MgGa2O4-based thermal control coating: An ultra-low solar absorption coating with high irradiation stability

In this study, the viability of MgGa2O4 as a pigment for thermal control coatings is discussed. Notably, the MgGa2O4 based coating exhibited excellent initial optical properties and irradiation stability. After irradiation with 40 keV proton at a dose of 1.4 x 1014 P/cm2, the optical performance of the coating remained essentially unchanged, while the solar absorption of the coating is still maintained below 0.10 after irradiation with 40 keV electron at a dose of 1.6 x 1016 e/cm2. Further, the mechanism of the optical changes induced by electron irradiation was elucidated through experimental and computational methods. In MgGa2O4 lattice, two different types of oxygen vacancies and a transition process of them were found. This process was accompanied by the leakage of some oxygen atoms from the lattice, leading to an increased number of color centers and the change in optical properties. Despite the solar absorption raised after electron irradiation, the MgGa2O4 based thermal control coating showed minimal change and low end-of-irradiation-life values, which suggests that they have excellent stability and promising applications.