Enhancement of Scintillation Properties of LYSO:Ce Crystals by Al Codoping

Single-crystal lutetium yttrium oxyorthosilicate doped by cerium (LYSO:Ce) has been widely adopted as a scintillator material for radiation detection. The demands from nuclear medical imaging, as well as high-energy physics, are calling for ever-increasing scintillation properties. Here, Al3+ codoping of LYSO:Ce is realized for the first time, and a series of LYSO:Ce,xAl (x = 0, 0.3, 0.6, and 1.0 atom %) crystals are successfully grown by a micro-pulling down (mu-PD) method. It is found that at x = 0.6 atom %, the overall scintillation properties are simultaneously improved. In particular, the slow component of rise time and the afterglow level are drastically reduced by 350% (from 304 to 86 ps) and an order of magnitude (from 0.2 to 0.02%), respectively. The energy resolution is also enhanced from 16.1 to 10.9%. These results are attributed to the fact that Al3+ codoping significantly reduces the concentration of traps, accelerates the excited state lifetime of Ce3+ ions and introduces a faster scintillating luminescence center, Ce4+ ions. Our LYSO:Ce,0.6 atom % Al crystal offers a gain in the image signal-to-noise ratio of 1.4 over the non-codoped crystal, which will significantly benefit the next-generation time-of-flight positron emission tomography and enable more precise diagnosis of diseases.