# Fileset

[Víllora_2024_Appl._Phys._Express_17_122007.pdf](https://mdr.nims.go.jp/filesets/01c33bd3-fbd4-4230-bae1-849fb1a6d93f/download)

## Creator

Encarnación G. Víllora, Makoto Saito, [Kiyoshi Shimamura](https://orcid.org/0000-0001-6502-8731)

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[High-quality 100% Ce<sup>3+</sup>:(Lu<sub>1−x</sub>Y<sub>x</sub>)<sub>2</sub>SiO<sub>5</sub> single crystals grown by the hydrothermal technique](https://mdr.nims.go.jp/datasets/89f86f3e-748c-4c7d-a5a9-160983fad766)

## Fulltext

High-quality 100% Ce3+:(Lu1−xYx)2SiO5 single crystals grown by the hydrothermal techniqueApplied PhysicsExpress      LETTER • OPEN ACCESSHigh-quality 100% Ce3+:(Lu1−xYx)2SiO5 singlecrystals grown by the hydrothermal techniqueTo cite this article: Encarnación G. Víllora et al 2024 Appl. Phys. Express 17 122007 View the article online for updates and enhancements.You may also likePositron emission mammography withtomographic acquisition using dual planardetectors: initial evaluationsMark F Smith, Raymond R Raylman, StanMajewski et al.-The growth of 122 and 11 iron-basedsuperconductor single crystals and theinfluence of dopingD P Chen and C T Lin-Quantitative PET in the 2020s: a roadmapSteven R Meikle, Vesna Sossi, EmilieRoncali et al.-This content was downloaded from IP address 144.213.253.16 on 24/12/2024 at 05:27https://doi.org/10.35848/1882-0786/ad9b6c/article/10.1088/0031-9155/49/11/022/article/10.1088/0031-9155/49/11/022/article/10.1088/0031-9155/49/11/022/article/10.1088/0953-2048/27/10/103002/article/10.1088/0953-2048/27/10/103002/article/10.1088/0953-2048/27/10/103002/article/10.1088/1361-6560/abd4f7https://pagead2.googlesyndication.com/pcs/click?xai=AKAOjssHI1Z8IoLtemSZ2FKSFDjtjBJFle0o53XpDy2_FpuIYRvg_qsFriGhW2ugyHzajDO8QtDps9Cflk4YINzAgqggfL6lG-KM64Ry2e-kKj3qX2OCJpgx3UE6XXQixQ8KwFjR-7W7LUDnVgcfEKdNYu23LDILSdbosU8TZnQy0bgFGy6rFY8K1JILy2H11RcSVXEdfpe7w1uR0BQWf8kGOSUVeF0FBztt9CKPdQjGTL41BATRP0VEZg8CEFzw-EMCmFo2n780P8_ZN-gXGhh8kBfl2YrDg8HnKcFjk9sNvd84xamOUB76-2ZkohmeudSBeC3_7Flh2Xcv3Ce4dYcKVEEBz1l-Mfj4enqBpo5ILPuR&sig=Cg0ArKJSzAcrRmqFtvH6&fbs_aeid=%5Bgw_fbsaeid%5D&adurl=https://ecs.confex.com/ecs/248/cfp.cgi%3Futm_source%3DIOP%26utm_medium%3Dbanner%26utm_campaign%3DIOP_248_abstract_submission%26utm_id%3DIOP%2B248%2BAbstract%2BSubmissionHigh-quality 100% Ce3+:(Lu1−xYx)2SiO5 single crystals grown by the hydrothermaltechniqueEncarnación G. Víllora1†*, Makoto Saito2, and Kiyoshi Shimamura1†*1National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan2Mitsubishi Chemical Corp., 1000 Kamoshida, Yokohama, Kanagawa, 227-8502, Japan*E-mail: VILLORA.Garcia@nims.go.jp and SHIMAMURA .Kiyoshi@nims.go.jp†These authors contributed equally to this work.Received November 29, 2024; revised December 5, 2024; accepted December 6, 2024; published online December 23, 2024The growth of Ce:(Lu1−xYx)2SiO5 single crystals by the hydrothermal technique is demonstrated. Crystallographic defects are suppressed thanksto the growth at much lower temperatures, and therefore, the complete incorporation of cerium in the Ce3+ valence state is obtained. The growthunder supercritical water lowers the temperature to less than half the melting point. In contrast, crystals grown from melt by the standardCzochralski technique possess intrinsic defects and undesirable Ce4+ ions as charge compensators. The growth of large-size single crystals withimproved scintillation properties at a low cost is envisaged. © 2024 The Author(s). Published on behalf of The Japan Society of Applied Physics byIOP Publishing LtdCe-doped lutetium oxyorthosilicate