Bright and Thermally Stable LYSGO:Ce Scintillators Enabled by Crystal Field and Defect Engineering for High‐Resolution X‐Ray Imaging

Cerium‐doped lutetium yttrium oxyorthosilicate (LYSO:Ce) is a benchmark scintillator for gamma‐ray detection, yet the long‐standing trade‐off among light yield, afterglow, and spatial resolution limits its transition into high‐definition X‐ray imaging. Here, an isovalent Ge substitution strategy is proposed to construct a high‐performance (Lu,Y) 2 (Si,Ge)O 5 :Ce (LYSGO:Ce) scintillator. Structurally, Ge incorporation selectively distorts the [REO 6 ] polyhedron, deepening the 5d emitting state of Ce 3+ centers located at these six‐coordinate sites (denoted as Ce2 centers) to create a thermodynamically favorable well for enhanced carrier capture. Concurrently, intrinsic lattice traps are effectively passivated. This synergistic mechanism delivers a high light yield of 38,700 photons MeV −1 (∼27% improvement), an afterglow reduction by nearly an order of magnitude, and a thermal quenching threshold (T 50 ) extended by over 60 K. Crucially, the 1.0 mm‐thick single‐crystal screen achieves an exceptional spatial resolution of 25.6 lp mm −1 due to enhanced photon statistics and suppressed afterglow background, while maintaining reliable structural resolvability at 473 K. This work provides a physical paradigm for designing ultrabright, resilient scintillators for high‐flux medical CTs and high‐temperature industrial non‐destructive testing.