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

The Zn1–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 Zn1–xAl2O4:xEu2+ phosphor powders. The thermal quenching property of ZnAl2O4:Eu2+ phosphor was investigated and the quantum efficiency (QE) values of the selected Zn0.99Al2O4:0.01Eu2+ phosphor was measured and determined as 54.85%. The lifetime of the optimized sample Zn0.99Al2O4:0.01Eu2+ 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.