We report the long-lasting bluish-green phosphorescence for X-ray or cathode ray tubes in the phosphors with compositions of either Ba2SiO4:0.01Eu(2+)-xSi(3)N(4) (x=0-1) or 2BaCO(3)-ySi(3)N(4):0.01Eu(2+) (y=1/6-1) synthesized by a solid-state reaction. By tuning the Si3N4 content, the phosphorescence may originate from Eu2+ in BaSi2O2N2 (peaking at 490 nm), Ba2SiO4 (505 nm), and Ba3SiO5 (590 nm) phases. The strong phosphorescence of the Ba2SiO4:Eu2+ phase in 2BaCO(3)-ySi(3)N(4):0.01Eu(2+) is attributed to N substitution for O to generate a shallow trap. In Ba2SiO4:0.01Eu(2+)-xSi(3)N(4), however, N prefers reacting with Ba2SiO4 to form BaSi2O2N2, thereby exhibiting a strong phosphorescence of the BaSi2O2N2:Eu2+ phase but a weak phosphorescence of the Ba2SiO4:Eu2+ phase.