Preparation of Al2O3/Y2O3 composite coating for deuterium permeation reduction

A tritium permeation barrier is required in fusion blankets for the reduction of fuel loss and radiological hazard. In this study, an Al2O3/Y2O3 composite coating was prepared on 316L stainless steel by radiofrequency magnetron sputtering in order to improve the tritium permeation resistance. The microstructure and the phase composition of the Al2O3/Y2O3 composite coating are observed by scanning electron microscopy, transmission electron microscopy and grazing incidence X-ray diffraction. Moreover, Auger electron spectroscopy was used to characterize the depth profiles of Al, Y and O elements. The results clearly indicate that the Al2O3/Y2O3 composite coating is fully dense and the total thickness is approximately 340 nm. The Al2O3/Y2O3 coating consists of an amorphous Al2O3 and the cubic Y2O3, in which Al, Y and O elements are homogeneously distributed in the vertical base direction. Furthermore, the deuterium permeation property of the Al2O3/Y2O3 composite coating was measured by the gas phase permeation method. The results show that the introduction of an interface and the existence of a tiny amount of micro-defects improve the deuterium resistance of the Al2O3/Y2O3 coating, and its deuterium permeation reduction factor is 536-750 at 873-973 K. Therefore, it is concluded that the Al2O3/Y2O3 composite coating as deuterium permeation barrier can significantly enhance the deuterium permeation resistance property. (C) 2020 Published by Elsevier B.V. on behalf of Chinese Society of Rare Earths.