Flexible Scintillation Films Based on Ni Co-doped LiLuF₄:Tb for High-Resolution X-ray and Thermoluminescence Dual-Mode Imaging

Abstract

LiLuF4 microcrystalline scintillation materials possess several advantages, including high chemical stability, simplified fabrication processes, and tunable emission wavelengths. These materials demonstrate significant potential in fields such as X-ray imaging, biodiagnostics, photodynamic therapy, advanced anti-counterfeiting, and thermally activated delayed imaging. However, the relatively weak radioluminescence intensity of single rare-earth-doped LiLuF4 crystals has constrained their practical applications. In this work, Ni2+ co-doped LiLuF4:Tb microcrystalline scintillators are synthesized via a hydrothermal method. The incorporation of heterovalent Ni2+ ions effectively enhanced both the radioluminescence and thermoluminescence intensities of the LiLuF4 microcrystals. After doping of 3 mol% Ni2+ ions, the radioluminescence intensity is increased by 125.34%. The X-ray detection limit of LiLuF4:Tb, Ni reaches 3.7966 nGy·s‒1, which is considerably lower than the medical imaging requirements of 5.5 μGy·s‒1. Furthermore, a large-area flexible composite scintillation film of dimensions 80 mm × 145 mm is prepared to achieve high spatial resolution X-ray imaging of 25 LP/mm@20%MTF, indicating that heterovalent-doped fluoride scintillators possess exceptional application potential.