Towards Bright and Fast Lu3Al5O12:Ce,Mg Optical Ceramics Scintillators

The recent advent of Lu3Al5O12:Ce optical ceramics marks a turning point in scintillator material technology. Because of their lower preparation temperature, brightness, and robustness such materials can now compete with single crystals. Their further scintillation efficiency optimization includes the thorough control of the defects responsible for optical and scintillation losses. The choice of sintering agent appears critical to achieve both high optical transparency and scintillation performance. In this work, the optical investigations coupled with X-ray absorption near-edge spectroscopy evidence the beneficial role of MgO sintering agent. Mg2+ co-dopants in ceramics drive the partial conversion of Ce3+ to Ce4+. The Ce4+ center, however, does not impair the scintillation performance due to its capability to positively influence the scintillation process. The importance of simultaneous application of such co-doping and annealing treatment is also demonstrated. With 0.3 at% Mg, our ceramics display a light yield of approximate to 25000 photons/MeV with short 1 mu s shaping time, a relative fast component intensity as high as 60%, and very low afterglow. Such performances are better than those of the isostructural single crystals ever reported. We discuss the role of co-doping and annealing in the scintillation mechanism that make such combined treatments a positive strategy for material engineering.