crystals, Lu2SiO5(LSO) and (Lu1−xYx)2SiO5 (x>0) (LYSO), areconsidered to be the best scintillators for gamma-raydetection in positron emission tomography (PET) of nuclearmedicine and in high-energy physics.1–8) They compromiserelevant properties: a high density (ρ ∼7 g cm−3) and aneffective atomic number (Zeff ∼66), resulting in a highstopping power (ρ ∙ Zeff4 ∼140× 106), a high light yield(LY) > 30,000 ph MeV−1, a short decay time (∼35 ns), and ahigh energy resolution (∼8% @ 662 nm). Commercializationof these crystals started in the late 1990s, and since then, largeefforts have been made to improve their performancefurther.9–20) Nowadays, mass production of 3- to 4-inchcrystals is carried out by the Czochralski (Cz) technique,despite the expensive Lu2O3 raw material and, more particu-larly, the ultra-high cost of Ir crucibles.The development of Ce:(Lu1−xYx)2SiO5 (x≥0) (Ce:L(Y)SO) single crystals has been closely bound from the beginningwith investigating the oxygen vacancies and the valence stateof Ce, and subsequent co-doping approaches. Soon, it wasfound that annealing under an oxidizing atmosphere improvesthe scintillation LY, shortens the decay time, and decreasesboth the afterglow and the thermoluminescence, suggestingthe presence of oxygen vacancies in as-grown crystals.21–24)While reducing the oxygen vacancy concentration, thisoxidation process promotes a partial Ce valence changefrom trivalent to tetravalent, as the absorbance spectraindicate.24,25) Therefore, a positive trade-off was assumedbetween less deep traps, causing non-radiative recombination,and a slight decrease in activator Ce3+ concentration. Ce4+cations have been considered undesirable because they lead toa broad charge transfer band (CTB) between oxygen 2p-orbitals of the valence band and Ce4+ 4f-orbitals within thebandgap (peaking at ∼4.9 eV) that does not contribute toluminescence in UV excitation spectra of Ce:L(Y)SO crystals.However, this is not always the case, as demonstrated forSr2CeO4 with Ce in the tetravalent state.26,27) Furthermore,Ce radioluminescence has been reported for 100%Ce4+-doped silica glasses28) and annealed Ce4+:Li6Y(B3O)3single crystals.29)By X-ray absorption near edge spectroscopy (XANES),the direct evidence of the Ce4+ presence has been pursuedin Ce:L(Y)SO24,25,30) as well as in Ce:Gd3Ga3Al2O12(Ce:GGAG)31,32) scintillators. Assuming a detection limitof 5%, the existence of Ce4+ in as-grown and annealed Ce:L(Y)SO crystals could not be found by XANES despiteobserving the CTB in absorbance spectra. Annealing candrastically increase the photo- and radioluminescence by40% and 20%, respectively, while the CTB slightlyenhances.24) In contrast, in the case of Ce:GGAG crystals, theCe4+ concentrations estimated by XANES differ from non-detectable to 50%.31,32)Beyond annealing, co-doping with divalent alkaline earthCa2+ and Mg2+ cations has been demonstrated to improvethe scintillation properties of Ce:L(Y)SO crystals signifi-cantly, even though it favors the incorporation of Ce in thetetravalent state.8,25,33–36) Ce4+ concentrations as high as20% for Ce,Mg:LYSO and 35% for Ce,Ca:LYSO have beenestimated by XANES upon small nominal codopantconcentrations.25) It is assumed that Ce4+ ions act as chargecompensators of intrinsic point defects, possibly the above-mentioned oxygen vacancies, so that original deep trapsthat lead to non-radiative recombination are suppressed.Furthermore, Ce4+ ions are suggested to contribute toradioluminescence in the same way as Ce3+ emitters upongamma excitation when they capture relaxing electrons