Transparent Garnet Ceramic Scintillators for Gamma-ray Detection

Lanthanide gallium/aluminum-based garnets have a great potential as host structures for scintillation materials for medical imaging. Particularly attractive features are their high density, chemical radiation stability and more importantly, their cubic structure and isotropic optical properties, which allow them to be fabricated into fully transparent, high-performance polycrystalline optical ceramics. Lutetium/gadolinium aluminum/gallium garnets (described by formulas ((Gd,Lu)(3)(Al,Ga)(5)O-12:Ce, Gd-3(Al,Ga)(5)O-12:Ce and Lu3Al5O12:Pr)) feature high effective atomic number and good scintillation properties, which make them particularly attractive for Positron Emission Tomography (PET) and other gamma-ray detection applications. The ceramic processing route offers an attractive alternative to single crystal growth for obtaining scintillator materials at relatively low temperatures and at a reasonable cost, with flexibility in dimension control as well as activator concentration adjustment. In this study, optically transparent polycrystalline ceramics mentioned above were prepared by the sintering-HIP approach, employing nano-sized starting powders. The properties and microstructures of the ceramics were controlled by varying the processing parameters during consolidation. Single-phase, high-density, transparent specimens were obtained after sintering followed by a pressure-assisted densification process, i.e. hot-isostatic-pressing. The transparent ceramics displayed high contact and distance transparency as well as high light yield as high as 60,000-65,000 ph/MeV under gamma-ray excitation, which is about 2 times that of a LSO:Ce single crystal. The excellent scintillation and optical properties make these materials promising candidates for medical imaging and.-ray detection applications.