Synthesis, Crystal Structure, and Photoluminescence Characteristics of High-Efficiency Deep-Red Emitting Ba2GdTaO6:Mn4+ Phosphors

In this article, a series of novel Mn4+-doped Ba2GdTaO6 (BGT) red-emitting phosphors were successfully synthesized via a high-temperature solid-state method. The crystal structure, morphology, and luminescent performance of the samples were investigated in detail with X-ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) spectra, decay curves, and internal quantum efficiency (IQE). Excited at 358 nm, these samples showed an intense deep-red emission band peaking at 688 nm in the wavelength region of 620–800 nm. The excitation spectra of these samples monitored at 688 nm exhibited two broad excitation bands from 250 to 600 nm with peaks at 358 and 469 nm. The systematic investigation of the concentration-dependent PL properties of BGT:Mn4+ phosphors revealed that the deep-red emission intensity reached the maximum when the Mn4+ doping concentration was 0.6 mol %. The critical distance (Rc) between Mn4+ ions for concentration quenching was 36.57 Å, and the major mechanism of energy transfer among Mn4+ activators in BGT:Mn4+ was dipole–dipole interaction. The decay lifetimes decreased from 0.285 to 0.248 ms with the increasing Mn4+ doping concentration from 0.2 to 1.2 mol %. The Commission Internationale de l’Éclairage coordinates of the optimal BGT:0.6%Mn4+ sample were (0.7294, 0.2706). The values of the IQE for all BGT:Mn4+ samples were measured, and the highest value could reach up to 62%. The above results revealed that these high-efficiency BGT:Mn4+ deep-red-emitting phosphors had promising potential for application in indoor plant growth lighting.