Scalable Synthesis of Cs ₂ NaYCl ₆ :Tb ³⁺ Scintillators Toward Cutting‐Edge X‐Ray Radiography

Abstract Scintillators that convert high‐energy X‐ray photons into visible light are indispensable for a broad range of imaging applications. However, the development of high‐performance scintillators combining high light yield, excellent stability, and scalable processability remains a significant challenge. Here, a simple, low‐temperature, and scalable “dissolution‐drying” strategy is presented for the synthesis of lead‐free Cs 2 NaYCl 6 :Tb 3+ double perovskite scintillators with outstanding performance. Taking advantage of the highly symmetric elpasolite structure and the efficient incorporation of Tb 3+ ions, the resulting microcrystals achieve a high light yield (≈62 359 photons MeV −1 ), exceptional radiation resistance, an ultralow detection limit (15.19 nGy s −1 ), and remarkable thermal stability up to 773 K. By incorporating the microcrystals into a polydimethylsiloxane (PDMS) matrix, flexible scintillator films are fabricated, demonstrating superior mechanical durability and high‐resolution X‐ray imaging capability (>24 lp mm −1 ). These findings enable large‐scale scintillator production and advance next‐generation X‐ray radiography, offering high sensitivity, stability, flexibility, and versatility for advanced radiographic systems and future optoelectronic applications.