Nanostructured Ceramic LSO Scintillators Using Dynamic Powder Compaction

The understanding of matter and the nuclear forces that govern their structure has led to scientific revelations which have had not only great impact on the physics community, but also on technological breakthroughs leading to advancements in nuclear medicine, homeland security, and materials research. Currently, there is a definitive need for advancements in detector technology for the next generation of accelerator facilities, such as the Facility for Rare Isotope Beams (FRIB) at Michigan State University. Bright, fast, scintillator materials such as Lu2SiO5 (LSO) are typically used in single crystal form, whose growth methods are time consuming, expensive, and the degree of dopant homogeneity can be limited. For single crystal applications such as laser gain media and more recently scintillator materials, current research is examining the use of conventional ceramic processing techniques instead of crystal growth. Ceramic processing is significantly lower cost, can make a wider variety of shapes, and is also capable of higher dopant levels and improved dopant homogeneity. However for non-cubic systems such as monoclinic LSO, it has proven difficult to achieve the same transparency as a single crystal due to the birefringence of the monoclinic system. In this situation, the optical scattering that reduces transparency is even more sensitive to processing history (e.g. porosity and microstructure) than a cubic system. Using its experience in transparent magnesium aluminate spinel (MgAl2O4) for laser and sensor applications and development of polycrystalline lutetium aluminum garnet (LuAG) for scintillator applications, TA & amp;T will improve the optical and scintillation characteristics of monoclinic LSO by addressing the main causes for poor transparency in a non-cubic system: residual porosity, inclusions, and grain size. TA & amp;T will utilize optimized powder processing techniques, novel compaction methods, and specialized sintering profiles to improve the optical and scintillation properties of polycrystalline LSO to levels equivalent or superior to that of single crystal LSO. Development of a novel, inexpensive method to produce transparent polycrystalline LSO will have a long term and significant market impact on nuclear medicine applications, such as Positron Emission Tomography (PET) scan and single photo emission computer tomography (SPECT). Furthermore, the techniques developed for dynamically compacting LSO into a green body that is suitable for sintering to a transparent state will have benefits in other industries that use or are developing nanopowder processes, such as transparent armor for military applications, polycrystalline laser gain materials, and high strength structural materials