According to one embodiment, a structure includes a polycrystalline substance of yttrium oxyfluoride as a main component. The yttrium oxyfluoride has an orthorhombic crystal structure, and an average crystallite size of the polycrystalline substance is less than 100 nanometers. When taking a peak intensity detected near diffraction angle 2θ=32.0° by X-ray diffraction as γ, and taking a peak intensity detected near diffraction angle 2θ=32.8° as δ, a peak intensity ratio γ/δ is not less than 0% and not more than 150%.