Development of novel polycrystalline ceramic scintillators

For several decades most of the efforts to develop new scintillator materials have concentrated on high-light-yield inorganic single-crystals while polycrystalline ceramic scintillators, since their inception in the early 1980's, have received relatively little attention. Nevertheless, transparent ceramics offer a promising approach to the fabrication of relatively inexpensive scintillators via a simple mechanical compaction and annealing process that eliminates single-crystal growth. Until recently, commonly accepted concepts restricted the polycrystalline ceramic approach to materials exhibiting a cubic crystal structure. Here, we report our results on the development of two novel ceramic scintillators based on the non-cubic crystalline materials: Lu ₂SiO₅:Ce (LSO:Ce) and LaBr₃:Ce. While no evidence for texturing has been found in their ceramic microstructures, our LSO: Ce ceramics exhibit a surprisingly high level of transparency/translucency and very good scintillation characteristics. The LSO:Ce ceramic scintillation reaches a light yield level of about 86% of that of a good LSO:Ce single crystal, and its decay time is even faster than in single crystals. Research on LaBr₃ :Ce shows that translucent ceramics of the high-light-yield rare-earth halides can also be synthesized. Our LaBr₃ : Ce ceramics have light yields above 42000 photons/MeV (i.e., >70% of the single-crystal light yield).