High-entropy aluminate spinel oxides: A pathway to advanced functional materials

This study investigates the synthesis and characterization of high-entropy aluminate spinel oxides (Al-HESOs) with three distinct compositions: (Co,Mn,Ni,Zn,Cu)Al₂O₄, (Co,Mn,Ni,Zn)Al₂O₄, and (Co,Mn,Ni,Mg)Al₂O₄. Using the self-propagating room temperature method for synthesis and spark plasma sintering for densification, single-phased Al-HESOs with relative densities up to 97 % were successfully obtained. Structural, mechanical, and thermal properties were comprehensively analysed, demonstrating significant tunability. Notably, the inclusion of Cu²⁺ drastically reduced the Young's modulus (3.8 GPa) while maintaining high hardness (9.9 GPa) and low thermal diffusivity (0.78 mm² s⁻¹ at room temperature – 0.63 mm² s⁻¹ at 600 °C), positioning (Co,Mn,Ni,Zn,Cu)Al₂O₄ as a promising candidate for strain-compliant thermal barrier coatings. These findings establish a novel synthesis and densification route for Al-HESOs and their potential for applications in advanced energy, sensing, and thermal management technologies.