Enhance luminescence by introducing alkali metal ions (R+ = Li+, Na+and K+) in SrAl2O4:Eu3+phosphor by solid-state reaction method

In the present article, the role of charge compensator ions (R+ = Li+, Na+ and K+) in europium-doped strontium aluminate (SrAl2O4:Eu3+) phosphors was synthesized by the high-temperature, solid-state reaction method. The crystal structures of sintered phosphors were in a monoclinic phase with space group P21. The trap parameters which are mainly activation energy (E), frequency factor (s) and order of the kinetics (b) were evaluated by using the peak shape method. The calculated trap depths are in the range from 0.76 to 0.84 eV. Photoluminescence measurements showed that the phosphor exhibited emission peak with good intensity at 595 nm, corresponding to 5D0–7F1 (514 nm) orange emission and weak 5D0–7F2 (614 nm) red emission. The excitation spectra monitored at 595 nm show a broad band from 220 to 320 nm ascribed to O–Eu charge-transfer state transition and the other peaks in the range of 350–500 nm originated from f–f transitions of Eu3+ ions. The strongest band at 394 nm can be assigned to 7F0–5L6 transition of Eu3+ ions due to the typical f–f transitions within Eu3+ of 4f6 configuration. The latter lies in near ultraviolet (350–500 nm) emission of UV LED. CIE color chromaticity diagram and thermoluminescence spectra confirm that the synthesized phosphors would emit an orange-red color. Incorporating R+ = Li+, Na+ and K+ as the compensator charge, the emission intensity of SrAl2O4:Eu3+ phosphor can be obviously enhanced and the emission intensity of SrAl2O4:Eu3+ doping Li+ is higher than that of Na+ or K+ ions.