fromthe upper conduction bands. Actually, prior to emission,Ce3+ centers are required to be excited while Ce4+ ones arenot. Instead, after emission, Ce4+ centers need to capture ahole while Ce3+ do not. Co-doping improves LY, decay time,and afterglow, but it has drawbacks such as spiral growth, thetendency of crystals to crack, uncontrolled doping, etc.,which lead to a low production yield.37) As a solution, tripleco-doping with divalent Zn2+ 15,38) and tetravalent Si4+ andZr4+ ions33) has been proposed.To summarize, though Ce3+ is the ideal isovalent activatorfor L(Y)SO on Lu3+ sites,39–41) non-isovalent Ce4+ ions arealways present since the CTB is systematically observed inCz-grown crystals. These ions are a part of the chargecompensators for intrinsic crystal defects, possibly oxygenContent from this work may be used under the terms of the Creative Commons Attribution 4.0 license. Any further distribution of thiswork must maintain attribution to the author(s) and the title of the work, journal citation and DOI.122007-1© 2024 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdApplied Physics Express 17, 122007 (2024) LETTERhttps://doi.org/10.35848/1882-0786/ad9b6chttps://crossmark.crossref.org/dialog/?doi=10.35848/1882-0786/ad9b6c&domain=pdf&date_stamp=2024-12-23mailto:VILLORA.Garcia@nims.go.jpmailto:SHIMAMURA .Kiyoshi@nims.go.jphttps://creativecommons.org/licenses/by/4.0/https://doi.org/10.35848/1882-0786/ad9b6cvacancies, that appear during the growth of oxides from meltat high temperatures. Though co-doping aids in suppressingnon-radiative recombination centers, improving the generalscintillation performance, it is not the ideal solution. Thegrowth of defect-free crystals with Ce in the trivalent state isdesirable. For this, a decrease in the growth temperatureseems to be a prerequisite. Flux growth is a promisingalternative to lower the growth temperature to avoid intrinsicdefects created at high temperatures. The solvothermal one,particularly the hydrothermal (HT) under supercritical water,is proper for the growth of oxide crystals with higher meltingpoints like Ce:L(Y)SO. As with quartz, large scaling coulddrastically reduce production costs while avoiding at thesame time the use of expensive Ir crucibles.In this study, we demonstrate the growth of undoped andCe-doped LSO and Ce:LYSO single crystals by the HTtechnique. The optical characterization of grown crystalsshows that the HT technique provides additional advantagesbeyond production costs, such as fewer crystal defects andfull incorporation of Ce in the desired trivalent state.Furthermore, though the direct measurement of Ce in thetetravalent state has been elusive, the way to discriminate thepresence of Ce4+ in low concentrations is elucidated.Undoped and Ce-doped LSO and LYSO single crystalswere grown with the HT technique using an autoclave.High-purity (4 N) Lu2O3, SiO2, Y2O3 and CeO2 were usedas raw materials. The nominal concentration of Y relativeto Lu was chosen as 10%, while the nominal concentrationof Ce-doped crystals was fixed at 0.15% relative to (Lu+Y). Potassium hydroxide (KOH) was used as a minera-lizer with a concentration in the water of approximately20 M. Relatively high growth temperatures, in the range630 °C to 730 °C, were needed to properly dissolve the rawmaterials in the supercritical fluid state. The reactor washeated for 12 hs, kept for 24 hs at the maximumtemperature, and then cooled, first for several hours at1 °C/h, then for 12 hs down to room temperature.Correspondingly, the used pressures were relatively high,typically ranging between 100 and 200 MPa. The reactionstook place within sealed Ag-ampoules of 10 mm in lengthand 5 mm in diameter under a temperature gradient ofabout 50 °C.To compare the new hydrothermal crystals with standardones, an undoped LSO crystal was grown by the Cz-technique with a 30 kW generator. 