Ce-Doped Lutetium Pyrosilicate Scintillators LPS and LYPS

In this paper we present scintillation, optical, and thermoluminescence properties of recently discovered scintillation material, LPS (Lu₂Si₂O₇:Ce) and composition with yttrium LYPS ((Lu,Y)₂Si₂O₇ :Ce). The latter was first grown at Siemens Medical Solutions Molecular Imaging, and had an yttrium concentration of 50%. Both have the thorveitite structure, with monoclinic symmetry, space group C2/m. XRD measurements confirmed the expected crystal structure in which there is a single crystallographic site for lutetium or yttrium ions, with six oxygen neighbors. The trivalent cerium activator ions are assumed to occupy the cation lattice site. The excited 5d state of Ce³⁺ is split into 2 observable levels with luminescence emission occurring only from the lowest 5d level to the 4f ground state with a Stokes shift of ~2250 cm^-1. In this paper, we report on the scintillation properties of LPS and LYPS crystals. The difference in scintillation properties observed between samples is discussed. It was based on thermoluminescence data obtained in the temperature range from 30 to 600 K. These data show that the analyzed samples have surprisingly different sets of traps. Crystal growth and cutting issues of LPS and LYPS are also briefly discussed