Thermally Enhanced Radioluminescent Materials With Three‐Dimensional Negative Thermal Expansion

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Conventional inorganic scintillators suffer from severe thermal quenching at elevated temperatures, severely limiting their application in high‐temperature radiation detection. Herein, a three‐dimensional (3D) negative thermal expansion (NTE) scintillator, Lu 2 (WO 4 ) 3 :Eu 3+ (LWO:Eu), is reported, which exhibits continuous radioluminescence (RL) thermal enhancement upon X‐ray excitation from 313 to 573 K. Unlike positive thermal expansion materials, LWO:Eu contracts volumetrically with an exceptionally large NTE coefficient (α v = −24.22 × 10 −6 /K), uniformly shortening the atomic distances between heavy atoms (W) and luminescent centers (Eu 3+ ). This unique 3D NTE behavior fundamentally boosts energy transfer efficiency from WO 4 2− to Eu 3+ at high temperatures, as further evidenced by in situ temperature‐dependent XRD and Raman analyses. Consequently, LWO:Eu achieves a record‐high light yield of 64839 photons/MeV at 573 K and an ultralow detection limit of 38.2 nGy/s, with a 4.5‐fold thermally enhanced red emission ( 5 D 0 → 7 F 2 ). A room‐temperature X‐ray imaging resolution of 22 l p/mm and successful scintillation imaging at 473 K is demonstrated, far outperforming commercial scintillators such as BGO, CsI:Tl, and LYSO:Ce. This work establishes a new paradigm for thermally enhanced RL materials based on 3D NTE, offering great promise for extreme‐environment applications including nuclear reactor monitoring, oil well logging, aerospace exploration, and high‐energy physics.