Preparation of Erbium Oxide Tritium Barrier Coating through Metal Organic Decomposition

Er₂O₃ tritium barrier coating was deposited on RAFM steel substrate by using metal-organic decomposition (MOD) method, where the precursor solution was prepared by using low boiling point esters and erbium carboxylates. TG-DSC synchronous thermal analysis was used to analyze the precursor solution, in order to identify film formation temperature. Microstructure of the coating was analyzed by using SEM, EDS and XRD. The decomposition process of the MOD precursor includes solvent evaporation, volatilization and reaction of macromolecular substances and decomposition of metal organic matters. The evaporation and decomposition stage was accompanied by hydrolysis and crystallization process. Mass fraction of the erbium salt has a strong influence on microstructure of the coatings. When the mass fraction of erbium is 2.3 wt.%, the substrate can be entirely covered, forming dense coating with desired tritium resistance factor. When the heat treatment temperature is too high, the coating tends to crack. The optimal heat treatment temperature is 600 ℃. The Er₂O₃ coating prepared in this work has promising electrochemical corrosion resistance, compactness and strong film-substrate adhesion. The Er₂O₃ coating has room temperature resistivity of 3.4 × 10⁹ Ω·cm, which meets the requirements of the preliminary design of the fusion reactor.