Luminescence and Structural Characterization of Gd2O2S Scintillators Doped with Tb3+, Ce3+, Pr3+ and F for Imaging Applications

Radiodiagnostic technologies are powerful tools for preventing diseases and monitoring the condition of patients. Medicine and sectors such as industry and research all use this inspection methodology. This field demands innovative and more sophisticated systems and materials for improving resolution and sensitivity, leading to a faster, reliable, and safe diagnosis. In this study, a large characterization of gadolinium oxysulfide (Gd2O2S) scintillator screens for imaging applications has been carried out. Seven scintillator samples were doped with praseodymium (Pr3+), terbium (Tb3+) activators and co-doped with praseodymium, cerium, and fluorine (Gd2O2S:Pr,Ce,F). The sample screens were prepared in the laboratory in the form of high packing density screens, following the methodology used in screen sample preparation in infrared spectroscopy and luminescence. Parameters such as quantum detection efficiency (QDE), energy absorption efficiency (EAE), and absolute luminescence efficiency (ALE) were evaluated. In parallel, a structural characterization was performed, via XRD and SEM analysis, for quality control purposes as well as for correlation with optical properties. Spatial resolution properties were experimentally evaluated via the Modulation Transfer Function. Results were compared with published data about Gd2O2S:Pr,Ce,F screens produced with a standard method of a sedimentation technique. In particular, the ALE rose with the X-ray tube voltage up to 100 kVp, while among the different dopants, Gd2O2S:Pr exhibited the highest ALE value. When comparing screens with different thicknesses, a linear trend for the ALE value was not observed; the highest ALE value was measured for the 0.57 mm thick Gd2O2S:Pr,Ce,F sample, while the best MTF values were found in the thinner Gd2O2S:Pr,Ce,F screen with 0.38 mm thickness.