Exploring the impact of magnesium on the electronic properties of chromium–aluminium oxides (Al <i>x</i> Cr1− <i>x</i> )2O3 for high-temperature thermal energy storage applications

Abstract

This study investigates the influence of magnesium (Mg) incorporation on the electronic properties of the (AlxCr1−x)2O3 system, a promising conductive material for high-temperature electrified thermal energy storage. An integrated computational and experimental approach with cluster expansion methods and hybrid density functional theory calculations identified the most stable Mg-doped configurations and examined modifications in the electronic structure in mixed Al–Cr oxide environments over a temperature range of 0–2500 K. With Mg inserted into the structures at each composition through comprehensive defect analysis, we determined the intrinsic and extrinsic electronic properties of the (AlxCr1−x)2O3 system across the entire composition range. Experimental validation involved sintering at 1773 K under tailored temperature profiles, followed by extensive electronic characterization. The results reveal that Mg reduces the bandgap through the creation of defect states near the band edges, significantly enhancing the conductivity of the composite. This demonstrates that Mg incorporation alters the electronic properties and improves the electrical conductivity of the material, addressing conductivity limitations in the pristine (AlxCr1−x)2O3 composite and positioning the Mg-modified system as a strong candidate for high-temperature thermal energy storage.