Synergistic Effects of Lattice Stability and Frenkel Defects Designed for Anti‐Thermal Quenching X‐Ray Scintillators

ABSTRACT X‐ray scintillators have attracted widespread attention in medical imaging, nondestructive testing, and high‐energy physics research. However, the thermal quenching effect caused by high temperatures significantly affects the radioluminescence (RL) efficiency of these materials at elevated temperatures, ultimately limiting their applications in high‐temperature environments. To address this critical issue, we developed an alkali metal rare earth fluoride material, Rb 2 TbF 5 , which exhibits unprecedented anti‐thermal quenching behavior, with its RL intensity at 720 K reaching 137% of that at 300 K. This is mainly attributed to the stable crystal structure of Rb 2 TbF 5 and the relatively low phonon energy of the fluoride host, both of which provide a favorable basis for maintaining RL at elevated temperatures. More importantly, first‐principles calculations demonstrate that the Frenkel defects formed in Rb 2 TbF 5 under X‐ray irradiation can effectively compensate for charge loss at high temperatures through a charge compensation mechanism. Finally, the Rb 2 TbF 5 scintillator demonstrates an impressively low detection limit (684.8 nGy s −1 ) under X‐ray excitation and excellent fatigue resistance (temperature: 720 K, cycle number: 60, RL intensity retention of 99%), highlighting its potential for applications in extreme environments. This study provides new insights into the development of scintillator materials suitable for high‐temperature environments.