We report the long-lasting bluish-green phosphorescence for X-ray or cathode ray tubes in the phosphors with compositions of either Ba2SiO4:0.01Eu2+–xSi3N4 (x=0–1) or 2BaCO3–ySi3N4:0.01Eu2+(y=1/6–1) synthesized by a solid-state reaction. By tuning the Si3N4content, 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 2BaCO3–ySi3N4:0.01Eu2+ is attributed to N substitution for O to generate a shallow trap. In Ba2SiO4:0.01Eu2+–xSi3N4 , 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.
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