4 N raw materials ofLu2O3 and SiO2 (1 mol% enriched from the stoichiometricratio to compensate for evaporation losses) were mixed andloaded in an Ir crucible. A 1-inch single crystal was grownunder an Ar + 0.2% O2 flow of 1 l min−1. The rotation andpulling rates were 10 rpm and 1 mm h−1, respectively.Furthermore, to investigate the Ce incorporation from thevalence point of view a Ce:LYSO single crystal from Saint-Gobain was used for comparison.The crystals’ composition was measured by electron-probe-microanalysis (EPMA) using a JEOL JXA-8500Foperated at 15 kV. Powder X-ray diffraction (XRD) measure-ments were carried out using a Rigaku SmartLab3 diffract-ometer with Cu Kα radiation (1.54059Å). Transmittancespectra were recorded with a JASCO UV–vis-NIR spectro-meter V-570. Excitation and photoluminescence (PL) spectrawere acquired with a JASCO FP-8600DS fluorescencespectrometer.By spontaneous nucleation single crystals of few mm insize were obtained reproducibly by the HT technique.(a)(b)Fig. 1. (a) As-grown Ce3+:LSO & Ce3+:LYSO single crystals by the HT technique, and (b) 1-inch LSO single crystal grown by the Cz-technique.122007-2© 2024 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 17, 122007 (2024) E. G. Víllora et al.As-grown Ce:LSO and Ce:LYSO single crystals are shownin Fig. 1(a) as an example. Through the smooth and facetedsurfaces, it can be seen that the crystals are transparent,colorless, and without inclusions. On the contrary, the 1-inchundoped LSO single crystal grown by the Cz-techniqueexhibits a very rough surface, as can be seen in Fig. 1(b).Only after cutting and polishing, it could be confirmed thatthe crystal is transparent and colorless, free of cracks andinclusions from top to bottom.The composition of all crystals was evaluated by EPMA.The results are given in Table I. The measured concentrationsof Y and Ce in HT-grown crystals are very close to thenominal ones, suggesting that the segregation coefficients arevery close to one for both cations. Instead, the Y and Ceconcentrations in reference Ce:LYSO crystal grown bythe Cz-technique are lower by approximately 1/2 and 1/3,respectively. The content of other elements withinthe experimental error is comparable for both growthtechniques.The crystallographic phase of grown crystals was evalu-ated by powder XRD. All grown crystals exhibit themonoclinic phase with space group C12/c1. For example,the diffraction pattern of HT LSO is depicted in Fig. 2,together with the corresponding simulation. The differencebetween HT- and Cz-grown crystals becomes evident duringthe optical characterization in the ultraviolet UV wavelengthregion, first by comparing the undoped crystals, and then thedoped ones.The UV transmittance spectra of undoped LSO crystalsgrown by HT- and Cz-technique are shown in Fig. 3. Bothcrystals exhibit a high transparency above 250 nm. Below,towards the absorption cutoff, the Cz-grown crystal presentsan obvious, though shallow, broad absorption band. Theorigin of this band is assumed to be related to point defects,caused by growth at high temperatures (the melting point ofLSO is 2047 °C), when SiO2 evaporates strongly from themelt and some oxygen deficiency can be expected. On thecontrary, as the HT crystal was grown at a much lowertemperature, less than