Screening Thermochromic Luminescent Materials in Cs‐Cd‐Br Ternary Phase Diagram for Temperature Visualization Applications

Abstract Thermochromic luminescent materials (TLMs) with spectral responsiveness to thermal stimuli have received broad attention due to the forefront applications in temperature visualization and sensing technologies. Herein, a phase diagram‐driven strategy for designing TLMs in Cs–Cd–Br ternary system is presented. The room temperature stable Cs 7 Cd 3 Br 13 crystal is first obtained by utilizing a facile hydrothermal method, and the self‐trapped exciton (STE) luminescence is improved by breaking local symmetry via Mg 2+ doping. Then thermochromic luminescence is further realized in Mn 2+ co‐doped Cs 7 Cd 3 Br 13 on the basis of reversible structural transition to metastable Cs 2 CdBr 4 under thermal stimuli. The emission color change from bright yellow to green benefits from the variation of crystal fields around Mn 2+ , which can be switched by heating and cooling circulations. Finally, the resulting material is used as a demo to visualize the temperature of a homemade high‐frequency induction heating sintering platform.