Defect Engineering in Ce-Doped Aluminum Garnet Single Crystal Scintillators

Abstract

Mg-codoped Lu 3 Al 5 O 12 :Ce single crystal scintillators were prepared by a micropulling down method in a wide concentration range from 0 to 3000 ppm of Mg codopant. Their structure and chemical composition were checked by X-ray diffraction and electron probe microanalysis techniques. Absorption and luminescence spectra, photoluminescence decays, and thermoluminescence glow curves were measured together with several other scintillation characteristics, namely, the scintillation decay, light yield, afterglow, and radiation damage to reveal the effect of Mg codoping. Several material characteristics manifest a beneficial effect of Mg codopant. We propose a model explaining the mechanism of material improvement which is based on the stabilization of a part of the cerium dopant in the tetravalent charge state. The stable Ce 4+ center provides an additional fast radiative recombination pathway in the scintillation mechanism and efficiently competes with electron traps in garnet scintillators.

Towards Bright and Fast Lu3Al5O12:Ce,Mg Optical Ceramics Scintillators

“…For LuAG:Ce,Mg single crystals, a maximum LY of 23100 photo ns/MeV was observed already at very low Mg 2+ concentrations (100 ppm, 30 times lower than the 0.3% Mg in our ceramics). [ 30 ] A LY decrease for high Ca 2+ concentrations (0.1-0.4% in the melt) has also been reported in LYSO:Ce,Ca single crystals, [ 42,43 ] but the real concentration of the Ca co-dopant in this kind of crystals was measured as low as 60 ppm. [ 25 ] Even though our ceramics are more heavily doped, we expect that only a small fraction of the Mg ions diffuses into the grains and infl uences the scintillation, whereas the majority acts mostly as sintering aids between the grains.…”

“…[ 28,29 ] The presence of the Ce 4+ charge transfer (CT) absorption peaking at about 240 nm, which increases with increasing Mg concentration, also adds to the absorption band below 300 nm, similarly to what has been observed for LuAG:Ce,Mg and Gd 3 Al 2 Ga 3 O 12 :Ce,Mg (GGAG:Ce,Mg) single crystals. [ 30,31 ] Before annealing, this additional CT absorption band is only observable for the highest Mg concentration (0.6%). It becomes much stronger after the air-annealing process as it can be observed for all the LuAG:Ce,Mg ceramics in most of which absorption saturation occurs (Figure 1 b).…”

A study of radiation effects on LuAG:Ce(Pr) co-activated with Ca

“…Composition engineering to achieve these goals is the major aspect of many present studies. Unlike the previously applied methods aiming suppression of existing electron traps [14][15][16], it is suggested that the new trap centers (Ce 4 þ ) that could be created upon co-doping with divalent impurities [22,23] may efficiently compete in electron capture with Yb 3 þ and thus compensate its negative role, if present in noticeable amounts in raw materials. After proving on the first samples that there is no damage to scintillation performance, single crystals with Ce and Ca varied in a wide range of concentrations were grown.…”

Effect of thermal annealing on scintillation properties of Ce:Gd2Y1Ga2.7Al2.3O12 under different atmosphere

“…Three peaks as in [27] and Ca 2? co-doped LuAG:Ce [28] and LYSO:Ce [29]. Here we can also find the increasing intensity of broadband absorption 200-350 nm after air-annealing, and the band can be attributed to the Ce -O 2-charge transfer(CT) absorption band in our experiment does not show the same features with that given in the literature, it may be due to that the samples co-doped with divalent ions lead to more amount of stable Ce 4? , thus more stronger absorption around 260 nm in the Ca 2? , Mg 2? , B 2?…”