Abstract
In this paper, novel Li3Mg2TaO6:Mn4+ (LMT:Mn4+) red-emitting phosphors used for plant cultivation light-emitting diodes (LEDs) have been prepared via high-temperature solid-state reaction method. The LMT host material crystallized in to orthorhombic crystal system with a space group of Fddd and provided TaO6 octahedral sites for Mn4+ incorporation. Interestingly, these LMT:Mn4+ phosphors exhibited a broad excitation band ranging from 250 nm to 600 nm peaking at 349 nm and 469 nm, and it emits bright deep-red narrowband at 661 nm with a full width at half maximum (FWHM) of ~41 nm due to Mn4+:2Eg → 4A2g spin-forbidden transition. The optimal LMT:0.1%Mn4+ sample showed the strongest luminescence. The concentration quenching mechanism was determined to be a dipole-dipole interaction among Mn4+ ions, and the critical distance (Rc) was 59.81 Å. The decay lifetimes of LMT:Mn4+ phosphors ranged from 0.281 to 0.114 ms, and presented a reasonable downward trend with increasing Mn4+ concentration. Besides, the CIE chromaticity coordinates of LMT:0.1%Mn4+ phosphors were calculated to be (0.7192, 0.2807), locating in the deep-red region. The internal quantum efficiency reached up to 23%. Importantly, the deep-red emission band of LMT:Mn4+ phosphors matched well with the absorption band of phytochrome PR. These results suggested that the as-synthesized LMT:Mn4+ phosphors were potential deep-red phosphors for application in LEDs as artificial light source for indoor plant growth.
Published Version
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