Red-tunable LuAG garnet phosphors via Eu3+→Mn4+ energy transfer for optical thermometry sensor application

Abstract

Currently, the development of excellent red phosphor materials has attracted much attention in daily lighting, backlit displays, optical thermometry sensors and plant growth fields. However, spectral peak position modulation and bandwidth are still crucial challenges. Herein, we design Eu³⁺→Mn⁴⁺ energy transfer in the Lu₃Al₅O₁₂ (LuAG) garnet host. On the one hand, photoluminescence tuning from narrow orangish-red emission (593 nm) to narrow deep-red light (668 nm) is successfully obtained, and the energy transfer efficiency reaches 47%. On the other hand, LuAG:Eu³⁺ exhibits anti-thermal-quenching properties; that is, the peak intensity reaches 166% at 200 °C of the initial intensity at 25 °C. By designing Eu³⁺→Mn⁴⁺ energy transfer, Mn⁴⁺ thermal quenching performance is dramatically improved. The photoluminescence peak intensities at 668 nm for LuAG:0.01Mn⁴⁺ and LuAG:0.05Eu³⁺,0.01Mn⁴⁺ retain 3.26% and 26% at 200 °C of the original intensity at 25 °C. The corresponding energy transfer mechanism to improve thermal quenching is revealed. According to the fluorescence intensity ratio technique, the maximum values of S_a and S_r for LuAG:0.05Eu³⁺,0.01Mn⁴⁺ are 0.07 K⁻¹ and 0.7% K⁻¹ at 303 K. The temperature sensitivity calculation indicates that LuAG:Eu³⁺,Mn⁴⁺ phosphors can act as promising candidates in optical thermometry sensors. This work provides an insight to achieve narrow red emission modulation and thermal quenching improvement.