A none-rare earth elements-based Mn2+-doped MgAl2O4 green phosphor for LED applications was synthesized by a solid-state reaction method. X-ray diffraction analysis revealed that the synthesized phosphors have a spinel-type MgAl2O4 phase and any secondary phase formed by the Mn2+ addition was not detected. The prepared MgAl2O4:Mn2+ phosphors showed a single intense broadband green emission in the range from 500 to 560 nm excited by near UV to visible blue light. The green emission mechanism was found to be attributed to the spin-forbidden d-d transition (4T1(4G)→ 6A1(6S)) of Mn2+ by a schematic investigation in terms of energy transfer in Mn2+ ion. As the Mn2+ concentration increased, the emission intensity increased up to 3.0 mol% and then decreased at higher concentrations as a result of concentration quenching, while the peak wavelength continuously moved to the longer wavelengths. Dynamic light scattering (DLS) and field-effect scanning electron microscopy (FE-SEM) characterization showed the 3 mol% Mn2+-doped MgAl2O4 phosphor particles have an irregularly round shape and uniform size distribution with an average particle size of 1-2 μm.

Keywords: MgAl2O4:Mn2+ phosphors, Solid-state reaction, Green phosphors, Optical properties, LEDs.