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DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are sixteen inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Al–O bond distances ranging from 1.72–1.86 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent AlO6 octahedra, corners with two equivalent AlO4 tetrahedra, a cornercorner with one AlO4 trigonal pyramid, and edges with six AlO6 octahedra. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form edge-sharing AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.79–2.06 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, a cornercorner with one AlO4 trigonal pyramid, and edges with seven AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–1.94 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, a cornercorner with one AlO4 trigonal pyramid, and edges with seven AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.99 Å. In the sixth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of Al–O bond distances ranging from 1.79–1.85 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form distorted AlO6 octahedra that share corners with three AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.80–2.13 Å. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.08 Å. In the ninth Al3+ site, Al3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.79–2.41 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 6–12°. There are a spread of Al–O bond distances ranging from 1.82–2.11 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form distorted AlO6 octahedra that share corners with three AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.79–2.32 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO4 tetrahedra, corners with two equivalent AlO4 trigonal pyramids, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.05 Å. In the thirteenth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–65°. There are a spread of Al–O bond distances ranging from 1.78–1.85 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four AlO4 tetrahedra, corners with two equivalent AlO4 trigonal pyramids, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.02 Å. In the fifteenth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 trigonal pyramids. The corner-sharing octahedra tilt angles range from 40–67°. There are a spread of Al–O bond distances ranging from 1.74–2.03 Å. In the sixteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent AlO4 tetrahedra, corners with three equivalent AlO4 trigonal pyramids, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.78–2.11 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the fifth O2- site, O2- is bonded to five Al3+ atoms to form edge-sharing OAl5 square pyramids. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to three Al3+ atoms. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the twelfth O2- site, O2- is bonded to five Al3+ atoms to form distorted edge-sharing OAl5 square pyramids. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted trigonal pyramidal geometry to four Al3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the twentieth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted T-shaped geometry to three Al3+ atoms. In the twenty-second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with seven equivalent AlO6 octahedra and corners with two equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.77 Å) and one longer (1.81 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with seven equivalent AlO4 tetrahedra and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.02 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are ten inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with six AlO6 octahedra, corners with two equivalent AlO5 square pyramids, and an edgeedge with one AlO5 square pyramid. The corner-sharing octahedra tilt angles range from 14–71°. There are a spread of Al–O bond distances ranging from 1.75–1.84 Å. In the second Al3+ site, Al3+ is bonded to five O2- atoms to form distorted AlO5 square pyramids that share corners with six AlO6 octahedra, a cornercorner with one AlO5 square pyramid, corners with two equivalent AlO4 tetrahedra, and an edgeedge with one AlO6 octahedra. The corner-sharing octahedra tilt angles range from 47–54°. There are a spread of Al–O bond distances ranging from 1.81–2.01 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra, an edgeedge with one AlO6 octahedra, and edges with three AlO5 square pyramids. There are a spread of Al–O bond distances ranging from 1.86–2.23 Å. In the fourth Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 square pyramids that share a cornercorner with one AlO5 square pyramid, corners with three AlO4 tetrahedra, edges with three AlO6 octahedra, and an edgeedge with one AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.82–1.93 Å. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with ten AlO6 octahedra and a cornercorner with one AlO5 square pyramid. The corner-sharing octahedra tilt angles range from 55–62°. There are a spread of Al–O bond distances ranging from 1.80–1.84 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO5 square pyramids, corners with four AlO4 tetrahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.82–2.00 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra, edges with four AlO6 octahedra, and an edgeedge with one AlO5 square pyramid. There are a spread of Al–O bond distances ranging from 1.83–2.06 Å. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with eight AlO6 octahedra and corners with two equivalent AlO5 square pyramids. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.76–1.84 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO5 square pyramids, corners with four AlO4 tetrahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.82–2.07 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO5 square pyramids, corners with four AlO4 tetrahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.01 Å. There are fifteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fourth O2- site, O2- is bonded in a T-shaped geometry to three Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the thirteenth O2- site, O2- is bonded in a tetrahedral geometry to four Al3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the fifteenth O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.69–1.82 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with four equivalent AlO4 tetrahedra, an edgeedge with one AlO4 tetrahedra, and edges with two equivalent AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.82–2.02 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent AlO4 tetrahedra, corners with four equivalent AlO5 trigonal bipyramids, and an edgeedge with one AlO5 trigonal bipyramid. There are a spread of Al–O bond distances ranging from 1.76–1.79 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 is Corundum-like structured and crystallizes in the trigonal R-3 space group. The structure is three-dimensional. there are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 43°. All Al–O bond lengths are 1.93 Å. In the second Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of corner and face-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 