Li3Mg2NbO6:Mn4+ red phosphor for light-emitting diode: Synthesis and luminescence properties

Novel double perovskite Li 3 Mg 2 NbO 6 :Mn 4+ deep red-emitting phosphor is synthesized by solid-state reaction method in air. Emission band peaking at ∼670 nm with chromaticity coordinates (0.722, 0.278) is observed in the range of 600–780 nm due to 2 E →  4 A 2 transition of Mn 4+ ion. Excitation spectrum monitored at 670 nm contains three excitation bands peaking at ∼310, 395, and 470 nm within the range 220–600 nm, which indicate that Li 3 Mg 2 NbO 6 :Mn 4+ phosphor can be excited by ultraviolet, near ultraviolet, and blue light-emitting diode chips. The optimal Mn 4+ doping concentration is about 0.4 mol%. Fluorescence lifetime decreases from 0.485 to 0.32 ms with increasing Mn 4+ ion concentration from 0.2 to 1.2 mol%. Time resolved emission spectra and lifetime data confirm that there is only a single type of Mn 4+ ion luminescent center in Li 3 Mg 2 NbO 6 :Mn 4+ phosphor. The possible luminous mechanism of Mn 4+ ion is analyzed by Tanabe–Sugano energy diagram.