Deuterium permeation behavior and its iron-ion irradiation effect in yttrium oxide coating deposited by magnetron sputtering Takumi Chikada a, * , Hikari Fujita a , Jan Engels b , Anne Houben b , Jumpei Mochizuki a , Seira Horikoshi a , Moeki Matsunaga a , Masayuki Tokitani c , Yoshimitsu Hishinuma c , Sosuke Kondo d , Kiyohiro Yabuuchi d , Thomas Schwarz-Selinger e , Takayuki Terai f , Yasuhisa Oya a a Shizuoka University, 836 Ohya, Suruga-ku, 422-8529, Shizuoka, Japan b Forschungszentrum Jülich GmbH, Partner of the Trilateral Euregio Cluster (TEC), 52428, Jülich, Germany c National Institute for Fusion Science, 322-6 Oroshi, Toki, 509-5292, Gifu, Japan d Kyoto University, Gokasho, 611-0011, Uji, Kyoto, Japan e Max-Planck-Institut für Plasmaphysik, Boltzmannstraße 2, 85748, Garching, Germany f The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku,113-8656, Tokyo, Japan highlights  Y 2 O 3 coatings were irradiated using 1.42 MeV Fe þ at different temperatures.  Amorphous layers formed at the coating-substrate interfaces in irradiated coatings.  Voids in the coatings remained and aggregated after deuterium permeation.  Irradiated coatings showed lower deuterium permeation flux than unirradiated.  Irradiation damage would accelerate nucleation of Y 2 O 3 crystal. article info Article history: Received 14 December 2017 Received in revised form 9 May 2018 Accepted 7 June 2018 Available online xxx Keywords: Tritium Permeation Coating Irradiation Yttrium oxide abstract Tritium permeation through structural materials is a critical issue in fusion reactors from the viewpoints of sufficient fuel balance and radiological hazard. Ceramic coatings have been investigated as tritium permeation barrier for several decades; however, irradiation effects of the coatings on permeation are not elucidated. In this work, yttrium oxide coatings were fabricated on reduced activation ferritic/ martensitic steels by radio frequency magnetron sputtering, and their microstructures and deuterium permeation behaviors were investigated before and after iron-ion irradiation at different temperatures. An as-deposited coating had a columnar structure and transformed into a granular one after annealing. An amorphous layer formed near the coating-substrate interface of irradiated coatings, and its thickness became thinner with increasing irradiation temperature. Voids of approximately 20 nm in diameter also formed in the irradiated coatings. Deuterium permeation flux of the sample irradiated to 1 dpa at room temperature was the lowest among the unirradiated and irradiated samples, and a permeation reduction factor indicated up to 390. The amorphous layer disappeared after deuterium permeation measurements due to damage recovery, while the voids remained and aggregated. The irradiation damage would accelerate nucleation of the crystal, resulting in a decrease of the permeation flux. © 2018 Elsevier B.V. All rights reserved. 1. Introduction Tritium control is a key technical challenge for fusion reactors including ITER, demonstration and commercial reactors. Tritium permeation to cooling channels or outside of the reactor should be mitigated in order to establish an efficient fuel breeding/recovery * Corresponding author. College of Science Shizuoka University, 836 Ohya Suruga-ku Shizuoka, Shizuoka, 422-8529, Japan. E-mail address: chikada.takumi@shizuoka.ac.jp (T. Chikada). Contents lists available at ScienceDirect Journal of Nuclear Materials journal homepage: www.elsevier.com/locate/jnucmat https://doi.org/10.1016/j.jnucmat.2018.06.008 0022-3115/© 2018 Elsevier B.V. All rights reserved. Journal of Nuclear Materials xxx (2018) 1e7 Please cite this article in press as: T. Chikada, et al., Deuterium permeation behavior and its iron-ion irradiation effect in yttrium oxide coating deposited by magnetron sputtering, Journal of Nuclear Materials (2018), https://doi.org/10.1016/j.jnucmat.2018.06.008