Single-phased emission-tunable Mg-doped ZnO phosphors for white LEDs

A simple and low-cost approach is presented to tune the visible emission of Mg-doped ZnO phosphors obtained in a two-stage annealing process. The products of this process were characterized via X-ray diffraction, scanning electron microscopy and fluorescence measurements. The results indicate that the second annealing time has a significant influence on the particle size and structure of the samples, and the visible emission of Mg-doped ZnO phosphors is tunable in a wide range from blue to red by changing the second annealing time. The defect emission of phosphors exhibiting strong dependence on annealing time suggests that visible emission would be more consistent with intrinsic defects than extrinsic defects. White emission was obtained for the phosphors annealed in a carbon monoxide reducing atmosphere for 30, 60, 180 and 300 min. The Commission International de l’Eclairage chromaticity of the 60-min annealed sample was determined to be (x = 0.27, y = 0.34), and Tc was observed to be 8929 K.