Far-red emitting Mg2La3NbO9:Mn4+ powder phosphor: Synthesis and luminescence properties
Novel Mg 2 La 3 NbO 9 :Mn 4+ powder phosphors are successfully synthesized by the high-temperature solid-state reaction method under ambient air. The crystal structure, morphology, decay lifetimes, time-resolved emission spectra, and luminescence properties are investigated. The excitation spectrum of Mg 2 La 3 NbO 9 :Mn 4+ phosphor monitored at 708 nm is observed in the region from 210 nm to 600 nm. Mg 2 La 3 NbO 9 :Mn 4+ phosphor with excitation at the ultraviolet (UV) and blue light can emit the far-red emission with the emission band peaking at ~708 nm because of the 2 E → 4 A 2 transition of Mn 4+ and the corresponding chromaticity coordinates (0.7322, 0.2678). The optimal doping concentration of Mn 4+ ion is ~0.6 mol%. The decay lifetime of Mg 2 La 3 NbO 9 :xMn 4+ phosphors decrease from 1.143 ms to 1.099 ms with increasing the Mn 4+ ion concentration from 0.2 mol% to 1.0 mol%. The good thermal stability of Mg 2 La 3 NbO 9 :Mn 4+ phosphor is confirmed by the temperature-dependent emission spectra. The luminous mechanism of Mg 2 La 3 NbO 9 :Mn 4+ phosphor is explained by using the Tanabe Sugano energy level diagram of Mn 4+ ion. All the experimental results imply that Mg 2 La 3 NbO 9 :Mn 4+ phosphor has a potential application in the white light-emitting diodes (LEDs) field.
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