Structural and Luminescent Properties of Mg_0.25−xAl_2.57O_3.79N_0.21:xMn²⁺ Green-Emitting Transparent Ceramic Phosphor

A series of spinel-type Mg_0.25−xAl_2.57O_3.79N_0.21:xMn²⁺ (MgAlON:xMn²⁺) phosphors were synthesized by the solid-state reaction route. The transparent ceramic phosphors were fabricated by pressureless sintering followed by hot-isostatic pressing (HIP). The crystal structure, luminescence and mechanical properties of the samples were systematically investigated. The transparent ceramic phosphors with tetrahedrally coordinated Mn²⁺ show strong green emission centered around 515 nm under blue light excitation. As the Mn²⁺ concentration increases, the crystal lattice expands slightly, resulting in a variation of crystal field and a slight red-shift of green emission peak. Six weak absorption peaks in the transmittance spectra originate from the spin-forbidden ⁴T₁(⁴G)→⁶A₁ transition of Mn²⁺. The decay time was found to decrease from 5.66 to 5.16 ms with the Mn²⁺ concentration. The present study contributes to the systematic understanding of crystal structure and properties of MgAlON:xMn²⁺ green-emitting transparent ceramic phosphor which has a potential application in high-power light-emitting diodes.