Compositionally complex spinel-type oxides for advanced applications

High-entropy spinel oxides (HESOs) represent a class of complex oxides, comprising of five or more metal cations distributed within a spinel crystal structure. Their structural complexity and tunable physical properties make them promising candidates for various advanced applications. Although multiple synthesis approaches have been explored to date, the development of novel, efficacious synthesis routes continues. In this study, HESOs with eight distinct compositions were synthesized utilizing the self-propagating room temperature method. Following thermal treatment at 1000 °C, XRD confirmed the formation of single-phase spinel (Fd-3m) oxides. Spark plasma sintering was successfully employed for the first time to densify HESOs, leading to relative densities between 94% and 99% while preserving the spinel phase. With a holding time of only 10 minutes, process efficiency was notably enhanced. SEM/EDS revealed a dense and homogeneous microstructure with minimal porosity. The obtained materials exhibit characteristics suitable for a broad spectrum of applications, including thermal barrier coatings, microwave absorbers, solid oxide fuel cell (SOFC) cathodes, and gas sensors. This study presents a straightforward and effective route for the synthesis and densification of HESOs, contributing to the understanding of their properties.