Flexible Ba 2 LuTaO 6 :Tb 3+ /Eu 3+ Perovskites with Multicolor Luminescence and Photochromism for X‐Ray Imaging, Visual Dosimetry, and Encryption

ABSTRACT With the rapid development of X‐ray technologies in medical imaging, non‐destructive testing, and anti‐counterfeiting, there is an urgent demand for multimode visual detection. Here, Tb 3+ /Eu 3+ ‐doped Ba 2 LuTaO 6 perovskites were synthesized via solid‐state reaction, showing distinct green and red emissions under UV or X‐ray excitation, with co‐doping enabling tunable yellow‐to‐red luminescence. Eu 3+ ‐doped Ba 2 LuTaO 6 exhibited reversible X‐ray‐induced photochromism with nearly full thermal recovery (200°C, 5 min) and a 68% photoluminescence modulation depth. The photochromic response enabled cumulative visual dosimetry, while radioluminescence intensity scaled linearly with dose rate, supporting real‐time monitoring. Different dopants yielded distinct colors and markedly different light yields, enabling color‐visualized dose detectors for radiation warning. Mechanistic studies confirmed oxygen‐vacancy‐related color centers as the origin of photochromism and multipolar energy transfer as the basis of tunable luminescence. Incorporation of phosphors into polydimethylsiloxane produced flexible scintillator films for high‐resolution X‐ray 3D imaging. A proof‐of‐concept encryption system, integrating luminescence modulation and X‐ray imaging, further demonstrated strong anti‐counterfeiting performance. This multifunctional platform advances flexible imaging, radiation detection, and secure information encryption.