Blue phosphor, light-emitting device, and plasma display panel

A blue phosphor represented by the general formula xSrO.yEuO.MgO.zSiO2 where 2.970≦x≦3.500, 0.001≦y≦0.030, and 1.900≦z≦2.100 are satisfied,

• wherein a main peak is present in the range of diffraction angle 2θ=16.1 to 16.5 degree in the X-ray diffraction pattern obtained by measurement on the blue phosphor using an X-ray with a wavelength of 0.774 Å, and at least one condition of the following conditions (B1) and (B2) is satisfied:
• (B1) a peak or a group of peaks consisting of overlapping peaks whose top is or tops are located in the range of diffraction angle 2θ=15.3 to 16.1 degree is present, and the one-tenth value width of the peak or the group of peaks is not less than 0.13 degree and not more than 0.9 degree;
• and
• (B2) a peak or a group of peaks consisting of overlapping peaks whose top is or tops are located in the range of diffraction angle 2θ=22.2 to 23.3 degree is present, and the one-tenth value width of the peak or the group of peaks is not less than 0.18 degree and not more than 1.5 degree.