Phosphor powder, light-emitting device, image display device, and illumination device

A phosphor powder which is represented by a general formula Mx(Si, Al)2(N, O)3±y (where M is Li and one or more alkaline earth metal elements and 0.52≤x≤0.9 and 0.06≤y≤0.36 are satisfied) and in which a part of M is substituted with a Ce element,

• wherein the phosphor powder includes phosphor particles in which a Si/Al atomic ratio is equal to or more than 1.5 and equal to or less than 6,
• an O/N atomic ratio is equal to or more than 0 and equal to or less than 0.1,
• 5 to 50 mol % of M is Li, and
• 0.5 to 10 mol % of M is Ce, and
• in a case where a volume-based cumulative 10% particle size, a volume-based cumulative 50% particle size, and a volume-based cumulative 90% particle size of the phosphor powder measured by a laser diffraction scattering method are defined as D10, D50, and D90, respectively, (D90−D10)/D50 is equal to or more than 0.7 and equal to or less than 1.1.