Ba₄Ta₂O₉ Oxide Prepared from an Oxalate-Based Molecular Precursor—Characterization and Properties

Abstract

A novel heterometallic oxalate-based compound, {Ba 2 (H 2 O) 5 [TaO(C 2 O 4 ) 3 ]HC 2 O 4 }•H 2 O (1), was obtained by using an (oxalato)tantalate(V) aqueous solution as a source of the complex anion and characterized by X-ray single-crystal diffraction, IR spectroscopy, and thermal analysis. Compound 1 is a three-dimensional (3D) coordination polymer with the Ta atom connected to eight neighboring Ba atoms through the oxalate ligands and the oxo oxygen group. Thermal treatment of 1 up to 1200 °C leads to molecular precursor-to-material conversion that yields the mixed-metal γ-Ba 4 Ta 2 O 9 phase. This hightemperature γ-Ba 4 Ta 2 O 9 polymorph has the 6H-perovskite structure (space group P6 3 /m), in which the Ta 2 O 9 face-sharing octahedral dimers are interconnected via corners to the regular BaO 6 octahedra. To date, γ-Ba 4 Ta 2 O 9 has never been obtained at room temperature, because of the reduction of symmetry (P6 3 /m → P2 1 /c) that usually occurs during the cooling. Spectroscopic, optical, photocatalytic, and electrical properties of the obtained γ-Ba 4 Ta 2 O 9 phase were investigated. In addition to the experimental data, an absorption spectrum and band structure of the γ-Ba 4 Ta 2 O 9 polymorph were calculated using density functional theory.

1D Heterometallic Oxalate Compounds as Precursors for Mixed Ca–Cr Oxides – Synthesis, Structures, and Magnetic Studies

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“…[15] Heterometallic oxalate complexes have already been used for the preparation of mixed-metal oxides. [15][16][17][18][19][20][21][22][23] In our recently published articles, we reported the use of the new compound {Ba 2 O 9 through thermal decomposition at a specific temperature. [21,22] The molecular-to-materials conversion of the isostructural Ba II …”

Crystal disassembly and reassembly of heterometallic NiII–TaVoxalate compounds

“…13 Following a simple procedure, similar to the one we used for the preparation of the 13 21 From this it is evident that bulky cations, such as ijNiIJphen) 3 ] 2+ and ijNiIJbpy) 3 ] 2+ , dictate the structural arrangement and also influence changes in the coordination sphere of tantalum. The tendency of Ni II -Ta V oxalate systems with bpy ligands to crystallize with more water molecules is probably due to the existence of more voids in the structures (in relation to similar compounds with phen ligands).…”

Single‐step preparation of rutile‐type CrNbO4 and CrTaO4 oxides from oxalate precursors–characterization and properties

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