Preparation,structure, luminescence properties of europium doped zinc spinel structure green-emitting phosphor ZnAl2O4:Eu2+

The Zn_1–xAl₂O₄:xEu²⁺ phosphor powders were synthesized by the solid-state reaction method. The synthesis temperature for ZnAl₂O₄ was optimized, whereas the phase structure, TEM images, photoluminescence (PL) properties, the concentration quenching mechanism, the fluorescence decay curves, as well as the CIE chromaticity coordinates of the samples were investigated in details. Under the excitation at 379 nm, the phosphor exhibits an asymmetric broad-band green emission with a peak at 532 nm, which is ascribed to the 5d–4f transition of Eu²⁺. When the doping concentration of Eu²⁺ ions is 0.01, the luminescence intensity of the sample reaches the maximum value. It is further proved that the exchange interaction results in the concentration quenching of Eu²⁺ in the Zn_1–xAl₂O₄:xEu²⁺ phosphor powders. The thermal quenching property of ZnAl₂O₄:Eu²⁺ phosphor was investigated and the quantum efficiency (QE) values of the selected Zn_0.99Al₂O₄:0.01Eu²⁺ phosphor was measured and determined as 54.85%. The lifetime of the optimized sample Zn_0.99Al₂O₄:0.01Eu²⁺ is 3.0852 μs and the CIE coordinate of the sample was calculated as (0.3323, 0.5538) with high-color-purity green emission. All properties indicate that the green-emitting ZnAl₂O₄:Eu²⁺ phosphor powder has potential application in white LEDs.