Thermally robust ceria-based coating achieves ultralow mid-infrared emissivity for high-temperature infrared stealth

Effective high‑temperature (> 400 °C) infrared (IR) stealth necessitates dual‑band radiative control: low emissivity in the mid‑wave IR (MWIR, 3–5 μm) atmospheric window to suppress detectability, and high emissivity in the long‑wave IR (LWIR, 8–20 μm) to enable efficient heat dissipation. Herein, a CeO₂/Aluminum Polyphosphate Composite coating (CAPC) with a brick‑and‑mortar architecture is developed via scalable spray application and gradient sintering. CeO₂ particles are annealed at high temperature to enhance crystallinity and increase oxygen vacancy concentration, serving as rigid functional fillers. The in‑situ‑formed aluminum polyphosphate matrix is relatively flexible, providing strong adhesion and stress buffering between the rigid fillers. Benefiting from this brick‑and‑mortar design, the coating delivers coordinated dual‑band modulation, exhibiting an MWIR average emissivity below 0.3 and an LWIR average emissivity above 0.7 over 25–800 °C. Consequently, the high‑temperature radiative of substrate output in the MWIR band is reduced by 51%, while effective LWIR radiative cooling is maintained. This behavior yields pronounced temperature camouflage effects. At 500 °C, the apparent surface temperature is lowered by approximately 84°C relative to an uncoated substrate. The coating also demonstrates excellent thermal stability, withstanding 20 rapid thermal cycles between 800 °C and room temperature and retaining integrity after 10 h of exposure at 800 °C without any noticeable performance degradation. This work offers a viable design strategy and a robust material solution for high‑temperature IR stealth applications.