A series of SrAl2O4: Eu2+, Dy3+ long-afterglow (LAG) phosphors with varying concentration of Li+, Na+ and K+, has been synthesized. The increased concentration of the three types of alkaline ions does not decrease the quantity of the total luminescent phases (SrAl2O4 plus Sr4Al14O25), but a different set of secondary phases has been evoluted for the K+-added series due to the failure of the incorporation of relatively large K+ (1.38 Å) to the Sr2+ (1.18 Å) site in the hosts, unlike the cases of smaller Li+ (0.76 Å) and Na+ (1.02 Å) ions. PL excitation, PL emission, and LAG luminescence, are decreased by all investigated alkaline ions, which would be due to the diminished incorporation of Eu2+ and Dy3+ activators into the luminescent hosts by the alkaline ions. For the cases of the Li+ and Na+-added series, the incorporated Li+ or Na+ to the luminescent hosts would also limit the activation of Eu2+ and charge trapping/detrapping of Dy3+ to yield the diminished PL properties and LAG luminescence. The type of defect complex formed by the addition of Li+ and Na+ ions has been deduced and compared with that formed when no alkaline ion is added
