Synthesis of SrAl₂O₄: Eu, Dy-based phosphors by coprecipitation and characterization of their photoluminescence

In this study, the long photoluminescence phosphor, SrAl₂O ₄: Eu²⁺,Dy³⁺ was synthesized by a coprecipitation method in which metal salts of Sr(NO₃)₂, Al(NO₃)₃. 9H₂O, were dissolved in a (NH ₄)₂CO₃ solution with Eu(NO₃) ₃-5H₂O and Dy(NO₃)₃-5H₂O added as an activator and co-activator, respectively. The coprecipitated products were separated from the solution, washed, dried in a vacuum and heated at 800-1400 °C for 3 h under a reducing ambient atmosphere of 95%Ar+5%H ₂. For the synthesized SrAl₂O₄: Eu ²⁺Dy³⁺ the properties of photoluminescence such as emission, excitation and decay time were examined. Monitored at 520 nm, the excitation spectrum showed a maximum peak intensity at 313 nm with a broad band from 200-500 nm. The shift of main peaks of excitation toward shorter wavelengths for the phosphors prepared by the coprecipitation method occurred due to the quantum size effect of the nano-sized particles, compared with those produced by the solid-state reaction method. The emission intensity increased as the annealing temperature increased and showed a maximum peak intensity at 510 nm with a broad band from 400-650 nm. The decay time of SrAl₂O ₄: Eu²⁺Dy³⁺ increased as the heat treatment temperature increased.