Preparation and Microstructure of Er₂O₃ Tritium Permeation Barrier

The permeation of hydrogen and its isotopes to steel or other structural materials is undesirable in many technological applications, which could embrittle and shorten their lifetime. The development of the International Thermonuclear Experimental Reactor （ITER） requires a material which is capable of acting as a hydrogen/tritium permeation barrier on a low activation steel. Currentlyα-Al₂O₃ is widely studed because of its high permeation reduction factor （PRF）, good thermal property, and so on. However, the formation ofα-alumina phase is very difficult and it needs very high temperature. Er₂O₃ as a new hydrogen isotope barrier material was wildly reported. It is found that a 1μm thick crystalline erbia coating on a fusion relevant material, could reduce permeability by a factor up to almost 10³. Furthermore erbia has good thermo-mechanical stability on different substrates. Therefore it is proposed as an important candidate for the permeation barrier coating to hydrogen isotope in fusion reactor.In this paper, research advances of the permeation barrier coating to hydrogen isotope have been reviewed. Starting from the precursor of Er（NO₃）₃·5H₂O and collodion, single phase Er₂O₃ coating with dense and homogeneous microstructure, was successfully prepared by sol-gel method. Effect of substrate and processing parameters, such as the collodion concentration, calcination temperature, holding time and cooling ways on the formation and microstructure of Er₂O₃ has been studied detailedly. The processing parameters were optimized and Er₂O₃ coatings, has homogeneous microstructure and good thermal shock resistance, was prepared with good reproductivity.