Enhanced solar reflectance of sputtered yttrium-stabilized zirconia-coated aluminum for solar thermal systems

Aluminum (Al)-based solar reflectors (SR) play a crucial role by reflecting sunlight across a broad wavelength range in high-temperature solar thermal systems, significantly impacting overall system performance for optimal energy generation and industrial processes. However, the optical performance and longevity of the SR are often limited by environmental degradation under extreme operating conditions. To address these challenges, we deposited yttrium-stabilized zirconia (YSZ) thin films on Al substrates via radio-frequency (RF) magnetron sputtering. The crystallized YSZ thin films with a columnar structure exhibited a dense, smooth, and crack-free surface morphology, characterized by a low roughness of 1.78 nm, which effectively enhanced solar reflectance (R) and adhesion strength. Specifically, the films achieved a peak R of 99.91 % in the wavelength range of 300–2500 nm, with a solar-weighted reflectance (SWR) of 94.82 % under the AM 1.5G spectrum. Additionally, a high R of 99.43 % was maintained in the 2.5–15 μm range. Meanwhile, with the increase in the thickness of the YSZ films, the nano-mechanical adhesion strength can be enhanced from 4.7 mN to 18 mN. Our findings demonstrate that sputtered YSZ films show potential for optimizing the optical performance and durability of Al-based SR, making them a promising candidate for advanced solar thermal applications.