Preparation and Luminescence of ZnAl2O4:Mn Phosphors

Nano-sized manganese-doped zinc aluminate spinel (Zn1-xMnxAl2O4; x = 0-6.0 mol%) powder phosphors were prepared by the sol gel process. Zinc chloride, aluminum isopropoxide, and manganese chloride were employed as precursors. The influences of manganese concentration and heat treatment conditions on the crystallization and photoluminescence of the phosphors were investigated. The dried powders were amorphous to X-ray powder diffraction (XRD) and the single-phase ZnAl2O4 spinel crystallite started to form at temperatures as low as 600 degrees C. The crystallization of powder did not significantly affected by various manganese concentrations. On heating at 1000 degrees C, the resulting powder phosphors had the average crystallite and primary particle sizes of around 20-25 and 20-30 nm, respectively, depending on the dopant content and heating time. Photoluminescence spectra exhibited strong green emission bands centered at 512 nm under an excitation wavelength of 458 nm. The luminescence efficiency has been investigated as a function of dopant content, heating temperature, heating time, and specific surface area of the powders.