Thermally Activated Delayed Mechano‐ and Radioluminescence Enabling Long‐Term and Time‐Delayed Spatiotemporal Stress and X‐ray Imaging

ABSTRACT Current stress visualization techniques face limitations due to the transient signal capture of traditional mechanoluminescent (ML) materials, restricting the retrieval of historical mechanical data and hindering long‐term damage diagnosis for high‐end equipment. This study overcomes these constraints by precisely regulating trap energy levels in β ‐Ca ₃ (PO ₄ ) ₂ : Dy through gradient Li ⁺ doping, resulting in significantly enhanced thermally delayed luminescence performance under mechanical or X‐ray excitation. Lattice distortion and charge compensation from Li ⁺ aggregation increase trap density, extending spatiotemporal imaging signal traceability beyond 45 days. Notably, the triboelectric effect at the organic–inorganic interface triggered by mechanical stimulation not only induces transient ML but also facilitates the capture of charge carriers at intrinsic defect states of phosphors. Inspired by static high‐energy X‐ray imaging based on trap filling, by employing passive mechanical responses for trap filling and thermal activation for delayed carrier release, dynamic stress distribution is visually monitored, overcoming conventional ML's rapid signal decay. Experimental and theoretical results confirm that high‐energy stimulation ionizes oxygen vacancies into paramagnetic states, enabling electron capture and thermally activated release. The proposed self‐capture and thermal‐delay response technology offers an innovative strategy for precise damage localization in high‐speed collisions, creating a new pathway for static/dynamic defect tracking in advanced equipment.