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DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, and edges with six equivalent AlO6 octahedra. There are three shorter (2.02 Å) and three longer (2.07 Å) Mg–O bond lengths. 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 three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with nine equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There is three shorter (1.83 Å) and one longer (1.91 Å) Al–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three equivalent 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 one Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel structured and crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Mg2+ is bonded to four equivalent O2- atoms to form MgO4 tetrahedra that share corners with twelve equivalent AlO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Mg–O bond lengths are 1.96 Å. Al3+ is bonded to six equivalent O2- atoms to form AlO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six equivalent AlO6 octahedra. All Al–O bond lengths are 1.94 Å. O2- is bonded to one Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMgAl3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four equivalent AlO6 octahedra. There are four shorter (2.03 Å) and two longer (2.06 Å) Mg–O bond lengths. 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 six equivalent MgO6 octahedra and corners with six equivalent AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–57°. There is two shorter (1.79 Å) and two longer (1.85 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 six equivalent AlO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent MgO6 octahedra. There is two shorter (1.90 Å) and four longer (1.97 Å) Al–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two Al3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are seven inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.97–2.12 Å. In the second Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.94–2.00 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–60°. There is one shorter (1.95 Å) and three longer (1.96 Å) Mg–O bond length. In the fourth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–61°. There is three shorter (1.97 Å) and one longer (1.98 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 59–60°. All Mg–O bond lengths are 1.96 Å. There are twelve inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with four equivalent MgO6 octahedra and corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 50–59°. There are a spread of Al–O bond distances ranging from 1.79–1.83 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four equivalent AlO4 tetrahedra, edges with two equivalent AlO6 octahedra, and edges with four equivalent MgO6 octahedra. There is two shorter (1.81 Å) and four longer (2.04 Å) Al–O bond length. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–2.00 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, corners with five MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–2.00 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is one shorter (1.93 Å) and five longer (1.94 Å) Al–O bond length. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.93 Å) and three longer (1.94 Å) Al–O bond length. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is two shorter (1.93 Å) and four longer (1.94 Å) Al–O bond length. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six equivalent MgO4 tetrahedra and edges with six AlO6 octahedra. All Al–O bond lengths are 1.94 Å. There are twenty inequivalent O2- sites. In the first O2- site, O2- is bonded in a rectangular see-saw-like geometry to two equivalent Mg2+ and two Al3+ atoms. In the second O2- site, O2- is bonded to three Mg2+ and one Al3+ atom to form distorted corner-sharing OMg3Al tetrahedra. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the fifth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two OMgAl3 tetrahedra, corners with six OMgAl3 trigonal pyramids, edges with two OMgAl3 tetrahedra, and an edgeedge with one OAl4 trigonal pyramid. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to four Al3+ atoms to form a mixture of distorted edge and corner-sharing OAl4 trigonal pyramids. In the tenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eleventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twelfth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 tetrahedra that share corners with two equivalent OMgAl3 tetrahedra, corners with six OMgAl3 trigonal pyramids, edges with two equivalent OMgAl3 tetrahedra, and an edgeedge with one OAl4 trigonal pyramid. In the thirteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fifteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the eighteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the nineteenth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the twentieth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are fourteen inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 52–65°. There are a spread of Mg–O bond distances ranging from 1.92–2.01 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.09 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.92–2.00 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.08 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.91–1.98 Å. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–66°. There are a spread of Mg–O bond distances ranging from 1.97–2.00 Å. In the seventh Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.08 Å. In the eighth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.98 Å) Mg–O bond length. In the tenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.09 Å. In the eleventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with ten AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the twelfth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the thirteenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–61°. There are a spread of Mg–O bond distances ranging from 1.94–2.01 Å. In the fourteenth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with twelve AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–63°. There is three shorter (1.95 Å) and one longer (2.04 Å) Mg–O bond length. There are twenty-one inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–61°. There are a spread of Al–O bond distances ranging from 1.82–1.89 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two AlO4 tetrahedra, corners with four MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.03 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.01 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Al–O bond distances ranging from 1.83–1.89 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.06 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–2.01 Å. In the seventh Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Al–O bond distances ranging from 1.82–1.88 Å. In the eighth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.07 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.08 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–1.98 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.92–1.97 Å. In the thirteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.89–1.98 Å. In the fifteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.97 Å. In the sixteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.99 Å. In the seventeenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–1.96 Å. In the eighteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six MgO4 tetrahedra and edges with six AlO6 octahedra. There is three shorter (1.90 Å) and three longer (1.97 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 two equivalent AlO4 tetrahedra, corners with four MgO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–2.01 Å. In the twentieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, an edgeedge with one MgO6 octahedra, and edges with five AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.83–2.08 Å. In the twenty-first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one MgO6 octahedra and corners with eleven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 53–61°. There are a spread of Al–O bond distances ranging from 1.75–1.88 Å. There are forty-two inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the third O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Al3+ atoms to form distorted OAl4 trigonal pyramids that share corners with nine OMgAl3 trigonal pyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with two equivalent OAl4 trigonal pyramids. In the fifth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form OMgAl3 tetrahedra that share corners with twelve OMgAl3 trigonal pyramids and edges with three OAl4 trigonal pyramids. In the sixth O2- site, O2- is bonded to four Al3+ atoms to form distorted OAl4 trigonal pyramids that share corners with nine OMgAl3 trigonal pyramids, an edgeedge with one OMgAl3 tetrahedra, and edges with two OAl4 trigonal pyramids. In the seventh O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 tetrahedra. In the eighth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted OMgAl3 trigonal pyramids that share corners with three equivalent OMgAl3 tetrahedra, corners with seven OAl4 trigonal pyramids, and edges with three OMgAl3 trigonal pyramids. In the ninth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form a mixture of distorted edge and corner-sharing OMgAl3 trigonal pyramids. In the tenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Mg2+ and two Al3+ atoms. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to one Mg2+ and three Al3+ atoms. In t