half, the formation of such intrinsicdefects could be entirely suppressed. Therefore, no opticallosses are observed in the whole transparent region. Thisadvantage of HT growth can be extrapolated to Ce-dopedcrystals, though it is not evident due to the overlap of Ceabsorption bands in the UV wavelength region.For doped crystals, the UV transmittance spectra of HT-grown Ce:LSO and Ce:LYSO are shown together with thespectrum of Cz-grown Ce:LYSO reference in Fig. 4(a). BothHT-grown crystals present four well-defined absorptionbands ascribed to the parity-allowed electric dipole 4f1 →5dj (j= 1–4) intraatomic Ce3+ transitions. The absorptionintensities are very close for both HT-grown crystals, in goodaccordance with the nominally equal Ce concentration. Incontrast, the Cz-grown Ce:LYSO crystal exhibits a lower 4f1→ 5d1 absorption, due to the lower Ce concentration as foundby EPMA, and not well-resolved higher energy absorptionbands. The absorption spectra were calculated using the well-known Bouguer–Lambert–Beer law and deconvoluted togain more insight. The absorption spectra of HT-growncrystals are described very well by the five Gaussian curves,as shown for the case of Ce:LSO in Fig. 4(b), with peakmaxima at 3.47, 3.80, 4.20, 4.69, and 5.90 eV (i.e. 357, 326,295, 264, and 210 nm), in good accordance with the reporteddeconvolution.42) This result suggests that all Ce is incorpo-rated as Ce3+ in HT crystals, and is further supported by thedeconvolution of Cz crystal in Fig. 4(c). Taking into accountthe relative intensities of Ce3+ absorption bands in HTcrystals, the absorption of Cz-grown Ce:LYSO is composedof the Ce3+ intraatomic absorption bands, with a 1/3 intensityof that of HT-grown Ce:LSO, in good agreement with EPMAresults, and a very broad absorption band starting at about3.5 eV (354 nm) and going beyond 6 eV, overlapping withthe conduction band. This absorption, with the maximum at∼4.9 eV, is generally attributed to the CTB of the Ce4+-O2-Table I. Relative cationic concentrations of single crystals measured byEPMA; recalculated to a total sum of three, like in the chemical formula.CationCZLSOCZCe:LYSOHTLSOHTCe:LSOHTLYSOHTCe:LYSOLu 1.920 1.820 1.903 1.921 1.729 1.744Si 1.080 1.098 1.097 1.076 1.100 1.095Y — 0.081 — — 0.171 0.158Ce — 0.001 — 0.002 — 0.003Fig. 2. Powder XRD pattern of HT-grown LSO single crystal comparedwith LSO simulation.Fig. 3. Transmittance of undoped HT- and Cz-grown LSO single crystalsin the UV wavelength region.122007-3© 2024 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 17, 122007 (2024) E. G. Víllora et al.centers. The location of the CTB varies with the host materialand is non-symmetric, consisting of at least three absorptionbands.27,43) Additionally, in contrast to Ce3+, the absorptioncross-section of the Ce4+ CTB is unknown in scintillatorcrystals. As the estimated absorption cross-section ratioCe4+/Ce3+ for Ce-doped glasses points out a significantdifference, ∼544) and ∼16,45) it is reasonable to assume thatthis ratio could be approximately one order of magnitudelarger in scintillators. This would explain why the presence ofCe4+ can be easily detected by transmittance measurementsin scintillator crystals with low Ce4+ concentrations, andobserving and quantifying Ce4+ in the XANES measure-ments, that are used as standard, is difficult. Furthermore, theinfluence of CTB absorption is also observed in the PLmeasurements.Figure 5 shows the excitation and emission PL spectra ofCe-doped crystals and the photograph of HT-grown Ce:LSOupon UV excitation. Both HT-grown crystals exhibit