Effect of Condition of Preparation on Long-Lasting Afterglow Characteristics of Eu-Dy-Codoped Sr4Al14O25 Phosphor
Nobuyuki TAKEUCHI, Keisuke OGASAWARA, Takuya YAMADA and Hisayoshi KOBAYASHI
Abstract:Eu, Dy-codoped Sr4Al14O25 phosphors were prepared with B2O3 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 Sr4Al14O25 was synthesized at the samples added with small amount of B2O3 (B/Sr=0.2), but the impurity phase was also observed at the samples added with large amount of B2O3 (B/Sr=0.7). The emission wavelength of the sample added with large amount of B2O3 shifted to shorter wavelength than that of the sample added with small amount of B2O3. 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. Key Words:Photoluminescence, Strontium aluminates, ESR, Reducing atmosphere, Long-lasting afterglow