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Besmann, Theodore

Publications and source records attributed to Besmann, Theodore.

7 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

DFT-guided flux synthesis of a family of layered titanates crystallizing in the lepidocrocite structure type

K 0.72 Fe 0.72 Ti 1.28 O 4 , a layered mixed-metal oxide belonging to the lepidocrocite structure type, was grown out of a molten KCl-KF mixture at 800 °C. The compound crystallizes in orthorhombic space group Cmcm and exhibits two-dimensional layers, composed of mixed Fe/Ti octahedra, separated by K ions that occupy the interlayer layer space and maintain charge balance. The targeted flux synthesis of the Ni, Cu, and Zn analogs was carried out after density functional theory (DFT) calculations predicted their formation to be energetically favorable, yielding K 0.77 Ni 0.38 Ti 1.62 O 4 , K 0.77 Cu 0.38 Ti 1.62 O 4 , and K 0.73 Zn 0.36 Ti 1.64 O 4 . Finally, all four compositions can be prepared via conventional solid-state technique by mixing and heating stoichiometric amounts of KNO 3 , appropriate transition metal oxide precursors, and TiO 2 .

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DOE OSTI2020

Salt-flux synthesis, crystal structure and theoretical characterization of Rb 0.74 Ga 6.62 Ti 0·38 O 11

Here single crystals of Rb 0.74 Ga 6.62 Ti 0·38 O 11 (RGTO) were grown from a mixed RbCl–RbF flux at 850 °C. The compound crystallizes in the RbGa 7 O 11 structure type, which is reminiscent of the hollandite and β-Ga 2 O 3 structure types. RGTO crystallizes in the monoclinic space group P2/m with lattice parameters a = 8.3355 (8) Å, b = 3.0286 (3) Å, c = 9.5028 (9) Å, and β = 114.620 (3)°. The crystal structure of RGTO is comprised of GaO 6 and mixed (Ga/Ti)O 6 octahedra and GaO 4 tetrahedra connected in a complex three-dimensional, anionic framework exhibiting eight-sided channels that are occupied by disordered Rb cations required for charge balance. First-principles calculations in the form of density functional theory were performed, which indicated the complex to be a charge transfer semiconductor.

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