Comparative investigation of transparent polycrystalline ceramic and single crystal Lu3Al5O12:Ce scintillators: Microstructural and thermoluminescence analyses

Lu3Al5O12:Ce (LuAG:Ce) single crystal and polycrystalline ceramic were investigated on their microstructural characteristics and luminescent and scintillating properties towards the identification of possible causes for the lower scintillation performance of the polycrystalline ceramic. Emphasis was placed on the thermoluminescence (TL) response. Radioluminescence results indicated a (11x) higher content of defects in the single crystal than in the polycrystalline ceramic. Lower optical transparency, higher self-absorption, and a higher degree of structural disorder localized in the grain boundaries of the polycrystalline ceramic were observed. TL results showed six glow peaks in the single crystal and four glow peaks in the polycrystalline ceramic within the 50–400 °C temperature range, all with first-order kinetics TL mechanism. Trap depths at similar peak temperatures were ~1.2–1.5 times deeper in the single crystal. In terms of scintillation response related to a Bi4Ge3O12 (BGO) crystal within the 31–662 keV gamma-ray energy range, the single crystal was about 2x brighter than the polycrystalline ceramic.