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

Abstract

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, CeS_c1 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:0.02Ce³⁺,0.03Mn²⁺ 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.