New hexagonal perovskite with Mn4+ and Mn5+ at distinct structural positions. (September 2015)

• Record Type: Journal Article
• Authors: Tarakina, N V; Tyutyunnik, A P; Bazuev, G V; Vasilev, A D; Berger, I F; Gould, C; Nikolaenko, I V
• Is Part Of: Journal of physics. Number 644(2015)
• Publication Date: 2015-09
• Subjects: Physics -- Congresses; 530.5
• DOI: 10.1088/1742-6596/644/1/012004
• Languages: English
• ISSNs: 1742-6588

Abstract

Abstract: A new hexagonal perovskite, Ba7 Li1.75 Mn3.5 O15.75, has been synthesised using microwave-assisted solid-state synthesis. Its crystal structure has elements typical for the layered hexagonal perovskites and quasi-one-dimensional oxides, hence representing a new polytype. Structural solution based on simultaneous refinement of X-ray and neutron diffraction data shows that Ba7 Li1.75 Mn3.5 O15.75 crystallizes in a hexagonal unit cell with parameters a = 5.66274(2) Å and c = 16.7467(1) Å ( V = 465.063(4) Å 3 ). Columns of face- shared octahedra occupied by Mn 4+, Li + cations and vacancies along the c axis are separated in the ab plane by barium atoms, so that every sixth layer, the coordination of Mn 5+ and Li + changes to tetrahedral. Separation of Mn 4+ and Mn 5+ cations in two distinct structural positions makes the structure unique. A scanning transmission electron microscopy study revealed the formation of a rhombohedrally centered supercell, which might be attributed to the ordering of manganese and lithium atoms among cationic sites.