A. Sagara

K. Matsuda

S. Murakami

T. Muroga

T. Shinkawa

T. Tanaka

T. Watanabe

Y. Hishinuma

Y. Tasaki

National Institute for Fusion Science (NIFS-Repository)

Erbium oxide (Er2O3) was shown to be the promising one of the candidate oxide coating materials to prevent magneto-hydrodynamic (MHD) pressure drop because of its high stability in liquid lithium and high electrical resistivity from the results of Er2O3 bulk and Physical Vapor Deposition (PVD) thin film. Furthermore, Er2O3 is also known to be a candidate for the tritium barrier coating. We have been applied Metal Organic Chemical Vapor Deposition (MOCVD) process to form large area oxide coating into duct tubing. We succeeded to make Er2O3coating layer on metal substrate using MOCVD process. We found that the hydrogen permeation quantity was decreased compared with that of stainless steel (SUS 316) substrate without coating and it suggested that Er2O3coating layer was also effectively able to become one of the candidate materials as the hydrogen permeation barrier.  In order to enhance these properties of Er2O3 as the electrical insulator for MHD and hydrogen permeation barrier coating, it is necessary to form thicker and higher crystanity of Er2O3 coating layer. However, the epitaxial growth like the chemical vapor deposition is difficult to form thicker coating layer. We approached and investigated to form the double stacking coating layer on the SUS substrate using intermediate layer (buffer layer) for the thicker and high crystanity of Er2O3 coating formation. Generally, it is well known that the crystanity and alignment of coating layer affected by the lattice constant of the substarate. It is possible to the high crystanity of Er2O3 coating by the buffer layer formation with similar Er2O3 lattice constant between Er2O3 and substarte. The relationship of lattice constant between coating and substrate is often discussed using mismatch factor. The mismatch factor is estimated by the following formula; Mismatch factor  f = |(b-a)| / a a: lattice constant of substrate, b: lattice constant of coating The consistence between coating layer and metal substrate intend to be better with similar to the mismatch factor. In this study, Y2O3 and CeO2 having the similar lattice constant of Er2O3 and SUS materials were selected as the buffer layer. Table.1 indicates the summary of mismatch factor in this study.  Typical image and X-ray diffraction of the Er2O3/CeO2 multilayered coating sample are shown in Fig.1. We found that the interference band was decreased compared with no buffer coating sample. It suggested that coating thickness uniformity was improved by the buffer layer on substrate. From the X-ray diffraction, main diffraction peaks of Er2O3 and CeO2 phases were also observed sharply. We concluded that Er2O3 coating layer was easily formed on CeO2 buffer layer by MOCVD, and buffer layer was effective to form homogeneous coating layer. TEM image of the cross-sectional area in on the Er2O3/CeO2 multilayered ceramic coating on the stainless steel substrate is shown in Fig.2. Er2O3 crystal formed columnar-like structure and it formed densely compared with the sample without CeO2 buffer layer. The origin of grain growth of Er2O3 crystal seemed to be CeO2 crystals. In the future, the microstructure of Er2O3/Y2O3multilayered coating samples will be also investigated. Table.1 The comparisons of lattice mismatch factor between various multilayered coating case SUS316 200 nmDepoEr2O3CeO2Fig.2 TEM image of cross-section area on the Er2O3/CeO2multilayered ceramic coating on the stainless steel (SUS 316) substrate. Fig.1 Typical X-Ray diffraction of the Er2O3/CeO2multilayered ceramic coating on the stainless steel (SUS 316) substrate. 323§4. Synthesis of Er2O3/buffer Multilayered Ceramic Coating for an Advanced Breeding Blanket SystemsHishinuma, Y., Tanaka, T., Watanabe, T., Sagara, A., Muroga, T.,  Shinkawa, T., Murakami, S., Matsuda, K. (Univ. Toyama),  Tanaka, T., Tasaki, Y. (Toshima MFG Co., Ltd.)

Synthesis of Er2O3/buffer Multilayered Ceramic Coating for an Advanced Breeding Blanket Systems

Synthesis of Er2O3/buffer Multilayered Ceramic Coating for an Advanced Breeding Blanket Systems

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