43–53°. All Al–O bond lengths are 1.94 Å. In the third Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of distorted edge, corner, and face-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 53°. There is three shorter (1.85 Å) and three longer (2.03 Å) Al–O bond length. O2- is bonded to four Al3+ atoms to form a mixture of edge and corner-sharing OAl4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form distorted AlO4 tetrahedra that share corners with two equivalent AlO4 tetrahedra, corners with four equivalent AlO5 trigonal bipyramids, and an edgeedge with one AlO4 tetrahedra. There is three shorter (1.80 Å) and one longer (1.83 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with four equivalent AlO4 tetrahedra, corners with two equivalent AlO5 trigonal bipyramids, and edges with two equivalent AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.79–1.96 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to three equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to five O2- atoms to form corner-sharing AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.82–2.00 Å. In the second Al3+ site, Al3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.81–2.26 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 is Corundum-like structured and crystallizes in the trigonal P-31c space group. The structure is three-dimensional. there are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of distorted corner, edge, and face-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 53°. There is three shorter (1.85 Å) and three longer (2.01 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of corner and face-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 44–53°. All Al–O bond lengths are 1.94 Å. In the third Al3+ site, Al3+ is bonded to six equivalent O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 44°. All Al–O bond lengths are 1.94 Å. O2- is bonded to four Al3+ atoms to form a mixture of corner and edge-sharing OAl4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent AlO5 trigonal bipyramids and edges with six equivalent AlO6 octahedra. There is three shorter (1.98 Å) and three longer (2.01 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with six equivalent AlO6 octahedra and corners with six equivalent AlO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 61–62°. There are a spread of Al–O bond distances ranging from 1.75–1.98 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to three equivalent Al3+ atoms. In the second O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 tetrahedra. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of edge and corner-sharing OAl4 tetrahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 is beta indium sulfide-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are thirty-two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is two shorter (1.77 Å) and two longer (1.85 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.77–1.87 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–2.05 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–1.99 Å. In the fifth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Al–O bond distances ranging from 1.76–1.85 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.03 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–1.98 Å. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.76–1.83 Å. In the ninth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.77–1.86 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–1.95 Å. In the eleventh Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.76–1.84 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.05 Å. In the thirteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.06 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.06 Å. In the fifteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.04 Å. In the sixteenth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.77–1.86 Å. In the seventeenth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.76–1.83 Å. In the eighteenth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–61°. There is two shorter (1.77 Å) and two longer (1.85 Å) Al–O bond length. In the nineteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–1.99 Å. In the twentieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–1.99 Å. In the twenty-first Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.76–1.86 Å. In the twenty-second Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Al–O bond distances ranging from 1.76–1.86 Å. In the twenty-third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–1.94 Å. In the twenty-fourth Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 51–60°. There are a spread of Al–O bond distances ranging from 1.76–1.84 Å. In the twenty-fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.05 Å. In the twenty-sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.04 Å. In the twenty-seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.84–1.98 Å. In the twenty-eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–1.93 Å. In the twenty-ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.90–1.95 Å. In the thirtieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–1.98 Å. In the thirty-first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–1.98 Å. In the thirty-second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–1.98 Å. There are forty-eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the eleventh O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the thirteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the fourteenth O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the sixteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the seventeenth O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the nineteenth O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the twentieth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-second O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the twenty-third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the twenty-seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the twenty-eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the twenty-ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the thirtieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the thirty-first O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the thirty-second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the thirty-third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the thirty-fourth O2- site, O2- is bonded to four Al3+ atoms to form distorted edge-sharing OAl4 trigonal pyramids. In the thirty-fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the thirty-sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the thirty-seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the thirty-eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the thirty-ninth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Al3+ atoms. In the fortieth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Al3+ atoms. In the forty-first O2- site, O2- is bonded in a distorted trigonal planar geometry to three Al3+ atoms. In the forty-second O2- site, O2- is bonded in

