Exploring high-entropy design in rare-earth aluminum garnet scintillators

Cargo inspection via high-energy X-ray radiography is an important imaging modality for national security applications where 2-9 MeV X-rays are used to identify contraband through non-intrusive inspection. CdWO4 single crystal scintillator is a common detector material for this application, however, it suffers from a relatively low light yield and toxicity. As the need for this imaging capability grows, a search for new scintillator materials for this application is ongoing. In this work, single-component, multi-component, and high-entropy aluminum garnet ceramics are synthesized to investigate the effect configuration entropy has on the scintillation properties. In addition, the composition (Y,Gd,Tb,Lu)
3
Al
5
O
12
:Ce is investigated for use in high-energy X-ray radiography applications. Aluminum garnet powders are synthesized via a wet chemistry method and are densified into ceramics via uniaxial hot pressing. XRD measurements are done to confirm the phase purity of powders and ceramics. Scintillation properties such as light yield, decay time, and afterglow are evaluated. Radiation hardness is evaluated through the measurement of scintillation properties before and after irradiation with a ${ }^{60} \mathrm{Co}$ source. It is found that afterglow is suppressed in the compositions with greater configurational entropy.