engleski

The Optimization of Hydrothermal Method for the Synthesis of Triple Perovskites with a Sr3Mn2(W/Te)O9 Structure Type

This study presents an optimization of hydrothermal synthesis of triple perovskites Sr3Mn2WO9 and Sr3Mn2TeO9, from an aqueous solution of metal salt precursors. Usually, a synthesis of perovskite materials demands a controlled and long‐term annealing. In this research, milder conditions (a relatively low temperature, 150 ºC and 200 ºC) and shorter reaction time (24 h) were created, which are environmentally friendly and low-cost. A continuous development contributes to the new and more advanced nanosized materials. It is important for a design of perovskite materials to stabilize the metal cations in certain oxidation states. For that purpose, electrochemical measurements were carried out to determine an oxidation state of manganese cation in the given reaction conditions. The electrochemical results indicate that manganese is in the +3 oxidation state while being transformed into a desired compound. This oxidation state is stabilized by the usage of a strong base (sodium hydroxide). An interesting fact is that Mn3+ (coordination number 6, a high spin state) has an ionic radius of 0.645 Å, which corresponds to the ionic radius of Fe3+ (also coordination number 6, a high spin state). Hence, a structural similarity to Sr3Fe2WO9 and Sr3Fe2TeO9, is expected. In conclusion, the composition, morphology, and stability of prepared compounds were investigated by means of the powder X‐ray diffraction (PXRD), Fourier‐transform infrared spectroscopy (FT-IR), thermogravimetric analysis coupled with the differential scanning calorimetry (TGA/DSC) and the X‐ray photoelectron spectroscopy (XPS). This research is a part of the Croatian Science Foundation project entitled Investigation of Complex Multiferroic Materials Prepared by the Solution Chemistry Methods under the supervision of Prof. Igor Đerđ, Ph.D.

perovskite ; hydrothermal synthesis ; nanomaterials

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