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

Abstract

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.

Slow Emission Suppression in YSO:Ce Scintillation Crystals by Cr Codoping

“…However, the variation of scintillation decay time is not monotonically increasing, and after high concentration doping, it also shows a decreasing trend. This is mainly attributed to the fact that scintillation decay time is not only influenced by shallow energy levels , but also by the Ce1/Ce2 ratio , and the lifetimes of excited states of Ce1 and Ce2 …”

“…Light output and scintillation decay time are important parameters for evaluating scintillation performance. ,,− Gamma spectroscopy is a commonly used method for characterizing crystal light output and energy resolution. ,, Figure a shows the gamma spectra of YSO:Ce, x Cr crystals with different Cr 4+ concentrations under 137 Cs radiation source irradiation. Figure b–g shows the scintillation decay time of crystals.…”

“…The crystal scintillation decay signal is collected using an oscilloscope (Agilent DSO 9404A) and a PMT (Hamamatsu R6233) with a working voltage of −1400 V during testing. More testing details can be found in ref . The thermoluminescence (TL) curve was collected by using the Ocean Optics QE65000 spectrometer.…”

“…In the early research, the optimization of orthosilicate scintillation crystals was often achieved by codoping different kinds of ions, such as Ca 2+ , Mg 2+ , Cu 2+ , Li + , and Al 3+ , into the system. ,− By adjusting the concentration of shallow level traps in the crystal, , the charge valence state of the luminescence center ions, ,, making Ce tend to occupy the fast emitting Ce1 site, , or shortening the excited state lifetime of Ce, the decay time of the crystal was shortened. However, some studies have also focused on accelerating the scintillation kinetics by codoping other luminescent centers with Ce-doped crystals.…”

Ce3+-Doped Li2Ca5Gd(BO3)5 Phosphors with Multiple Luminescent Centers and High Pressure Sensitivity under Near UV Excitation

“…Ce 3+ -based luminescent materials have attracted a lot of attention due to their applications in white light emitting diodes (WLEDs), , scintillators, , afterglow materials, , and laser crystals. , Ce 3+ with the [Xe]­4 f 1 electron configuration usually exhibits a dual-band emission characteristic because the ground state is split into 2 F 5/2 and 2 F 7/2 due to the spin–orbital interaction, and such a 5 d –4 f transition of Ce 3+ is always efficient due to the spin- and parity-allowed characteristics, leading to a strong photoluminescent (PL) emission . Besides, the 5 d energy level of Ce 3+ is sensitive to the surrounding crystal field strength (CFS), while the 4 f energy level is well shielded by the outer 5 s and 5 p orbitals; as a consequence, the 5 d –4 f transition can vary from ultraviolet (UV) to orange-red light depending on the CFS in different hosts. − For instance, Ba 2 GaB 4 O 9 Cl:Ce 3+ exhibits two emission bands at 324 and 347 nm and Y 3– x Mg 2 AlSi 2 O 12 : x Ce 3+ emits an orange-red light centered at ∼600 nm. , …”