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 is Spinel-like structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are fourteen inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.97–2.10 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.95–2.13 Å. In the third Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with four MgO6 octahedra and corners with eight AlO6 octahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Mg–O bond distances ranging from 1.94–1.97 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the fifth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the sixth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There is three shorter (1.93 Å) and one longer (1.96 Å) Mg–O bond length. In the seventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.92–1.97 Å. In the eighth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.06 Å. In the ninth Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.91–1.97 Å. In the tenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the eleventh Mg2+ site, Mg2+ is bonded to four O2- atoms to form MgO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–62°. There are a spread of Mg–O bond distances ranging from 1.93–1.98 Å. In the twelfth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the thirteenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.07 Å. In the fourteenth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AlO4 tetrahedra, and edges with six AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.00–2.06 Å. There are twenty-eight inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with five MgO6 octahedra and corners with seven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Al–O bond distances ranging from 1.78–1.83 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with six AlO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.03 Å. In the third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one MgO4 tetrahedra, corners with five AlO4 tetrahedra, edges with two AlO6 octahedra, and edges with four MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.80–2.05 Å. In the fourth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with three MgO6 octahedra, and edges with three AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the sixth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the seventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the eighth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with five MgO6 octahedra and corners with seven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 54–61°. There are a spread of Al–O bond distances ranging from 1.80–1.87 Å. In the ninth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the tenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the eleventh Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the twelfth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the thirteenth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the fourteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.04 Å. In the fifteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the sixteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.03 Å. In the seventeenth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.91 Å. In the eighteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the nineteenth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the twentieth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the twenty-first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 57–59°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the twenty-second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three MgO4 tetrahedra, corners with three AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.05 Å. In the twenty-third Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent MgO4 tetrahedra, corners with four AlO4 tetrahedra, edges with two equivalent MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.85–2.00 Å. In the twenty-fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with three MgO6 octahedra and corners with nine AlO6 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Al–O bond distances ranging from 1.83–1.90 Å. In the twenty-fifth Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with three equivalent MgO4 tetrahedra, corners with three equivalent AlO4 tetrahedra, edges with two MgO6 octahedra, and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.88–2.02 Å. In the twenty-sixth Al3+ site, Al3+ is bonded to six O2- atoms to

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.04–2.58 Å. 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 0–51°. There are a spread of Al–O bond distances ranging from 1.85–2.00 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form distorted OMg2Al3 trigonal bipyramids that share corners with five equivalent OMg2Al2 tetrahedra, corners with two equivalent OMg2Al3 trigonal bipyramids, an edgeedge with one OMg2Al2 tetrahedra, and edges with five equivalent OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Al3+ atoms to form distorted OMg2Al2 tetrahedra that share corners with two equivalent OMg2Al2 tetrahedra, corners with ten equivalent OMg2Al3 trigonal bipyramids, and edges with two equivalent OMg2Al3 trigonal bipyramids. In the third O2- site, O2- is bonded in a distorted square co-planar geometry to two equivalent Mg2+ and four equivalent Al3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on MgAl2O4 by Materials Project

MgAl2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.17–2.56 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Al–O bond distances ranging from 1.87–1.96 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing AlO6 octahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Al–O bond distances ranging from 1.86–1.97 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Al3 trigonal bipyramids. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms. In the third O2- site, O2- is bonded to two equivalent Mg2+ and three equivalent Al3+ atoms to form a mixture of distorted corner and edge-sharing OMg2Al3 trigonal bipyramids. In the fourth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Mg2+ and three Al3+ atoms.

