Design, synthesis and characterization of an orange-yellow long persistent phosphor: Sr_3Al_2O_5Cl_2:Eu^2+,Tm^3+

A novel orange-yellow emitting Sr3Al2O5Cl2:Eu(2+), Tm(3+) phosphor with bright and long persistent luminescence (LPL) has been newly developed. The incorporation of Tm(3+) into the Sr3Al2O5Cl2:Eu(2+) as an auxiliary activator dominates its long persistent luminescence and thermoluminescence characteristics to a large extent. The emissions in Sr3Al2O5Cl2:Eu(2+), Tm(3+) for both fluorescence and LPL are due to the 5d → 4f transitions of Eu(2+). The orange-yellow long persistent luminescence with the chromaticity coordination of (0.53, 0.46) can persist for nearly 220 min at recognizable intensity level (≥ 0.32 mcd/m2). This investigation provides a new and efficient long persistent phosphor which enriches the color of the existing LPL.