almostoverlapping curves due to similar Ce concentrations, as withthe transmittance curves of Fig. 4(a). The intensity ratios atthe wavelength maxima 354:294:264 are as high as1:0.84:0.61 and 1:0.77:0.60 for HT-grown Ce:LSO and Ce:LYSO, respectively, which contrasts with the low1:0.31:0.22 ratios in Cz-grown Ce:LYSO. The excitationspectra of HT crystals look like the absorption spectra,indicating that all the UV absorption occurs only on Ce3+ions. On the contrary, the excitation and absorption spectra ofthe Cz-grown Ce:LYSO crystal barely resemble each otherbelow 350 nm, where the CTB occurs. Photons absorbed atthe Ce4+-O2- centers do not contribute to PL emission, andtherefore, the 4f1 → 5dj (j= 2,3) excitation peaks are muchsmaller than the main 4f1 → 5d1 one. This phenomenon isobserved systematically in the reported PL spectra ofcommercial scintillators.3) Therefore, lower intensities inthe upper excitation bands can be used as an additionalsignature of the presence of undesirable Ce4+ ions. At last, itshould be noted that all crystals present approximately thesame emission spectra, except for the small differencescaused by Y mixing. The spectra are characterized by adouble peak broad emission from the lowest upper state tothe ground states of Ce3+, namely 5d1 → 4f1 (2F5/2 and2F7/2).The PL of HT-grown crystals upon UV excitation ishomogeneous and bright, as shown in the photograph ofFig. 5(b). Larger-sized crystals will be grown for the lightyield determination in the near future.The growth of undoped and Ce-doped LSO and LYSOcrystals by the HT technique is demonstrated. The advan-tages over the standard Cz-technique are, on the one hand,higher crystal perfection due to a much lower growthtemperature and, on the other hand, complete incorporationof Ce in the trivalent state Ce3+, thus paving the way for abreakthrough in scintillation performance. The elimination ofvarious defects is of crucial importance for the suppression ofnon-radiative recombination processes and, therefore, for the(a)(b) (c)Fig. 4. (a) Transmittance of Ce-doped single crystals: HT-grown Ce:LSO & Ce:LYSO and Cz-grown Ce:LYSO reference. Deconvolution of absorbancespectra of (b) HT-grown Ce:LSO and (c) Cz-grown Ce:LYSO single crystals.122007-4© 2024 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 17, 122007 (2024) E. G. Víllora et al.improvement of scintillation properties in terms of light yield,decay time, and afterglow. Currently applied co-dopingapproaches become superfluous, and instead, a revision ofthe optimal Ce concentration is necessary. Furthermore, asexpensive Ir crucibles are no longer needed and upscalingautoclaves for the growth of large-size single crystals isstraightforward, the production cost can be drasticallyreduced. Therefore, this study lets us envisage the develop-ment of Ce3+:LSO & Ce3+:LYSO single crystals with animproved scintillation performance at a much lower cost.1) C. W. E. van Eijk, Phys. Med. Biol. 47, R85 (2002).2) C. M. Pepin, P. Bérard, A-L. Perrot, C. Pépin, D. R. Lecomte, C. L. Melcher,and H. Dautet, IEEE Trans. Nucl. Sci. 51, 789 (2004).3) J. Chen, R. Mao, L. Zhang, and R-Y. Zhu, IEEE Trans. Nucl. Sci. 54, 718(2007).4) R-Y. Zhu, J. Phys. Conf. Ser. 587, 012055 (2015).5) R-Y. Zhu, J. Phys. Conf. Ser. 928, 012015 (2017).6) T. Yanagida, Proc. Jpn. Acad., Ser. B 94, 75 (2018).7) P. Lecoq et al., Phys. Med. Biol. 65, 21RM01 (2020).8) F. M. Addesa et al., JINST 17, P08028 (2022).9) M. Kapusta, M. Moszynski, M. Balcerzyk, J. Braziewicz, D. Wolski,J. Pawelke, and W. Klamra, IEEE Trans. Nucl. Sci. 47, 1341 (2000).10) A. Syntfeld-Każuch, M. Moszyński, Ł. Świderski, T. Szczęsńiak,A. Nassalski, C. L. Melcher, M. A. Spurrier, B. Goliszek, P. Kaminśki, andM. Nowaczyk, IEEE Trans. Nucl. Sci. 56, 2972 (2009).11) V. Jarý, M. Nikl, E. Mihóková, J. A. Mareš, P. Průša, P. Horodyský,W. Chewpraditkul, and A. Beitlerová, IEEE Trans. Nucl. Sci. 59, 2079(2012).12) N. G. Starzhinskiy, O. T. Sidletskiy, G. Tamulaitis, K. A. Katrunov, I.M. Zenya, Y. V. Malyukin, O. V. Viagin, A. A. Masalov, and I. A. Rybalko,IEEE Trans. Nucl. Sci. 60, 1427 (2013).13) V. Kalinnikov and E. Velicheva, Phys. Part. Nucl. Lett. 11, 259 (2014).14) F. Yang, R. Mao, L. Zhang, and R-Y. Zhu, Nucl. Instrum. Methods Phys.Res. A 784, 105 (2015).15) C. L. Melcher et al., JPS Conf. Proc. 11, 020001 (2016).16) E. Auffray et al., Phys. Status Solidi a 215, 1700798 (2018).17) Y. Wu, M. Tian, J. Peng, M. Koschan, I. Greeley, C. Foster, and C.L. Melcher, Phys. Status Solidi RRL 13, 1800472 (2019).18) G. Tamulaitis, E. Auffray, A. Gola, M. Korzhik, A. Mazzi, V. Mechinski,S. Nargelas, Y. Talochka, A. Vaitkevičius, and A. Vasil’ev, J. Phys. Chem.Solids 139, 109356 (2020).19) V. Kalinnikov, E. Velicheva, and Y. Uozumi, Phys. Part. Nucl. Lett. 18, 457(2021).20) V. Nadig, K. Herweg, M. M. C. Chou, J. W. C. Lin, E. Chin, C-A. Li,V. Schulz, and S. Gundacker, Phys. Med. Biol. 68, 075002 (2023).21) B. Chai, U.S. Patent U.S.A.7,166,845 (2007).22) B. Liu, Z. Qi, M. Gu, X. Liu, S. Huang, and C. Ni, J. Phys. Condens. Matter19, 436215 (2007).23) D. Ding, H. Feng, G. Ren, M. Nikl, L. Qin, S. Pan, and F. Yang, IEEETrans. Nucl. Sci. 57, 1272 (2010).24) S. Blahuta, A. Bessière, B. Viana, V. Ouspenski, E. Mattmann, J. Lejay, andD. Gourier, Materials 4, 1224 (2011).25) S. Blahuta, A. Bessière, B. Viana, P. Dorenbos, and V. Ouspenski, IEEETrans. Nucl. Sci. 60, 3134 (2013).26) L. Van Pieterson, S. Soverna, and A. Meijerink, J. Electrochem. Soc. 147,4688 (2000).27) L. Li, S. Zhou, and S. Zhang, Chem. Phys. Lett. 453, 283(2008).28) M. Fasoli, A. Vedda, A. Lauria, F. Moretti, E. Rizzelli, N. Chiodini,F. Meinardi, and M. Nikl, J. Non-Cryst. Solids 355, 1140(2009).29) D. Yuan, E. G. Víllora, N. Kawaguchi, D. Nakauchi, T. Kato, T. Yanagida,and K. Shimamura, Jpn. J. Appl. Phys. 62, 010614 (2023).30) C. L. Melcher, S. Friedrich, S. P. Cramer, M. A. Spurrier, P. Szupryczynski,and R. Nutt, IEEE Trans. Nucl. Sci. 52, 1809 (2005).31) G. Dantelle, G. Boulon, Y. Guyot, D. Testemale, M. Guzik, S. Kurosawa,K. Kamada, and A. Yoshikawa, Phys. Status Solidi b 257, 1900510(2020).32) Y. Wu, F. Meng, Q. Li, M. Koschan, and C. L. Melcher, Phys. Rev. Appl. 2,044009 (2014).33) Y. D. Zavartsev, S. A. Koutovoi, and A. I. Zagumennyi, J. Cryst. Growth275, e2167 (2005).34) M. A. Spurrier, P. Szupryczynski, K. Yang, A. A. Carey, and C. L. Melcher,IEEE Trans. Nucl. Sci. 55, 1178 (2008).35) K. Yang, C. L. Melcher, P. D. Rack, and L. A. Eriksson, IEEE Trans. Nucl.Sci. 56, 2960 (2009).36) W. Chewpraditkul, C. Wanarak, T. Szczesniak, M. Moszynski, V. Jary,A. Beitlerova, and M. Nikl, Opt. Mater. 35, 1679 (2013).37) S. Blahuta, K. Yang, V. Ouspenski, and P. Menge, Poster presented at IEEENucl. Sci. Symp. & Med. Imaging Conf. (Strasbourg, France), Oct. 29 -Nov. 5, 2016.38) M. A. Spurrier, P. Szupryczynski, H. Rothfuss, K. Yang, A. A. Carey, andC. L. Melcher, J. Cryst. Growth 310, 2110 (2008).39) H. Suzuki, T. A. Tombrello, L. Melcher, and J. S. Schweitzer, IEEE Trans.Nucl. Sci. 40, 380 (1993).40) L. Pidol, O. Guillot-Noël, A. Kahn-Harari, B. Viana, D. Palenc, andD. Gourier, J. Phys. Chem. Solids 67, 643 (2006).41) D. W. Cooke, B. L. Bennett, K. J. McClellan, J. M. Roper, and M.T. Whittaker, Phys. Rev. B 61, 11973 (2000).42) V. A. Tedzhetov, A. V. Podkopaev, and A. A. Sysoev, IOP Conf. Series:Mater. Sci. Eng. 525, 012044 (2019).43) A. M. Efimov, A. I. Ignat’ev, N. V. Nikonorov, and E. S. Postnikov, Opt.Spectrosc. 