Formation of double oxide insulator coating for an advanced breeding blanket

Erbium oxide (Er₂O₃) coating layer is one of the suitable coatings to realize an advanced breeding blanket system because it has high electrical resistivity and hydrogen permeation suppression effect. In order to enhance these properties of Er₂O₃ coating, it is necessary to form a thick coating layer with high crystallinity. The formation of a double stacked coating layer on an austenitic stainless steel 316 substrate using an intermediate layer (buffer layer) was investigated for the thicker and high crystallinity of Er₂O₃ coating formation. Yttrium oxide (Y₂O₃) and cerium oxide (CeO₂) were selected as buffer layer between the Er₂O₃ layer and austenitic stainless steel 316 substrate due to their similar lattice constant to that of Er₂O₃ crystal. The texture and grain growth direction of Er₂O₃ was controlled by the Y ₂O₃ and CeO₂ buffer layer. However, the suppression effect of hydrogen permeation by the double stacked coating was smaller than that of the single layer coating due to the thin Er ₂O₃ formation.