Phosphor, deep ultraviolet light-emitting device and phosphor production method

The invention provides a phosphor, a deep ultraviolet light-emitting device and a phosphor production method. The phosphor includes particles of halogen-containing magnesium oxide, and emits DUV light, the particles satisfying 0.16 DEG <=FWHM (420)<=0.20 DEG, wherein FWHM (420) is the full width at half maximum of a (420) diffraction peak present at a diffraction angle 2[theta] equal to or more than 109.0 DEG and equal to or less than 110.0 DEG as measured by powder X-ray diffractometry using CuK[alpha] radiation.