DOE OSTI2020
ErBO3 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. there are two inequivalent Er3+ sites. In the first Er3+ site, Er3+ is bonded to eight O2- atoms to form ErO8 hexagonal bipyramids that share corners with two equivalent ErO8 hexagonal bipyramids, corners with two equivalent BO4 tetrahedra, edges with six equivalent ErO8 hexagonal bipyramids, and edges with four BO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.25–2.45 Å. In the second Er3+ site, Er3+ is bonded to eight O2- atoms to form distorted ErO8 hexagonal bipyramids that share corners with two ErO8 hexagonal bipyramids, corners with two BO4 tetrahedra, edges with six ErO8 hexagonal bipyramids, and edges with four BO4 tetrahedra. There are a spread of Er–O bond distances ranging from 2.23–2.45 Å. There are two inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with two ErO8 hexagonal bipyramids, corners with two BO4 tetrahedra, and edges with four ErO8 hexagonal bipyramids. There are a spread of B–O bond distances ranging from 1.45–1.52 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form BO4 tetrahedra that share corners with two equivalent ErO8 hexagonal bipyramids, corners with two equivalent BO4 tetrahedra, and edges with four ErO8 hexagonal bipyramids. There is two shorter (1.44 Å) and two longer (1.51 Å) B–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to three Er3+ and one B3+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Er3+ and two B3+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Er3+ and two equivalent B3+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Er3+ and one B3+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to three Er3+ and one B3+ atom.