| abstract |
According to one embodiment, a structure includes a polycrystalline substance of yttrium oxyfluoride as a main component. The yttrium oxyfluoride has a rhombohedral crystal structure, and an average crystallite size of the polycrystalline substance is less than 100 nanometers. When taking a peak intensity of rhombohedron detected near diffraction angle 2θ=13.8° by X-ray diffraction as r1, taking a peak intensity of rhombohedron detected near diffraction angle 2θ=36.1° as r2, and taking a proportion γ1 as γ1(%)=r2/r1×100, the proportion γ1 is not less than 0% and less than 100%. |