Compositional tuning of structural, photothermal and optical properties of La-based high-entropy perovskite oxides

In this study, 14 lanthanum-based high-entropy perovskite oxides (HEPOs) with equimolar mixtures of transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) at the B-site were synthesized to investigate how multi-elemental interactions govern their structural and optical properties. Most compositions form single-phase perovskites after annealing at 1200 °C, as confirmed by XRD and Rietveld refinement. SEM and EDS reveal homogeneous elemental distributions with particle sizes tunable from < 250 nm to > 2 µm depending on composition. UV–Vis-NIR spectrometry shows broad absorption without a distinct measurable onset, while the electronic structure remains robust across the series. Ionisation potentials shift by up to 0.55 eV with cationic composition, demonstrating systematic compositional tuning of the occupied band (analogous to the valence band maximum). Photoluminescence measurements indicate thermally driven emission resembling broadband thermal radiation, consistent with a strong photothermal response in these materials. These results highlight high-entropy perovskite oxides as a versatile platform for engineering structural disorder, electronic energy-level alignment, and photothermal behavior, opening pathways toward oxide-based broadband infrared emission and high-temperature photothermal applications.