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A series of (CexGd1–x)3Ga2Al3O12 (x = 0–0.8%) (Ce/GGAG) crystals were grown by the optical floating zone (OFZ) method. Ce/GGAG single crystals with good crystallinity were successfully obtained by ...

This work aims to fully analyze the luminescence spectra and time response properties of LYSO:Ce (Lu2-2xY2xSiO5:Ce) scintillation crystals with different Y contents. The photoluminescence excitation (PLE) and emission (PL) spectra of Ce1 and Ce2 luminescence centers in LYSO:Ce crystals with different Y contents have been systematically examined. The shape of photoluminescence emission spectra and the contribution of the energy transfer process between Ce1 and Ce2 have been varied with the yttrium content in the crystal. Based on the photoluminescence and scintillation decay time measurements, a table has been shown to provide the relationship between the decay time and Y content in the crystal. Meanwhile, the afterglow measurements demonstrate the relationship between long-lived delay recombination processes and the free carrier traps existing in the bandgap, and the source of afterglow has been analyzed.

Gigahertz hard X-ray imaging presents an unprecedented challenge to both timing and spatial resolutions for inorganic scintillator-based front imagers. A beam test with 30-keV X-rays from the Advanced Photon Source (APS) showed that 5-mm BaF2 plates resolve well 30-keV X-ray septuplets of 27-ps width and 2.83-ns spacing. Pixelated crystal screens with a pitch down to $400~\mu \text{m}$ were fabricated by mechanic slicing for BaF2, BaF2:Y, and LYSO crystals. Their spatial resolution and detection efficiency for hard X-rays are defined by the pitch and thickness, respectively. Thicker monolithic crystal screens show poorer spatial resolution, which may be improved using a small optical aperture with a loss in both efficiency and dynamic range for hard X-rays. Future plans include pursuing smaller crystal pitches by laser slicing and research and development on novel ultrafast inorganic scintillators.

A systematical exploration of energy transfer processes in Lu2(1–x)Y2xSiO5:Ce (LYSO) crystals under vacuum ultraviolet – ultraviolet (VUV–UV) excitation was implemented. The relationship between energy transfer and scintillation properties was established. It is revealed that there are mainly three energy transfer types in the crystal i.e. host → Ce1/Ce2/STEs, Ce1 → Ce2 and STEs → Ce1/Ce2. The influence of Y content of the LYSO crystals on the energy transfer efficiency of the above processes was carefully analyzed. Besides, we find a special component of the crystal i.e. Y content = 45 at% at which the energy resolution and light output of the crystal perform the worst.

The influence of lanthanum content on thermally stimulated luminescence properties of La2xLu2(1−x)SiO5:Ce (x = 0, 0.08, 0.18 and 1.50 at.%) crystals was investigated. Trapping parameters such as electron trap depth Et and electron traps content n0 were fitted with general order kinetic function. According to the results of the VUV transmittance spectra and band gap calculation which based on the density functional theory with the generalized gradient approximation of Perdew–Burke–Ernzerhof (GGA–PBE), band structure of the crystals and recombination mechanisms of released electrons were further studied. Results showed that there were mainly two kinds of electron traps, namely shallow (Et ≈ 0.2 eV) and deep (Et ≈ 1.0 eV) traps. With the increasing of La content, the concentration of deep traps was obviously depressed, and the depth of deep traps decreased at the same time, which was explained by suggesting the downward shift of the bottom of conduction band.

In this article, we report the local heating effects induced by laser irradiation in mechanically exfoliated WS2 monolayers and the characterization of the resulting inhomogeneous temperature field with the technique of photoluminescence spectroscopy. By comparatively measuring the PL spectra of the monolayer WS2 in different contact conditions as well as in air and vacuum, we confirm the existence of remarkable heating in the monolayer due to laser irradiation. In particular, it is found that a specific excitonic emission peak could be used to characterize the inhomogeneous Gaussian-like thermal field and the heat transfer behaviors. Based on the dependence of the excitonic emission energy on temperature, the local temperature induced by laser irradiation may be obtained, i.e., a local temperature up to 213 °C was found at the central region of the irradiated area in vacuum for the excitation power of 450 μW. Such optical method may be applied to the measurement of local heating effects in 2D semiconductors and relevant van der Waals devices.

