Modified precursor route to the multimetallic oxides using oxalate complexes Marijana Jurić , Martina Vrankić, Jasminka Popović, Lidija Androš Dubraja Ruđer Bošković Institute, Bijenička cesta 54, Zagreb, Croatia The properties of the mixed metal oxides, an important class of advanced materials, could be greatly influenced by crystallinity, particle size, phase present, and morphology. These can be tuned, in part, by changing and modifying the synthesis methods. The use of heterometallic complexes as single source precursors provides a simplified synthetic route through one-step thermal decomposition to form the mixed metal oxides. The advantage of a solid phase transition is the retention of the elemental composition defined by the molecular precursor with only a loss of volatile decomposition products – allowing excellent stoichiometric control of the intermetallic ratio in the oxide products. It is well known that the release of organic gases affects the particle size and porosity of the produced oxide; as the organic content in the starting materials is increased, the larger porosity and smaller particle sizes in the decomposition products are more pronounced. In addition, the effects of the temperature level and heating rate strongly correlate with thermal decomposition and prevention of melting/vaporization of molecular species that may occur due to rapid heating [1] . Since the oxalate group, C 2 O 4 2– , easily decomposes into gaseous at low temperatures, the heterometallic oxalate‐based solids can serve as suitable precursors for the preparation of mixed metal oxides [2] . Heterometallic compounds do not always contain the appropriate ratio of metal ions for the formation of the desired single phase mixed metal oxide. Therefore, we investigated whether the multimetallic oxides containing two or more metals could be prepared by mixing two or more different oxalate precursors in different ratios prior to thermal decomposition [3]. Most perovskite compounds of greatest technological interest are not simple systems but A(B'B'')O 3 , with two different B atoms. Highly crystalline materials Ba(Ni 1/3−x Co x Nb 2/3 )O 3 (x = 0, 1/6 and 1/3] were obtained from pyrolysis of the mixture of the well-defined and structurally characterized heterometallic oxalate-based compounds. Mixing oxalate precursors in various ratios before thermal treatment also allowed the preparation of oxide materials Ni 1−x Co x Nb 2 O 6 , (x = 0, 1/2 and 1). The phase formation and structural arrangement of these multimetallic oxides obtained by this modified precursor route were characterized by powder X-ray diffraction (PXRD) and scanning electron microscopy (SEM). Acknowledgement: This work has been funded by the Croatian Science Foundation under project number IP-2019-04-5742. References 1. H. Lu, D. S. Wright and S. D. Pike, The use of mixed-metal single source precursors for the synthesis of complex metal oxides. Chem. Commun. 2020 , 56, 854-871. 2. L. Molčanov, L. Androš Dubraja, M. Vrankić, M. Jurić, A 3D oxalate-bridged [Cu II Fe II ] coordination polymer as molecular precursor for CuFe 2 O 4 spinel – photocatalytic features. J. Am. Ceram. Soc . 2023, 106 , 2997-3008. 3. J. H. Thurston, T. O. Ely, D. Trahan, K. H. Whitmire, Nanostructured Bimetallic Oxide Ion-Conducting Ceramics from Single- Source Molecular Precursors. Chem. Mater. 2003 , 15 , 4407-4416.
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