Material and Structure Tailored La‐Doped ZrO ₂ Submicrosphere Metacoatings for High‐Performance Space Radiative Cooling

ABSTRACT Advancing space thermal management requires radiative cooling materials with ultralow solar absorptance and exceptional irradiation resistance, yet conventional coatings fall short due to intrinsic UV absorption, suboptimal material, and structural design. Here, bandgap engineering is integrated with photonic structure optimization to develop all‐inorganic metacoatings that overcome these issues. Density functional theory identifies La as ideal dopant for ZrO 2 , as it enlarges the bandgap and enhances lattice stability, suppressing UV absorption and irradiation‐induced defect formation. Monte Carlo simulations determine the optimal submicrosphere diameter (∼0.7 µm) and volume fraction (35%) for maximal solar backscattering. Then we successfully and controllably synthesized the designed La‐doped ZrO 2 submicrospheres and fabricated metacoatings via scalable spray‐coating. The metacoating achieves ultralow solar absorptance ( α s = 0.061) and high thermal emittance ( ε = 0.941) at ∼100 µm, yielding the lowest α s / ε value among the commercial and reported coatings. Under AM0 illumination, it delivers a net cooling power of 280 W·m −2 and reduces temperature by 78°C relative to uncoated Al substrate. The metacoating exhibits excellent irradiation stability with minimal optical degradation after proton, electron, atomic oxygen, and UV exposures, and remains stable after 50 thermal cycles (−196°C to 150°C). This work offers a general strategy for high‐performance radiative cooling materials in extreme space environments.