Enhanced Thermal Stability and Energy Transfer by Crystal‐Field Engineering in a Garnet Phosphor for Thermometry and NIR‐LED
Luhui Zhou, Zeyu Lyu, Dashuai Sun, Sida Shen, Taixing Tan, Lixuan Wang, Hanwei Zhao, Hongpeng You
Abstract
Abstract It is of significant importance to tailor the luminescent properties of Cr 3+ ions as efficient near‐infrared (NIR) emitter for extended optical applications. Here, crystal field engineering is explored to tailor the luminescent properties of a Cr 3+ ‐doped garnet, Lu 2 Ca 1 ‐ x Sr x Al 4 SiO 12 ( x = 0–1). As Ca 2+ is substituted by Sr 2+ , the emission of Cr 3+ becomes sharper with longer lifetime, indicating that the 2 E g → 4 A 2g transition becomes dominant. More importantly, the thermal stability is greatly improved, as the emission intensity at 480 K increases from 83% to 111% of that at 300 K. Moreover, the efficiency of the energy transfer from the Cr 3+ to Yb 3+ /Nd 3+ increases from 60–70% to 80–90%. The intensity ratio of I 810 / I 706 from the Lu 2 SrAl 4 SiO 12 :Cr 3+ ,Nd 3+ can be applied to thermometry, with the maximum relative sensitivity value of 1.43% K –1 at 303 K. Compared with the blue emission from light‐emitting diode (LED) chip, a clearer and more accurate imaging is established with NIR emission from Cr 3+ . Furthermore, the intensity ratio of the emissions from the Cr 3+ and Yb 3+ ions is applied to differentiate pork, chicken, and beef. These findings provide an avenue to optimize the thermal stability and energy transfer of Cr 3+ ‐activated NIR emitters for the applications in thermometry and NIR‐LED.