High-entropy mixed-valence perovskites enabling concurrent suppression of radiative and conductive heat transfer

Thermal camouflage at high temperatures requires simultaneous suppression of infrared radiation and heat conduction, which conflict in most materials. Conventional ion doping reduces infrared emissivity but often increases thermal conductivity, whereas low thermal conductivity ceramics exhibit high emissivity from strong phonon-polariton vibrations. Here, we designed and synthesized a high-entropy cobalt-based perovskite by engineering the A‑site chemistry of SmCoO₃ via aliovalent substitution and mixed‑valence cobalt chemistry using a solid‑state reaction at 1200 ℃. Its properties are characterized, and its electronic band structure is investigated by first‑principles calculations. Aliovalent substitution induces stable oxygen vacancies and Co³⁺/Co⁴⁺ double-exchange interactions, producing an electronic response that strongly suppresses mid- to far-infrared radiation. This yields an ultra-low broadband (2.5–20 μm) emissivity of ∼0.25 from 25 ℃ to 1000 ℃. Entropy‑driven lattice disorder enhances phonon scattering, resulting in a low phonon thermal conductivity of 1.99 W·m⁻¹·K⁻¹. These results enable concurrent suppression of radiative and conductive heat transfer for high-temperature thermal camouflage.