Long lasting phosphorescence of Sr4Al14O25:Eu,Dy thin films by magnetron sputtering

This paper reports the preparation process and the long lasting phosphorescence of the Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ thin films obtained by magnetron sputtering. Phosphorescence was achieved by annealing the films in reducing atmosphere. Sr₄Al₁₄O₂₅ thin film was obtained when the films were treated at 1200 °C, while SrAl₂O₄ was generated as the intermediate phase during the annealing process. Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film generated an emission at 485 nm, and SrAl₂O₄:Eu²⁺,Dy³⁺ film showed an emission peaking at 515 nm. Afterglow characteristics were observed for both films, and Sr₄Al₁₄O₂₅:Eu²⁺,Dy³⁺ film showed a better afterglow property than the SrAl₂O₄:Eu²⁺,Dy³⁺ film due to a deeper trap level and a higher trap concentration formed in the thin films.