Disclosed are a material for spray for plasma spray coating having high plasma resistance and a method for producing the same. The material for plasma spray comprises an yttrium compound, and the numbers of moles of Y (yttrium), O (oxygen), and F (fluorine) in the yttrium compound satisfy 1.5<(O+F)/Y<2.0.

A method for producing a ceramic scintillator comprising the steps of mixing a rare earth compound with sulfuric acid and/or sulfate to cause their reaction to obtain a product; calcining the product to obtain calcined powder; reducing the calcined powder to obtain rare earth oxysulfide powder; molding the rare earth oxysulfide powder to obtain a green body; and sintering the green body; a pulverization step being conducted to adjust the particle sizes of the product and/or the calcined powder at least before the reduction step.

A structure includes a polycrystalline substance of yttrium fluoride, wherein an average crystallite size in the polycrystalline substance is less than 100 nanometers. When taking a peak intensity detected near diffraction angle 2=24.3 by X-ray diffraction as , and taking a peak intensity detected near diffraction angle 2=25.7 as , a peak intensity ratio / of the structure is not less than 0% and less than 100%.

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 2=13.8 by X-ray diffraction as r1, taking a peak intensity of rhombohedron detected near diffraction angle 2=36.1 as r2, and taking a proportion 1 as 1(%)=r2/r1100, the proportion 1 is not less than 0% and less than 100%.

A sprayed article is prepared by thermally spraying ceramic particles of rare earth oxide or fluoride or metal particles of W, Mo or Ta onto an outer or inner surface of a cylindrical carbon substrate to form a sprayed coating, and burning out the carbon substrate, thus leaving the ceramic or metal-base sprayed coating of cylindrical shape having a wall thickness of 0.5-5 mm.

A sprayed article is prepared by thermally spraying ceramic particles of rare earth oxide or fluoride or metal particles of W, Mo or Ta onto an outer or inner surface of a cylindrical carbon substrate to form a sprayed coating, and burning out the carbon substrate, thus leaving the ceramic or metal-base sprayed coating of cylindrical shape having a wall thickness of 0.5-5 mm.

This invention provides a thermal spray material capable of forming a thermal spray coating excellent in plasma erosion resistance as well as in properties such as porosity and hardness. The thermal spray material comprises a rare earth element oxyhalide (RE-OX) which comprises a rare earth element (RE), oxygen (O) and a halogen atom (X) as its elemental constituents. The thermal spray material has an X-ray diffraction pattern that shows a main peak intensity I.sub.A corresponding to the rare earth element oxyhalide, a main peak intensity I.sub.B corresponding to a rare earth element oxide and a main peak intensity I.sub.C corresponding to a rare earth element halide, satisfying a relationship [(I.sub.B+I.sub.C)/I.sub.A]<0.02.

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 2=32.0 by X-ray diffraction as , and taking a peak intensity detected near diffraction angle 2=32.8 as , a peak intensity ratio / is not less than 0% and not more than 150%.

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 2=13.8 by X-ray diffraction as r1, taking a peak intensity of rhombohedron detected near diffraction angle 2=36.1 as r2, and taking a proportion 1 as 1(%)=r2/r1100, the proportion 1 is not less than 0% and less than 100%.

Described are coatings that contain of fluorinated yttrium oxide and a metal oxide; methods of preparing these coatings; substrates, surfaces, equipment, and components of equipment that include a coating that contains a combination of fluorinated yttrium oxide and a metal oxide; and methods of preparing and using the coatings and coated substrates.