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DOE OSTI2021

Structure of triple perovskite BaSr 2 MgTa 2 O 9 revisited

An experimental investigation of the structure and crystal-chemistry of the triple perovskite BaSr 2 MgTa 2 O 9 is reported. Polycrystalline BaSr 2 MgTa 2 O 9 was synthesized via solid-state reaction and its structure quantitatively probed at 10 and 300 K using neutron diffraction. Monoclinic (A2/m, a 0 $\bar{b}$ – $b$ – ) and trigonal structural models (P$\bar{3}$c1, a – a – a – ) were fit to diffraction data. The former was found to correctly reproduce experimental intensities, while the latter failed to do so. This difference is attributed to the ability of the monoclinic model to accurately reflect octahedral tilting. BaSr 2 MgTa 2 O 9 features corner-sharing MgO 6 and TaO 6 octahedra with barium and strontium cations occupying cubooctahedral holes. Barium and strontium are disordered over the A site, whereas B site cations magnesium and tantalum are ordered. Finally, chemical substitution of strontium for barium in Ba 3 MgTa 2 O 9 induces tilting of MgO 6 and TaO 6 octahedra in two directions and geometric distortions of MgO 6 octahedra.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗

DOE OSTI2020

Materials Data on BaSr(MoO3)2 by Materials Project

BaSr(MoO3)2 is (Cubic) Perovskite-derived structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Ba2+ is bonded to twelve equivalent O2- atoms to form BaO12 cuboctahedra that share corners with twelve equivalent BaO12 cuboctahedra, faces with six equivalent SrO12 cuboctahedra, and faces with eight equivalent MoO6 octahedra. All Ba–O bond lengths are 2.91 Å. Sr2+ is bonded to twelve equivalent O2- atoms to form SrO12 cuboctahedra that share corners with twelve equivalent SrO12 cuboctahedra, faces with six equivalent BaO12 cuboctahedra, and faces with eight equivalent MoO6 octahedra. All Sr–O bond lengths are 2.91 Å. Mo4+ is bonded to six equivalent O2- atoms to form MoO6 octahedra that share corners with six equivalent MoO6 octahedra, faces with four equivalent BaO12 cuboctahedra, and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. All Mo–O bond lengths are 2.06 Å. O2- is bonded to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Mo4+ atoms to form a mixture of distorted edge, face, and corner-sharing OBa2Sr2Mo2 octahedra. The corner-sharing octahedra tilt angles range from 0–60°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(PbO3)2 by Materials Project

BaSr(PbO3)2 is Orthorhombic Perovskite-derived structured and crystallizes in the orthorhombic Pmc2_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.66–3.14 Å. Sr2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–2.95 Å. Pb4+ is bonded to six O2- atoms to form corner-sharing PbO6 octahedra. The corner-sharing octahedra tilt angles range from 22–34°. There are a spread of Pb–O bond distances ranging from 2.20–2.25 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to one Ba2+, two equivalent Sr2+, and two equivalent Pb4+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Ba2+, one Sr2+, and two equivalent Pb4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+ and two equivalent Pb4+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Sr2+ and two equivalent Pb4+ atoms to form distorted corner-sharing OSr2Pb2 tetrahedra.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(FeO3)2 by Materials Project

BaSr(FeO3)2 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba is bonded to twelve O atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, corners with eight equivalent SrO12 cuboctahedra, faces with two equivalent SrO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight equivalent FeO6 octahedra. There are four shorter (2.81 Å) and eight longer (2.87 Å) Ba–O bond lengths. Sr is bonded to twelve O atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, corners with eight equivalent BaO12 cuboctahedra, faces with two equivalent BaO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent FeO6 octahedra. There are eight shorter (2.75 Å) and four longer (2.81 Å) Sr–O bond lengths. Fe is bonded to six O atoms to form FeO6 octahedra that share corners with six equivalent FeO6 octahedra, faces with four equivalent BaO12 cuboctahedra, and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–3°. There are a spread of Fe–O bond distances ranging from 1.95–2.02 Å. There are three inequivalent O sites. In the first O site, O is bonded in a distorted linear geometry to four equivalent Sr and two equivalent Fe atoms. In the second O site, O is bonded to four equivalent Ba and two equivalent Fe atoms to form distorted OBa4Fe2 octahedra that share corners with twenty OBa4Fe2 octahedra, edges with four equivalent OBa4Fe2 octahedra, and faces with eight equivalent OBa2Sr2Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°. In the third O site, O is bonded to two equivalent Ba, two equivalent Sr, and two equivalent Fe atoms to form distorted OBa2Sr2Fe2 octahedra that share corners with eighteen OBa4Fe2 octahedra, edges with four equivalent OBa2Sr2Fe2 octahedra, and faces with six OBa4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 0–61°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(FeO2)4 by Materials Project

