Influence of K+ on the crystal structure, defect, and scintillation performances of LYSO:Ce crystals

Lu1.8Y0.2SiO5:Ce (LYSO:Ce) crystals have become the material of choice for the current application of commercial TOF-PETs due to their high light output, short decay time, and fast rise time. In this study, a series of K+ co-doped LYSO:Ce crystals were prepared by the μ-PD method, in which the K+ concentrations were 0, 0.2 atom %, 0.6 atom %, and 1.0 atom %, respectively. It was found that the scintillation performances were simultaneously optimized when the K+ concentration was 0.6 atom %. Compared to the sample of LYSO:Ce, LYSO:Ce, 0.6 atom % K showed an approximately 12.6% increase in light yield, a shortening of the fastest scintillation decay time to 38.3 ns, and a 1.4-fold decrease in afterglow level. Moreover, the K+ could replace the Lu3+ site but could not cause the transition of Ce3+ to Ce4+. Meanwhile, the connection between optical and luminescence performances and K+ concentration was discussed. The luminescence contribution of Ce2 became stronger with the K+ concentration increased. Furthermore, the research on K+ co-doping of LYSO:Ce crystals could offer better knowledge and be informative for the selection of future co-dopants.