Deep-red emission of Mn4+ and Cr3+ in (Li1−xAx)2MgTiO4 (A=Na and K) phosphor: Potential application as W-LED and compact spectrometer

Mn4+ doped and Mn4+/Cr3+ co-doped alkali metal titanate phosphors have been prepared by solid state reaction method. A part of Li+ ions in the Li2MgTiO4: Mn4+ are substituted with Na+ and K+ ions and consequently the intensity of Mn4+ emission at 678 nm is enhanced by 1.7 and 2.5 times, respectively. In the Mn4+/Cr3+ co-doped (Li0.95K0.05)2MgTi0.999O4, both emission of Cr3+at 726 nm and emission of Mn4+ at 678 nm of Mn4+ are observed. It is interesting to find that the intensity ratio of 726-678 nm emissions in the Mn4+/Cr3+ phosphor continually increases with excitation wavelength increasing from 290 nm to 455 nm, which means that the intensity ratio in turn can be used to identify the excitation light wavelength. This refers a possible approach to design novel compact light-wavelength detector or spectrometer based on the phosphor. The mechanism of Na+ or K+ substitution induced luminescence enhancement in the Mn4+ phosphor and the competition between the Cr3+ and Mn4+ emissions in the Mn4+/Cr3+ co-doped has been discussed.