engleski

Molecular precursor-to-material approach for complex perovskite-type oxides

The perovskite family of oxides is very attractive area of research in material science community because of the diversity of their physical and chemical characteristics, which offers opportunity to explore new functionalities and potential applications, such as photocatalysis, light harvesting, superconductivity, magnetoresistance, ferroelectric, multiferroic or dielectric performance. In general complex perovskite oxides with A2B'B''O6 or A3B'B''B'''O9 formula, where A are alkali, alkaline earth or rare earth elements, while the B', B'' and B''' cations can be any transition element, have crystal structure that consists of the corner sharing B'O6, B''O6 and B'''O6 octahedra, and A atoms located in the space between the octahedra. A variety of devices and methods have previously been used to prepare and characterize perovskite compounds, however most common method of their preparation is solid state reaction at high temperatures. Herein we propose novel pathway for the synthesis of perovskite-type oxides through molecular precursor-to-material approach, which uses heterometallic complexes as precursors for oxides. Thermal decomposition of the mixture of the well-defined and structurally characterized heterometallic oxalate-based compounds {; ; ; Ba2(H2O)5[NbO(C2O4)3]HC2O4}; ; ; ·H2O and [Ni(bpy)3]2[TaO(C2O4)3]Cl·12H2O leads to highly crystalline Ba3(NiNbTa)O9 oxide. We have also shown that Ba2NbCrO6 perovskite-type oxide can be obtained in thermal treatment of {; ; ; Ba2(H2O)5[NbO(C2O4)3]HC2O4}; ; ; ·H2O and (NH4)3[Cr(C2O4)3]·3H2O. The phase formation and structural ordering of oxides obtained by modified molecular precursor- to-material method has been investigated through a combination of thermal analysis (TGA and DTA), powder X-ray diffraction, scanning electron microscopy and energy-dispersive X-ray spectroscopy. We have shown that ratio of metals can be finely tuned with the careful choice of molecular precursors as well as by appropriate amount of initial heterometallic complexes taken for the thermal decomposition reaction. The preparation strategy described here could be extended for the synthesis of various other complex perovskites at relatively mild conditions.

Perovskite-type oxides ; Crystal structure ; Powder X-ray diffraction

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