Evidence and Consequences of Ce$^{4+}$ in LYSO:Ce,Ca and LYSO:Ce,Mg Single Crystals for Medical Imaging Applications

Blahuta, Samuel; Bessière, Aurélie; Viana, Bruno; Dorenbos, P.; Ouspenski, V.

doi:10.1109/tns.2013.2269700

Cited by 211 publications

(191 citation statements)

References 28 publications

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“…Increase of absorption in the UV, as compared to crystals with no co-doping, was earlier observed in YAG:Ce,Ca [22], GGAG:Ce,Ca [24], LuAG:Ce,Mg [23,25], LYSO:Ce,Ca(Mg) [26], LuAP:Ce,Ca [30]. The charge compensation in garnets following incorporation of divalent co-dopants is creation of oxygen vacancies [20,21]; in Cedoped crystals they may favor formation of Ce 4 þ states for charge compensation [22,23,26]. Conversion of all Ce 3 þ to Ce 4 þ in asgrown YAG:Ce,Ca (evidenced by absence of 4f-5d absorption of Ce 3 þ ) and reconversion of some part of Ce 4 þ to Ce 3 þ upon reducing heat treatment was reported in Ref.…”

Section: Luag:cementioning

confidence: 61%

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

Պետրոսյան

Ovanesyan

Derdzyan

et al. 2015

Journal of Crystal Growth

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Section: Luag:cementioning

confidence: 61%

“…[23][24][25][26] and references therein). The present studies therefore address directly the radiation tolerance of these newly developed materials.…”

Section: Introductionmentioning

confidence: 99%

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

Պետրոսյան

Ovanesyan

Derdzyan

et al. 2015

Journal of Crystal Growth

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“…[ 21 ] Similarly to what occurs in the other materials mentioned above, [ 24 ] Figure 1 shows the absorption spectra of both as-sintered and air-annealed LuAG:Ce,Mg ceramics. The absorption bands at about 447 and 347 nm are related to the Ce 3+ 4f →5d 1 and 5d 2 transitions, respectively.…”

Section: Introductionmentioning

confidence: 76%

“…A similar trend was also observed in Me 2+ (Me = Mg, Ca) co-doped LSO single crystals and Lu 0.8 Sc 0.2 BO 3 :Ce polycrystalline powders. [ 24,32 ] By using a linear combination fi t method, proportions of the Ce 3+ and Ce 4+ contributions in the spectra have been estimated. The fi tted results are reported in Table 1 .…”

Section: Full Paper Full Paper Full Papermentioning

confidence: 99%

“…[ 22,23 ] The presence of Ce 4+ centers in the LSO:Ce 3+ ,Me 2+ structure due to local charge compensation following Me 2+ co-doping was clearly be identifi ed by its charge transfer (CT) absorption located in the UV and considered responsible for the improved scintillation performance displayed by the material. [ 24,25 ] Participation of Ce 4+ in the scintillation process was suggested to occur also in sol-gel silica glasses. [ 26,27 ] In this case the presence of Ce 4+ is related to the oxidizing atmosphere during the glass synthesis rather than to a co-doping effect.…”

Section: Introductionmentioning

confidence: 99%

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

Liu

Mareš

Feng

et al. 2016

Advanced Optical Materials

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needed. Within the last two decades, a number of excellent scintillators based on Ce 3+ and Pr 3+ -doped materials, together with truly novel nanoscintillators, nanocomposites, and phase-separated material systems, have been discovered and studied in depth. [1][2][3][4][5][6][7][8] This high R&D activity in the scintillator fi eld was triggered by the pressing needs of modern medical imaging and radiotherapy, of high-energy physics, homeland security, and environmental applications. Among them, Cedoped Lu 3 Al 5 O 12 (LuAG:Ce) aluminum garnets have attracted much attention because of their relatively high density of 6.73 g cm −3 , 5d -4f electric dipole allowed radiative transition of Ce 3+ with emission at around 500-550 nm, fast scintillation response of about 60 ns, and high theoretical light yield (LY) value of 60000 photons/MeV. [ 9,10 ] It was found that LuAG:Ce single crystal containing 0.55 at% Ce 3+ ions prepared by Bridgman technique is a highly competitive scintillator displaying a LY of about 26000 photons/MeV with a shaping time of 1.5 μs, close to that of Lu 2 SiO 5 :Ce (LSO:Ce). [ 11 ] Based on the understanding of defect chemistry, an effective bandgap engineering approach was successfully applied to the LuAG system. Multicomponent garnets, featuring a balanced admixture of Gd and Ga cations in the Lubased garnet structure, form a new family of materials with an amazingly high light yield up to 58000 photons/MeV, a value exceeding that of the best Lu 2-x Y x SiO 5 :Ce (LYSO:Ce) materials by about 40%. [12][13][14][15] Therefore, oxides based on garnet structure are presently considered as competitive candidates for advanced scintillation applications.However, the low segregation coeffi cient of Ce 3+ ions in the LuAG lattice is detrimental for the growth of homogeneously doped large LuAG:Ce single crystals, especially for high Ce 3+ concentrations (Ce 3+ > 0.2 at%). [ 16 ] It was also noticed that Lu Al antisite defects (AD) can severely deteriorate the scintillation characteristics of LuAG:Ce single crystals by acting as shallow traps, thus delaying the energy transport to the Ce 3+ emission centers. [ 17 ] Therefore, extensive research has recently been aimed at the preparation of ceramic analogues, which are characterized by lower preparation temperatures, more uniform doping, and lower cost. One point to consider is that during The choice of sintering agent appears critical to achieve both high optical transparency and scintillation performance. In this work, the optical investigations coupled with X-ray absorption near-edge spectroscopy evidence the benefi cial role of MgO sintering agent. Mg 2+ co-dopants in ceramics drive the partial conversion of Ce 3+ to Ce 4+ . The Ce 4+ center, however, does not impair the scintillation performance due to its capability to positively infl uence the scintillation process. The importance of simultaneous application of such co-doping and annealing treatment is also demonstrated. With 0.3 at% Mg, our ceramics display a light yield of ≈25000 photons/MeV wit...

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