ is bonded to eight O2- atoms to form distorted NaO8 hexagonal bipyramids that share edges with six GdO8 hexagonal bipyramids, edges with two equivalent TiO6 octahedra, and edges with four SbO6 octahedra. There are a spread of Na–O bond distances ranging from 2.34–2.70 Å. There are three inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent NaO8 hexagonal bipyramids, edges with four GdO8 hexagonal bipyramids, edges with two equivalent SbO6 octahedra, and edges with four TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.72 Å. In the second Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent NaO8 hexagonal bipyramids, edges with four GdO8 hexagonal bipyramids, edges with two equivalent TiO6 octahedra, and edges with four SbO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.59 Å. In the third Gd3+ site, Gd3+ is bonded to eight O2- atoms to form distorted GdO8 hexagonal bipyramids that share edges with two equivalent NaO8 hexagonal bipyramids, edges with four GdO8 hexagonal bipyramids, edges with two equivalent SbO6 octahedra, and edges with four TiO6 octahedra. There are a spread of Gd–O bond distances ranging from 2.22–2.61 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with four SbO6 octahedra, and edges with six GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–47°. There is two shorter (1.95 Å) and four longer (1.99 Å) Ti–O bond length. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra, corners with four SbO6 octahedra, edges with two equivalent NaO8 hexagonal bipyramids, and edges with four GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–45°. There are a spread of Ti–O bond distances ranging from 1.94–2.02 Å. There are two inequivalent Sb5+ sites. In the first Sb5+ site, Sb5+ is bonded to six O2- atoms to form SbO6 octahedra that share corners with two equivalent SbO6 octahedra, corners with four TiO6 octahedra, edges with two equivalent NaO8 hexagonal bipyramids, and edges with four GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 45–48°. There are a spread of Sb–O bond distances ranging from 1.99–2.02 Å. In the second Sb5+ site, Sb5+ is bonded to six O2- atoms to form SbO6 octahedra that share corners with two equivalent SbO6 octahedra, corners with four TiO6 octahedra, edges with two equivalent NaO8 hexagonal bipyramids, and edges with four GdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 45–48°. There are a spread of Sb–O bond distances ranging from 1.98–2.03 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to one Na1+ and three Gd3+ atoms to form ONaGd3 tetrahedra that share corners with six ONaGd3 tetrahedra and an edgeedge with one ONaGdSb2 tetrahedra. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Gd3+ and two Ti4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Gd3+, one Ti4+, and one Sb5+ atom. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+, one Ti4+, and one Sb5+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Gd3+, one Ti4+, and one Sb5+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Na1+, one Gd3+, one Ti4+, and one Sb5+ atom. In the seventh O2- site, O2- is bonded to one Na1+, one Gd3+, and two Sb5+ atoms to form a mixture of distorted edge and corner-sharing ONaGdSb2 tetrahedra.