Density-functional theory calculations, luminescence properties and fluorescence ratiometric thermo-sensitivity for a novel borate based red phosphor: NaBaSc(BO3)2:Ce3+,Mn2+

In this work, a novel borate based red phosphor NaBaSc(BO3)(2) (NBS):Ce3+,Mn2+ was designed and successfully synthesized by a solid-state reaction. The formation energies of four different substitutional defects Ce-Ba, Ce-Na, CeSc1 and Ce-Sc2 were calculated by density-functional theory (DFT) calculations. In the meantime, Ce3+ ions occupying three different crystalline sites (Ba, Na and Sc1/Sc2) were analyzed by combining Gaussian fitting and Time-Resolved PhotoLuminescence (TRPL) mapping. On the other side, based on the effective energy transfer from Ce3+ to Mn2+, NBS:Ce3+,Mn2+ shows a broad absorption in the UV region (240 to 420 nm) and the emission intensity of Mn2+ is greatly improved (about 130 times than that of NBS:Mn2+). The mechanism of energy transfer from Ce3+ to Mn2+ was defined as dipole-dipole interaction by the Inokuti-Hirayama model. In addition, a white LED lamp with a good color rendering index (84.36) and a low color temperature (3784 K) was manufactured by using a 380 nm UV LED chip with a blend of BaMgAl10O17:Eu2+, (Sr,Ba)SiO4:Eu2+ and NBS:Ce3+,Mn2+. Meanwhile, under 370 nm excitation, the fluorescent intensity ratio of NBS:0.02Ce(3+),0.03Mn(2+) shows a linear correlation in the range of temperature from 298 K to 473 K with a high sensitivity of 3.16% K-1. Above all, our results provide a novel reference to develop Mn2+-based phosphors and an effective way to analyse the distribution of the doped elements in these compounds.