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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on KNaGdNbO5 by Materials Project

KNaGdNbO5 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. K1+ is bonded in a distorted square co-planar geometry to four equivalent O2- atoms. All K–O bond lengths are 2.88 Å. Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share corners with five equivalent NbO5 trigonal bipyramids. There are four shorter (2.30 Å) and one longer (2.34 Å) Na–O bond lengths. Gd3+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Gd–O bond lengths are 2.45 Å. Nb5+ is bonded to five O2- atoms to form distorted NbO5 trigonal bipyramids that share corners with five equivalent NaO5 trigonal bipyramids. There is one shorter (1.88 Å) and four longer (1.98 Å) Nb–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent K1+, one Na1+, and one Nb5+ atom to form distorted OK4NaNb octahedra that share corners with four equivalent OK4NaNb octahedra, corners with eight equivalent ONaGd2Nb tetrahedra, and edges with four equivalent OK4NaNb octahedra. The corner-sharing octahedral tilt angles are 12°. In the second O2- site, O2- is bonded to one Na1+, two equivalent Gd3+, and one Nb5+ atom to form distorted ONaGd2Nb tetrahedra that share corners with two equivalent OK4NaNb octahedra, corners with ten equivalent ONaGd2Nb tetrahedra, and edges with five equivalent ONaGd2Nb tetrahedra. The corner-sharing octahedra tilt angles range from 70–72°.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on K2Na2Gd4Nb2O13 by Materials Project

K2Na2Gd4Nb2O13 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K1+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.81–3.30 Å. Na1+ is bonded to five O2- atoms to form distorted NaO5 trigonal bipyramids that share corners with five equivalent NbO5 trigonal bipyramids and edges with two equivalent GdO7 pentagonal bipyramids. There are a spread of Na–O bond distances ranging from 2.27–2.33 Å. There are two inequivalent Gd3+ sites. In the first Gd3+ site, Gd3+ is bonded to seven O2- atoms to form distorted GdO7 pentagonal bipyramids that share a cornercorner with one GdO7 pentagonal bipyramid, an edgeedge with one GdO7 pentagonal bipyramid, edges with two equivalent NaO5 trigonal bipyramids, and edges with two equivalent NbO5 trigonal bipyramids. There are a spread of Gd–O bond distances ranging from 2.36–2.47 Å. In the second Gd3+ site, Gd3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Gd–O bond distances ranging from 2.34–2.57 Å. Nb5+ is bonded to five O2- atoms to form NbO5 trigonal bipyramids that share corners with five equivalent NaO5 trigonal bipyramids and edges with two equivalent GdO7 pentagonal bipyramids. There are a spread of Nb–O bond distances ranging from 1.87–2.02 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to four Gd3+ atoms to form distorted OGd4 tetrahedra that share corners with eight ONaGd2Nb tetrahedra and edges with two equivalent OGd4 tetrahedra. In the second O2- site, O2- is bonded in a 6-coordinate geometry to four equivalent K1+, one Na1+, and one Nb5+ atom. In the third O2- site, O2- is bonded to four Gd3+ atoms to form a mixture of edge and corner-sharing OGd4 tetrahedra. In the fourth O2- site, O2- is bonded in a 6-coordinate geometry to two equivalent K1+, one Na1+, two Gd3+, and one Nb5+ atom. In the fifth O2- site, O2- is bonded to one Na1+, two Gd3+, and one Nb5+ atom to form distorted corner-sharing ONaGd2Nb tetrahedra. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+, one Na1+, two Gd3+, and one Nb5+ atom. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+, one Na1+, two Gd3+, and one Nb5+ atom.

36 MATERIALS SCIENCE↗