Preparation of yttrium oxide coating by MOCVD as tritium permeation barrier

• Yttrium oxide coating was deposited on 316L substrate as hydrogen permeation barrier.
• O:Y ratio of the 700 °C annealed coating corresponds well to the stoichiometric Y2O3.
• The original precursor completely decomposed within the coating annealed at 700 °C.
• The 700 °C annealed coating offers efficient inhibition to deuterium permeation.
• Deuterium permeation of the 700 °C annealed coating is controlled by a hybrid regime.

Yttrium oxide coatings were deposited on 316L substrate using metal organic chemical vapor deposition (MOCVD) technique with yttrium β-diketonates organometallic Y(tmhd)3 as precursor. The different microstructures were obtained by annealing coatings at 700 °C or as-deposited. The film was characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), infrared spectroscopy and X-ray photoelectron spectroscopy (XPS). The hydrogen permeation inhibition performance of films was investigated by deuterium permeation experiment. The crystalline structure of the coatings depended on the post-anneal; the crystallite size of the coating increases and the surface exhibits compact surface morphology for the coatings post-annealed at 700 °C. The coating post-annealed at 700 °C has the correct oxygen/yttrium ratio corresponding well to the stoichiometric Y2O3, while some concentrations of carbon and hydrogen impurities were found in the as-deposited coating. The impurities are present in the form of unreacted or partially reacted precursor molecules due to the incomplete decomposition of the original precursor. The deuterium permeability of the coating improved obviously after post-anneal and was around 240–410 times less than that of the 316L stainless steel, which means efficient inhibition to deuterium permeation.