High-entropy spinel oxides: fundamentals, synthesis and characterization

Abstract

High-entropy spinel oxides (HESOs) are oxides with 5 or more cations with the general formula AB2O4 and the spinel ( Fd 3m ) structure. Due to their unique structure and properties, HESOs have shown great potential in various technological applications, i.e. they can be used as catalysts, adsorbents and photocatalysts. Since the first successful synthesis in 2018, researchers have been experimenting with different precursors and synthesis methods. However, further research is still needed in order to fully understand their capabilities and exploit their properties. The aim of this research is to synthesize novel HESOs using the self-propagating room temperature (SPRT) method, which is time and cost-effective and has not been utilized so far. Our results indicate that chlorides are not good precursors, since the formation of spinel structure has not been achieved. On the other hand, the use of nitrates has successfully led to a primary spinel ( Fd 3m ) phase. Still, certain issues persist, as secondary phases are commonly formed, especially in the presence of Mg or Cu. A potential solution that could ensure the formation of a single phase is the use of quenching from high temperatures (1000 °C), instead of gradual cooling

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