Fabrication of yttrium oxide and erbium oxide coatings by PVD methods

The development of insulating coatings is one of the most important subjects in fusion reactor liquid lithium blanket research and development. The compounds aluminum nitride, yttrium oxide and erbium oxide are considered to be candidate materials for ceramic coatings because of their high electrical resistance and their high compatibility with liquid lithium. In the present study, two types of PVD methods were employed for fabrication of coatings, and their properties were examined. Yttrium oxide and erbium oxide coatings were fabricated by means of radio frequency (RF) sputtering, and erbium oxide coatings were fabricated by arc source plasma assisted deposition. The coatings were all close to their stoichimetric composition, and had higher resistances than that required in the fusion reactor (102–104 Ωm). The coatings had the crystallinity observed by X-ray diffraction (XRD), which were influenced by fabrication parameters as high frequency electric power or substrate temperature. Annealing after fabrication makes coatings crystallized more while the crystallinity of the coatings fabricated at low temperature were inferior to that of the coatings fabricated at higher temperature.