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 Sr_1.998Eu_0.002LiAlO₄ and Sr_1.998Ce_0.002LiAlO₄, 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.