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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Y2Hf2O7 by Materials Project

Y2Hf2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Y3+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are two shorter (2.28 Å) and six longer (2.53 Å) Y–O bond lengths. Hf4+ is bonded to six equivalent O2- atoms to form corner-sharing HfO6 octahedra. The corner-sharing octahedral tilt angles are 53°. All Hf–O bond lengths are 2.08 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Hf4+ atoms to form a mixture of distorted edge and corner-sharing OY2Hf2 tetrahedra. In the second O2- site, O2- is bonded to four equivalent Y3+ atoms to form a mixture of edge and corner-sharing OY4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Hf2O7 by Materials Project

Y2Hf2O7 crystallizes in the tetragonal P4_12_12 space group. The structure is three-dimensional. Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.21–2.58 Å. Hf4+ is bonded to five O2- atoms to form a mixture of distorted edge and corner-sharing HfO5 trigonal bipyramids. There are a spread of Hf–O bond distances ranging from 1.98–2.27 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Y3+ and two equivalent Hf4+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Y3+ and one Hf4+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Y3+ and one Hf4+ atom. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Hf4+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Y2Hf2O7 by Materials Project

Y2Hf2O7 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Y3+ is bonded to six O2- atoms to form distorted YO6 pentagonal pyramids that share corners with four equivalent HfO5 trigonal bipyramids, edges with three equivalent YO6 pentagonal pyramids, and edges with two equivalent HfO5 trigonal bipyramids. There are a spread of Y–O bond distances ranging from 2.22–2.37 Å. Hf4+ is bonded to five O2- atoms to form distorted HfO5 trigonal bipyramids that share corners with four equivalent YO6 pentagonal pyramids, a cornercorner with one HfO5 trigonal bipyramid, edges with two equivalent YO6 pentagonal pyramids, and an edgeedge with one HfO5 trigonal bipyramid. There are a spread of Hf–O bond distances ranging from 1.95–2.32 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two equivalent Y3+ and one Hf4+ atom. In the second O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Hf4+ atoms to form distorted edge-sharing OY2Hf2 trigonal pyramids. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Hf4+ atoms.

36 MATERIALS SCIENCE↗