Unveiling the Formation of Inclusions and Their Impact on Scintillation Performance in Sr Codoped LaBr₃:5%Ce Crystals

Sr²⁺ codoped LaBr₃:Ce³⁺ scintillation crystals exhibit exceptional performance in various radiation detection applications, achieving near-theoretical energy resolution (2%) through optimized codoping strategies. However, the substantial doping concentrations required (0.35–0.7 mol %) introduce significant challenges in crystal growth, particularly defect formation, which limits large-scale production and practical application. Herein, this study investigates SrBr₂-induced defect dynamics during crystal growth with a focus on the role of inclusion defects in degrading scintillation performance. The inclusion density increases along the crystal growth direction and follows the matrix-controlled morphological evolution, eventually forming well-defined polyhedral morphologies with equilibrium hexagonal prism bounded by {1000} and {1010} facets. Constitutional supercooling-induced interface instabilities emerge as the primary mechanism driving inclusion formation. Crucially, increasing inclusion density along the growth direction leads to enhanced photon scattering, significantly reducing transmittance, light output, and energy resolution─from 2.69 to 5.9%. In addition, the scattering of scintillation photons by inclusion introduced an additional slow decay component in the scintillation time profile. By leveraging these insights, we optimized growth parameters to suppress this instability, achieving improved crystal quality with an energy resolution of 2.44%@662 keV─a significant improvement compared to conventional methods. These observations quantitatively reveal the influence of macroscopic inclusions, establish a comprehensive framework for macroscopic defect engineering in LaBr₃-based scintillators, and further provide effective strategies for control and optimization of metal halide scintillators.