In radiation detection systems employing scintillation crystals for the detection of high-energy particles such as x-rays or neutrons, the scintillator often limits the performance of the system. Ideally, a scintillator should have a high light yield for good energy and position resolution, a fast response time for good time resolution and high density and atomic number Z for efficient x-ray detection. The latter property is of less importance in the case of (thermal) neutron detection. Obviously, there are many other criteria such as transparancy of the material to its own emission, ease of crystal growth, etc. However, there is no commercially available material that meets all these criteria and the choice for a particular scintillator is often a compromise among these and other factors.