BaSr(FeO2)4 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.67–3.15 Å. Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.56–3.03 Å. There are two inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.87–1.92 Å. In the second Fe3+ site, Fe3+ is bonded to four O2- atoms to form corner-sharing FeO4 tetrahedra. There is one shorter (1.90 Å) and three longer (1.91 Å) Fe–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Ba2+, one Sr2+, and two equivalent Fe3+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+, one Sr2+, and two equivalent Fe3+ atoms. In the third O2- site, O2- is bonded in a distorted linear geometry to three equivalent Ba2+ and two equivalent Fe3+ atoms. In the fourth O2- site, O2- is bonded to one Ba2+, one Sr2+, and two equivalent Fe3+ atoms to form distorted corner-sharing OBaSrFe2 tetrahedra. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Ba2+, one Sr2+, and two Fe3+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(SnO3)2 by Materials Project

BaSr(SnO3)2 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with four equivalent BaO12 cuboctahedra, corners with eight equivalent SrO12 cuboctahedra, faces with two equivalent SrO12 cuboctahedra, faces with four equivalent BaO12 cuboctahedra, and faces with eight equivalent SnO6 octahedra. There are four shorter (2.93 Å) and eight longer (2.97 Å) Ba–O bond lengths. Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with four equivalent SrO12 cuboctahedra, corners with eight equivalent BaO12 cuboctahedra, faces with two equivalent BaO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight equivalent SnO6 octahedra. There are eight shorter (2.89 Å) and four longer (2.93 Å) Sr–O bond lengths. Sn4+ is bonded to six O2- atoms to form SnO6 octahedra that share corners with six equivalent SnO6 octahedra, faces with four equivalent BaO12 cuboctahedra, and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–2°. There are a spread of Sn–O bond distances ranging from 2.05–2.10 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to four equivalent Ba2+ and two equivalent Sn4+ atoms to form a mixture of distorted corner and edge-sharing OBa4Sn2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O2- site, O2- is bonded in a distorted linear geometry to four equivalent Sr2+ and two equivalent Sn4+ atoms. In the third O2- site, O2- is bonded in a distorted linear geometry to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Sn4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr by Materials Project

BaSr crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. Ba is bonded in a distorted body-centered cubic geometry to four equivalent Ba and four equivalent Sr atoms. All Ba–Ba bond lengths are 4.27 Å. All Ba–Sr bond lengths are 4.22 Å. Sr is bonded in a distorted body-centered cubic geometry to four equivalent Ba and four equivalent Sr atoms. All Sr–Sr bond lengths are 4.27 Å.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(CuO2)2 by Materials Project

BaSr(CuO2)2 crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. Ba2+ is bonded in a distorted body-centered cubic geometry to eight equivalent O2- atoms. All Ba–O bond lengths are 2.79 Å. Sr2+ is bonded in a body-centered cubic geometry to eight equivalent O2- atoms. All Sr–O bond lengths are 2.63 Å. Cu2+ is bonded in a rectangular see-saw-like geometry to four equivalent O2- atoms. All Cu–O bond lengths are 1.99 Å. O2- is bonded to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Cu2+ atoms to form a mixture of distorted corner, edge, and face-sharing OBa2Sr2Cu2 octahedra. The corner-sharing octahedra tilt angles range from 0–65°.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(CoO3)2 by Materials Project

BaSr(CoO3)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Ba2+ is bonded to twelve O2- atoms to form BaO12 cuboctahedra that share corners with six equivalent BaO12 cuboctahedra, corners with six equivalent CoO6 octahedra, faces with two equivalent BaO12 cuboctahedra, faces with six equivalent SrO12 cuboctahedra, and faces with six equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are six shorter (2.82 Å) and six longer (2.97 Å) Ba–O bond lengths. Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, corners with six equivalent CoO6 octahedra, faces with two equivalent SrO12 cuboctahedra, faces with six equivalent BaO12 cuboctahedra, and faces with six equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 14°. There are six shorter (2.82 Å) and six longer (2.96 Å) Sr–O bond lengths. Co4+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with three equivalent BaO12 cuboctahedra, corners with three equivalent SrO12 cuboctahedra, faces with three equivalent BaO12 cuboctahedra, faces with three equivalent SrO12 cuboctahedra, and faces with two equivalent CoO6 octahedra. All Co–O bond lengths are 1.89 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Co4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, two equivalent Sr2+, and two equivalent Co4+ atoms.

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(FeO2)4 by Materials Project

Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

36 MATERIALS SCIENCE↗

DOE OSTI2020

Materials Data on BaSr(FeO2)4 by Materials Project

36 MATERIALS SCIENCE↗

NASA NTRS2000

In-plane and Interlaminar Shear Strength of a Unidirectional Hi-nicalon Fiber-reinforced Celsian Matrix Composite

In-plane and interlaminar shear strength of a unidirectional SiC fiber-reinforced (BaSr)Al2Si2O8 celsian composite were measured by the double-notch shear test method between room temperature and 1200 C. The interlaminar shear strength was lower than the in-plane shear strength at all temperatures. Stress analysis, using finite element modeling, indicated that shear stress concentration was not responsible for the observed difference in strength. Instead, the difference in layer architecture and thus, the favorable alignment of fiber-rich layers with the shear plane in the interlaminar specimens appears to be the reason for the low strength of this composite. A rapid decrease in strength was observed with temperature due to softening of the glassy phase in the material.

Uenal, O.↗