Color tunable single-phase Eu2+ and Ce3+ co-activated Sr2LiAlO4 phosphors

Abstract

High purity Eu2+ and Ce3+ singly and co-activated Sr2LiAlO4 phosphors were successfully synthesized through a facile combustion reaction. Fabrication of color tunable, single-phase phosphors was achieved by varying the Eu2+/Ce3+ ratio that utilized the energy transfer between Ce3+ and Eu2+. For the singly activated compositions, the highest quantum efficiencies were 25% and 40% for Sr1.998Eu0.002LiAlO4 and Sr1.998Ce0.002LiAlO4, respectively. The emission of Sr2LiAlO4:Ce3+ and the excitation of Sr2LiAlO4:Eu2+ overlap in the range of 400 nm-500 nm, so that energy transfer from Ce3+ -> Eu2+ takes place. The emission color of Eu2+ and Ce3+ co-activated Sr2LiAlO4 changes from blue, to cool-white, to green depending on the activator concentrations. The maximum quantum efficiency of Eu2+ and Ce3+ co-activated Sr2LiAlO4 was 55%, a 40% increase over the singly activated phosphors, which demonstrates that the quantum efficiency improves by co-activation.