Microstructure and deuterium resistance of Al2O3/Y2O3 composite coating with different annealing atmospheres

The Al2O3/Y2O3 composite coating with a total thickness of 320 nm was prepared by radio-frequency magnetron sputtering. The annealing treatments in three different atmosphere, Ar gas, H2 and vacuum, were performed in order to study the influence of microstructure on the deuterium resistance of the coating. The results show that the coating remains dense and the interface is clear after annealing treatment. The Al2O3/Y2O3 coating annealed in Ar gas and H2 atmosphere is composed of c-Al2O3 and cubic Y2O3 phase. However, only cubic Y2O3 phase exists in the coating annealed in vacuum atmosphere. Compared with the 316L stainless steel substructure, the coating sample can reduce deuterium permeability by 2-3 orders of magnitude, showing good deuterium resistance. The oxygen vacancies exist in the coating due to the reduction of H2 in the H2 annealing atmosphere, which provides a fast diffusion channel for the permeation of deuterium; in addition, the larger surface roughness after vacuum annealing increases the adsorption amount of deuterium molecules in surface of coating, which increases the deuterium permeability. After the sample was annealed in Ar atmosphere, the suitable surface morphology makes it have good deuterium barrier performance. The deuterium permeability is the lowest at 700 similar to C and 80 kPa, and the specific value is 9.99477 9 10-14 mol similar to m-1 similar to s-1 similar to Pa-0.5. The research shows that the presence of the coating reduces the deuterium permeability, and the difference in deuterium resistance is mainly affected by the surface roughness and the microdefects in the coating.