Preparation, structural and optical characteristics of a deep red-emitting Mg 2 Al 4 Si 5 O 18 : Mn 4+ phosphor for warm w-LEDs

Abstract A novel red-emitting phosphor Mg 2 Al 4 Si 5 O 18 :Mn 4+ is successfully synthesized using a solid-state reaction method. Aluminosilicate Mg 2 Al 4 Si 5 O 18 of low-symmetry orthorhombic phase contains abundant octahedrons and is suitable for Mn 4+ doping. A broad absorption band ranging from 240 nm to 550 nm in the ultraviolet–visible spectra corresponds to the photoluminescence excitation spectrum. The emission spectrum from 650 nm to 750 nm exhibits a strong emission peak at 680 nm because of the 2 E g → 4 A 2g transition of Mn 4+ ion. The critical distance Rc for concentration quenching is ∼33.3 A, and the energy transfer mechanism is determined to be dipole–dipole interaction. Luminescence mechanism is analyzed using the energy level diagram of Mn 4+ ion. Racha parameters B and C are evaluated and used to discuss the nephelauxetic effect for the Mn 4+ ions in the Mg 2 Al 4 Si 5 O 18 . Temperature-dependent fluorescence test demonstrates the good thermal optical properties of the phosphor. An assembled light-emitting diode (LED) device with efficient luminescence demonstrates its practical use. Results indicate the potential application of the phosphor for white LEDs.