111, 426 (2011), Original Russian text published in Optika iSpektroskopiya 458.44) M-L. Brandily-Anne, J. Lumeau, L. Glebova, and L. B. Glebov, J. Non-Cryst. Solids 356, 2337 (2010).45) A. M. Efimov, A. I. Ignatiev, N. V. Nikonorov, and E. S. Postnikov, J. Non-Cryst. Solids 361, 26 (2013).(a) (b)Fig. 5. (a) Normalized excitation and emission PL spectra of Ce-doped crystals: HT-grown Ce:LSO & Ce:LYSO and Cz-grown Ce:LYSO reference. (b)Photograph of the HT-grown Ce:LSO crystals upon 365 nm lamp excitation.122007-5© 2024 The Author(s). Published on behalf ofThe Japan Society of Applied Physics by IOP Publishing LtdAppl. Phys. Express 17, 122007 (2024) E. G. Víllora et al.https://doi.org/10.1088/0031-9155/47/8/201https://doi.org/10.1109/TNS.2004.829781https://doi.org/10.1109/TNS.2007.897823https://doi.org/10.1109/TNS.2007.897823https://doi.org/10.1088/1742-6596/587/1/012055https://doi.org/10.1088/1742-6596/928/1/012015https://doi.org/10.2183/pjab.94.007https://doi.org/10.1088/1361-6560/ab9500https://doi.org/10.1088/1748-0221/17/08/P08028https://doi.org/10.1109/23.872975https://doi.org/10.1109/TNS.2009.2028235https://doi.org/10.1109/TNS.2012.2190940https://doi.org/10.1109/TNS.2012.2190940https://doi.org/10.1109/TNS.2013.2244910https://doi.org/10.1134/S154747711403011Xhttps://doi.org/10.1016/j.nima.2014.11.103https://doi.org/10.1016/j.nima.2014.11.103https://doi.org/10.7566/JPSCP.11.020001https://doi.org/10.1002/pssa.201700798https://doi.org/10.1002/pssr.201800472https://doi.org/10.1016/j.jpcs.2020.109356https://doi.org/10.1016/j.jpcs.2020.109356https://doi.org/10.1134/S1547477121040105https://doi.org/10.1134/S1547477121040105https://doi.org/10.1088/1361-6560/acbde4https://doi.org/10.1088/0953-8984/19/43/436215https://doi.org/10.1088/0953-8984/19/43/436215https://doi.org/10.1109/TNS.2009.2036351https://doi.org/10.1109/TNS.2009.2036351https://doi.org/10.3390/ma4071224https://doi.org/10.1109/TNS.2013.2269700https://doi.org/10.1109/TNS.2013.2269700https://doi.org/10.1149/1.1394124https://doi.org/10.1149/1.1394124https://doi.org/10.1016/j.cplett.2008.01.033https://doi.org/10.1016/j.cplett.2008.01.033https://doi.org/10.1016/j.jnoncrysol.2009.01.043https://doi.org/10.1016/j.jnoncrysol.2009.01.043https://doi.org/10.35848/1347-4065/aca3e5https://doi.org/10.1109/TNS.2005.856594https://doi.org/10.1002/pssb.201900510https://doi.org/10.1002/pssb.201900510https://doi.org/10.1103/PhysRevApplied.2.044009https://doi.org/10.1103/PhysRevApplied.2.044009https://doi.org/10.1016/j.jcrysgro.2004.11.290https://doi.org/10.1016/j.jcrysgro.2004.11.290https://doi.org/10.1109/TNS.2007.913486https://doi.org/10.1109/TNS.2009.2027018https://doi.org/10.1109/TNS.2009.2027018https://doi.org/10.1016/j.optmat.2013.04.024https://doi.org/10.1016/j.jcrysgro.2007.10.075https://doi.org/10.1109/23.256584https://doi.org/10.1109/23.256584https://doi.org/10.1016/j.jpcs.2005.10.175https://doi.org/10.1103/PhysRevB.61.11973https://doi.org/10.1088/1757-899X/525/1/012044https://doi.org/10.1088/1757-899X/525/1/012044https://doi.org/10.1134/S0030400X11090050https://doi.org/10.1134/S0030400X11090050https://doi.org/10.1134/S0030400X11090050https://doi.org/10.1016/j.jnoncrysol.2010.02.020https://doi.org/10.1016/j.jnoncrysol.2010.02.020https://doi.org/10.1016/j.jnoncrysol.2012.10.024https://doi.org/10.1016/j.jnoncrysol.2012.10.024