Processing of Transparent Polycrystalline AlON:Ce3+ Scintillators

A new polycrystalline ceramic scintillator is reported for potential use in radiation detection and medical imaging applications. The goal was to develop cerium-activated aluminum oxynitride (AlON:Ce3+) ceramics, which can be produced using ceramic processes in comparison to the high-cost, low-yield single-crystal growth technique. A phase pure AlON:Ce3+ powder with cubic symmetry was successfully synthesized at high temperature under a reducing atmosphere to convert Ce4+ to Ce3+ in the solid solution. Two different activator concentrations (0.5 and 1.0 mol%) were explored. Fully dense and transparent AlON:Ce3+ ceramics were produced by a liquid-phase-assisted pressureless sintering. The crystal field splitting around the Ce3+ activator in the AlON was comparable to the splitting induced by Br- and the Cl- ligands, which produced an emission spectrum perfectly matching the maximum quantum efficiency range of the photomultiplier tube for radiation detection. Both optical excitation and radiation ionizations in AlON:Ce3+ were demonstrated. Challenges and mechanisms related to the radioluminescence efficiency are discussed.