Scintillation properties of LYSO crystals

We evaluate the scintillator properties of LYSO (Lu_(2-x)Y_xSiO₅:Ce) crystals with the amount of lutetium ranging from 15 to 100%. The radii of the cations Lu³⁺ and Y³⁺ differ by only 5%, therefore, one can substitute yttrium for lutetium without changing the structure. The addition of yttrium has several advantages: the raw material Y₂O₃ is much cheaper than Lu₂O₃ and the melting point is up to 100°C less. Since yttrium has a much lower atomic number and atomic mass than lutetium, LYSO crystals have a lower density and effective atomic number. This means that LYSO does not absorb X-rays as well as LSO. LYSO with 50% lutetium, however, has an effective atomic number that is just 11% less than LSO and the light yield of LYSO with 30% or more lutetium is roughly the same as that of LSO samples. LYSO scintillators with 50% or more lutetium could provide a more cost effective scintillator material for some applications.