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 is Corundum-like structured and crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. there are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of face, edge, and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 47–61°. There are a spread of Al–O bond distances ranging from 1.85–1.99 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of face, edge, and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 48–70°. There are a spread of Al–O bond distances ranging from 1.88–2.05 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 tetrahedra. In the second O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al2O3 by Materials Project

Al2O3 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. there are six inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 19°. There are a spread of Al–O bond distances ranging from 1.86–1.97 Å. In the second Al3+ site, Al3+ is bonded in a 4-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.78–2.42 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 19–52°. There are a spread of Al–O bond distances ranging from 1.93–1.97 Å. In the fourth Al3+ site, Al3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.79–2.41 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing AlO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are a spread of Al–O bond distances ranging from 1.79–2.01 Å. In the sixth Al3+ site, Al3+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Al–O bond distances ranging from 1.78–2.30 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to five Al3+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the third O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Al3+ atoms to form a mixture of edge and corner-sharing OAl4 trigonal pyramids. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to three Al3+ atoms. In the sixth O2- site, O2- is bonded in a 5-coordinate geometry to five Al3+ atoms. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to five Al3+ atoms. In the eighth O2- site, O2- is bonded in a trigonal non-coplanar geometry to three Al3+ atoms. In the ninth O2- site, O2- is bonded to four Al3+ atoms to form a mixture of edge and corner-sharing OAl4 trigonal pyramids.

36 MATERIALS SCIENCE↗
NASA NTRS2016

Thermochemistry of CaO-MgO-Al2O3-SiO2 (CMAS) and Advanced Thermal and Environmental Barrier Coating Systems

CaO-MgO-Al2O3-SiO2 (CMAS) oxides are constituents in a broad number of materials and minerals which have recently inferred to discussions in materials science, planetary science, geochemistry and cosmochemistry communities. In materials science, there is increasing interest in the degradation studies of thermal (TBC) and environmental (EBC) barrier coatings of gas turbines by molten CMAS. These coatings have been explored to be applied on silicon-based ceramics and composites which are lighter and more temperature capable hot-section materials of gas turbines than the current Ni-based superalloys. The degradation of the coatings occurs when CMAS minerals carried by the intake air into gas turbines, e.g. in aircraft engines, reacts at high temperatures (1000C) with the coating materials. This causes premature failure of the static and rotating components of the turbine engines. We discuss some preliminary results of the reactions between CMAS and Rare-Earth (RE Y, Yb and Gd) oxide stabilized ZrO2 systems, and stability of the resulting oxides and silicates.

CaO-MgO-Al2O3-SiO2 (CMAS)↗
NASA NTRS1975

Studies on the Al2O3-Ti-Mo-Au metallization system

The behavior of Ti-Mo-Au metallization on Al2O3 and C has been investigated by backscattering spectrometry. Results show that Mo-Au bimetal films typically mix during deposition. Diffusion of Ti in Mo film occurs at 600 C, but is inhibited by the presence of oxygen in the Ti film. Even 1000 A of Mo is not a barrier against interdiffusion of Ti and Au during 20-min anneals at 600 C. The amount of mixing observed also depends on the nature of the substrate which supports the Ti-Mo-Au metallization.

Harris, J. M.↗
NASA NTRS1976

Microstructure of hot-pressed Al2O3-Si3N4 mixtures as a function of holding temperature

Powder mixtures of 40 m/o Si3N4-60 m/o Al2O3 were hot-pressed at 4000 psi at various holding temperatures from 1100 C to 1700 C. Scanning Electron Microscopy and Transmission Electro Microscopy results were correlated to X-ray phase analysis and density measurements. The progressively developed microstructure was used to interpret the densification behavior of SiAlON. Photomicrographs of microstructures are shown.

Yeh, H. C.↗
NASA NTRS1977

Al2O3 half-wave films for long-life CW lasers

Long-term operating-life data are reported for (AlGa)As CW laser diodes. The use of half-wave Al2O3 facet coatings is shown to eliminate facet erosion, allowing stable diode operation at constant current for periods in excess of 10,000 h.

Ladany, I.↗
NASA NTRS1977

Microstructure of hot-pressed Al2O3-Si3N4 mixtures as a function of holding temperature

Powder mixtures of 40 m/o Si3N4-60 m/o Al2O3 were hot-pressed at 4000 psi at various holding temperatures from 1100 C to 1700 C. Scanning and transmission electron microscopy results were correlated to X-ray phase analysis and density measurements. The progressively developed microstructure was used to interpret the densification behavior of SiAlON.

Yeh, H. C.↗