Eu, Dy -codoped Sr
4Al
14O
25 phosphors were prepared with B
2O
3 additives as flux at the temperature of 1300 to 1400°C for 3h in flowing hydrogen gas. These products were characterized by XRD analysis, ESR, UV-Vis spectroscopy and SEM. XRD analysis showed that single phase Sr
4Al
14O
25 was synthesized at the samples added with small amount of B
2O
3 (B/Sr = 0.2), but the impurity phase was also observed at the samples added with large amount of B
2O
3 (B/Sr = 0.7). The emission wavelength of the sample added with large amount of B
2O
3 shifted to shorter wavelength than that of the sample added with small amount of B
2O
3. The afterglow characteristics of both samples were comparable level. The intensity of emission spectra decreased and afterglow characteristics degraded in the samples cooled in argon gas in behalf of hydrogen. ESR measurement indicated that the change in optical properties of the sample cooled in argon gas due to the oxidation of Eu2+ in the phosphor by trace of oxygen in argon gas.
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