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, Al 3+ 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 (μ-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 Al 3+ codoping significantly reduces the concentration of traps, accelerates the excited state lifetime of Ce 3+ ions and introduces a faster scintillating luminescence center, Ce 4+ 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.

Gd3Al2Ga3O12:Ce (GAGG:Ce) shows potential application in the next-generation positron emission tomography material due to its high light yield and excellent energy resolution. The main method currently available to accelerate the scintillation decay time of GAGG:Ce is mainly through the codoping of low valence ions such as Mg2+, which partially converts Ce3+ to Ce4+ through a charge compensation mechanism. However, there is no clear and reasonable explanation for the deterioration of light yield by codoping with Mg2+ in GAGG:Ce. Therefore, further study of the Mg2+ codoping GAGG:Ce crystal is of great importance for improving the scintillation properties of GAGG:Ce. In this study, two sets of GAGG crystal samples containing different Ce concentrations without or with 0.5 atom % of Mg2+ ion codoping were grown by the micropulling down method. The optimal Ce concentration decreases after Mg2+ codoping, whereas the light yield degenerates significantly. This novel phenomenon suggests that the reduction of light yield after Mg2+ codoping is not only due to the reduction of the luminescence center but also the formation of {Ce3+–Mg2+} and {Ce4+–Mg2+} associates affects the luminescence emission. This work can provide a novel and significant view for high-performance codoped GAGG:Ce component design and performance modification.

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