36 MATERIALS SCIENCE↗
NASA NTRSDate not supplied

Vanadium Valence in MgAl2O4 Spinels at Reducing Conditions (IW to IW-5)

Vanadium is commonly a major or minor element in spinel structured oxides from a wide range of planetary materials [1-3]. Vanadium is stable in multiple valence states of 5+, 4+, 3+, and 2+ in natural systems, and spinel-structured oxides are known to host vanadium in 4+, 3+, and 2+ [4-6]. However, the understanding of 2+ stability at lower fO2 conditions has been hindered by lack of experiments at or below IW-1 conditions [5]. Insufficient experimental data is available due to the difficulty in controlling fO2 at low conditions in general, and the lack of appropriate standards for comparison to natural materials. Our progress on controlling fO2 in high pressure experimental samples has allowed us to create reducing conditions that are appropriate to studying V valence in spinels at fO2 relevant to natural reducing systems [7]. Here we extend this approach to study V in reduced conditions, at high temperatures. After at-tempting shorter durations and lower temperatures, we demonstrated the need for equilibration times > 6 hours at 1600 °C in order to approach equilibrium. Only then can we produce highly equilibrated samples that provide new insights into V valence at low fO2.

oxygen fugacity↗
DOE OSTI2020

Structural and mechanical properties of magnesium aluminate nanoceramics under high pressure

Nanoceramics may have different structural and physical properties compared to their coarse-grained counterparts. Here, we report the high-pressure study of micro- and nano-crystalline MgAl2O4 in order to examine the effect of particle size on the structural stability. A reversible pressure-induced phase transition (cubic to tetragonal) is observed in MgAl2O4 nanocrystals under non-hydrostatic pressure at room temperature, in contrast to the previously reported structural transition of MgAl2O4 at high pressure and high temperature. It is also found that the compressed MgAl2O4 microcrystals do not fracture further below 60 nm, suggesting a plastic deformation mechanism transition. MgAl2O4 with a grain size above ∼60 nm exhibits normal cracking behaviors, but shows metal-like plastic deformation behaviors below this critical size. It is implied that combined ductility and strength can be achieved in nanoceramic MgAl2O4.

Xu, Jianing (ORCID:0000000325474344)↗
DOE OSTI2026

Interfacial magnetization enhancement and the perpendicularly magnetized component in Fe16N2 thin films

A detailed study of depth-resolved magnetization and microstructure of Fe16N2 thin films on MgO (001) and MgAl2O4 (001) substrates and Fe and Cr seed layers is presented. Two aspects of the magnetic properties of Fe16N2 thin films are discussed. First, magnetization enhancement at the interface is observed. Strain and nitrogen deficiency are discussed as possible interfacial mechanisms contributing to this enhancement. Second, the perpendicularly magnetized component (PMC) is identified in Fe16N2 thin films. Correlation with microstructural observations suggests that the PMC is associated with V-shaped grains that are not fully confined within the continuous Fe16N2 layer.

Hang, Xudong [University of Minnesota]↗
DOE OSTI2023

Short Range Order in Disordered Spinel and the Impact on Cation Vacancy Transport

Spinels are important complex oxides for use in radiation damage environments and resulting from the corrosion of steels. It is known that, in these environments, normal spinels exist with some concentration of antisite cation pairs known as inversion. In this work we show that even in highly disordered states characterized by high levels of inversion, spinel still shows some short range order (SRO) that manifests itself in antisite chains. The propensity to form these antisite chains is confirmed through Monte Carlo simulations which find that the length of chains which can form depend on the spinel chemistry. We also consider the effect of antisite chains on the diffusivity of cation vacancies and find the effect strongly depends on the spinel chemistry. At the extremes, chains in FeCr2O4 significantly increase vacancy transport but in MgAl2O4 chains have the inverse effect of drastically reducing vacancy mobility. The explanation of these dramatically different effects results from the assessment of the thermodynamic stability of the antisite chains and contrasting attractive/repulsive interactions of vacancies with the chains.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Anomalous Hall effect and perpendicular magnetic anisotropy in ultrathin ferrimagnetic NiCo2O4 films

The inverse spinel ferrimagnetic NiCo2O4 possesses high magnetic Curie temperature TC, high spin polarization, and strain-tunable magnetic anisotropy. Understanding the thickness scaling limit of these intriguing magnetic properties in NiCo2O4 thin films is critical for their implementation in nanoscale spintronic applications. In this work, we report the unconventional magnetotransport properties of epitaxial (001) NiCo2O4 films on MgAl2O4 substrates in the ultrathin limit. Anomalous Hall effect measurements reveal strong perpendicular magnetic anisotropy for films down to 1.5 unit cell (1.2 nm), while TC for 3 unit cell and thicker films remains above 300 K. The sign change in the anomalous Hall conductivity (σxy) and its scaling relation with the longitudinal conductivity (σxx) can be attributed to the competing effects between impurity scattering and band intrinsic Berry curvature, with the latter vanishing upon the thickness driven metal–insulator transition. Our study reveals the critical role of film thickness in tuning the relative strength of charge correlation, Berry phase effect, spin–orbit interaction, and impurity scattering, providing important material information for designing scalable epitaxial magnetic tunnel junctions and sensing devices using NiCo2O4.

Chen, Xuegang↗
DOE OSTI2022

Site and Structural Requirements for the Dehydra-Decyclization of Cyclic Ethers on ZrO2

In this study, we examined the site and structural requirements for the dehydra-decyclization of cyclic ethers, tetrahydrofuran, and tetrahydropyran to produce conjugated dienes over ZrO2-based catalysts, a reaction that could be an important step in the use of biomass-derived sugars as a starting material to produce monomers for the plastics industry. To help identify the active sites for this reaction, studies were conducted in which ZrO2 surfaces were decorated with Na. These studies showed that Na was effective at poisoning the activity for the ring opening of cyclic ethers, but much less so for the dehydration of the resulting adsorbed alkoxides. The studies of the activity of different types of ZrO2 for the dehydra-decyclization reaction, including single crystals and ultra-thin films supported on MgAl2O4 and silica, also showed that the reaction was dependent on the local structure of the ZrO2 surface. The insights these results provide for identifying the active sites on the ZrO2 surface are discussed.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

A Thermodynamic Investigation of Ni on Thin-Film Titanates (ATiO3)

Thin, ~1-nm films of CaTiO3, SrTiO3, and BaTiO3 were deposited onto MgAl2O4 by Atomic Layer Deposition (ALD) and then studied as catalyst supports for ~5 wt % of Ni that was added to the perovskite thin films by Atomic Layer Deposition. Scanning Transmission Electron Microscopy demonstrated that both the Ni and the perovskites uniformly covered the surface of the support following oxidation at 1073 K, even after redox cycling, but large Ni particles formed following a reduction at 1073 K. When compared to Ni/MgAl2O4, the perovskite-containing catalysts required significantly higher temperatures for Ni reduction. Equilibrium constants for Ni oxidation, as determined from Coulometric Titration, indicated that the oxidation of Ni shifted to lower PO2 on the perovskite-containing materials. Based on Ni equilibrium constants, Ni interactions are strongest with CaTiO3, followed by SrTiO3 and BaTiO3. The shift in the equilibrium constant was shown to cause reversible deactivation of the Ni/CaTiO3/MgAl2O4 catalyst for CO2 reforming of CH4 at high CO2 pressures, due to the oxidation of the Ni.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1972

Chromian spinels from Apollo 14 rocks.

Results of electron microprobe analysis of 13 pink, isotropic, high-relief grains from Apollo 14 elastic rock 14063,14 and a lithic fragment from the 1 to 2 mm fines, 14002,7, identifying them as spinel minerals dominated by the spinel component MgAl2O4 associated with a moderate content of chromite and hercynite. The spinel is thought to have crystallized from a magma high in aluminum and low in iron, with possible crystal separation, followed by incorporation in clastic rocks by impacts. Many bulk compositions of the elastic fragments fall near the field of primary spinel in the model system An-Fo-SiO2. Experimental syntheses of Apollo 14 rocks are needed to test the suggested primary origin.

Steele, I. M.↗
NASA NTRS1973

Luna 20 soil - Abundance and composition of phases in the 45-125 micron fraction.

Glass compositions in the Luna 20 soil indicate a minor contribution of mare rocks and a major contribution of highly feldspathic highland material. Glasses with the composition of highland basalt (anorthositic gabbro or norite) predominate in a range of highly aluminous glasses. The analyses of minerals in the soil show that the highland rocks have a unique assemblage of minerals that can readily be distinguished from the mineral assemblages of either mare or KREEP basalts. The soils are characterized by abundant anorthitic, low-Fe plagioclase. Highly magnesian orthopyroxenes, pigeonites, and augites are the most prominent pyroxenes. Unlike mare basalt pyroxenes, clinopyroxenes with intermediate Ca values are not abundant, but extreme iron enrichment toward pyroxferroite does occur. Olivines are more abundant than at other sites and are Mg-rich, low in Ca and Cr. Spinels with compositions approaching MgAl2O4 predominate over pleonastes and chromites. Ilmenite and metal are present but not abundant. The mineral compositions are consistent with derivation from a suite of highly feldspathic rocks in which highland basalt compositions predominate.

Reid, A. M.↗