The phoswich detectors can determine the location of nuclear interactions with the matrix and it is an effective approach to improve the spatial resolution at the edge of the field of view in positron emission tomography. In this study, we proposed a kind of bilayer structure garnet ceramic scintillators for phoswich detectors. Bilayer Pr:LuAG/Ce:LuAG ceramic scintillations with different thickness ratio were fabricated through solid-state reaction and vacuum sintering without further cutting or stacking process. The phase, microstructure, fluorescence and scintillation properties were characterized and studied. The decay time of the Pr:LuAG layer was about 21.8 ns while that of the Ce:LuAG layer was 58.6 ns. Different 5d-4f emission bands of 290–450 and 475-700 nm were observed in the Pr:LuAG layer and Ce:LuAG layer, respectively. These two features meet the basic requirements of phoswich detectors. Separation of interactions with γ-ray in different layers has achieved in the pulse height spectra. These properties reveal that this kind of mutilayer structure garnet ceramic scintillators have potential application value in the field of phoswich detectors. This article is protected by copyright. All rights reserved.

This paper presents a detailed study of the influence of yttrium (Y) concentration on thermally stimulated luminescence (TSL) of LYSO:Ce crystals and establishes the relationship between electron traps and scintillation properties. With the increase of Y concentration, the glow curve shifts toward higher temperatures and the trap depth increases gradually. Our results revealed two groups of electron traps with one shallow (Et ≈ 0.10-0.26 eV) and one deep (Et ≈ 1.00-1.21 eV). Our TSL results suggest that the amount of shallow traps varied with Y content has a positive correlation with energy resolution, while the amount of deep traps is inversely proportional to light output. In order to analyze the variation trend of trap depths and their mechanism in detail, we calculated the band gap with the PBE functional and VUV excitation spectra. The results show that the increase of band gap possibly leads to the increase of deep electron trap depth.

This work investigates the intrinsic radioactivity of Lu 2(1−x) Y 2x SiO5 :Ce (LYSO:Ce) crystals grown by Czochralski method (Cz) with various yttrium (shortened as Y) contents (x= 0-100 at.%). Energy spectra of the crystals excited with 137Cs and the intrinsic radioactivity related to 176Lu atoms as a function of Y content were investigated. It is illustrated that the intrinsic radioactivity depends on the content of Y, which also affects the energy spectrum and energy resolution of LYSO crystal. Results show that energy resolution of LYSO:Ce crystals can be improved by subtracting background spectra from the energy spectra. The experiment result also confirms the size effect of intrinsic radioactivity in LYSO:Ce crystal. For the LYSO crystal in large size, the influence of intrinsic radioactivity on the energy spectrum cannot be ignored, while it can be weakened by background subtracting.

Multicomponent garnets, due to their excellent light yield and energy resolution, become one of the most promising scintillators used for homeland security and nuclear non-proliferation applications. This work focuses on the optimization of Ce-doped (Gd,Y) 3 (Ga,Al) 5 O 12 scintillators using a combination strategy of pre-screening and scale-up. Ce-doped Gd x Y 1− x Ga y Al 5− y O 12 ( x =1, 2 and y =2, 2.2, 2.5, 2.7, 3) polycrystalline powders were prepared by high-temperature solid state reaction method. The desired garnet phase in all the samples was confirmed using X-ray diffraction measurement. By comparing the radioluminescence intensity, the highest scintillation efficiency was achieved at a component of Gd 2 Y 1 Ga 2.7 Al 2.3 O 12 :Ce powders. A (Gd 2 Y 1 )Ga 2.7 Al 2.3 O 12 doped with 1% Ce single crystal with dimensions of O35×40 mm was grown by Czochralski method using a oriented seed. Luminescence and scintillation properties were measured. An optical transmittance of 84% was achieved in the concerned wavelength from 500 to 800 nm. Its 5d–4f emission of Ce 3+ is at 530 nm. The light yield of a Ce1%: Gd 2 Y 1 Ga 2.7 Al 2.3 O 12 single crystal slab at a size of 5×5×1 mm 3 can reach about 65,000±3000 Ph/MeV along with two decay components of 94 and 615 ns under 137 Cs source irradiation.

Lu2O3:Eu scintillation film is one of the most attractive candidate for the hard X-ray imaging, especially for sub-micrometer spatial resolution X-ray detectors. This study was focused on the preparation and characterization of Lu2O3:Eu structured scintillation film on (0 0 1) sapphire substrate by laser chemical vapor deposition (LCVD). The grazing incidence X-ray diffraction (GIXRD) measurement shows that the film with thicknesses of 3 μm is oriented along the (4 1 1) direction. The morphology and luminescent properties, including photoluminescence excitation (PLE), photoluminescence (PL) and PL decay, were measured and discussed. The sub-micrometer spatial resolution was obtained at BL13W1 station at Shanghai synchrotron radiation facility (SSRF).

Indium doped cesium iodide (CsI:In) single crystals were grown by the Bridgman method. A comparison study of the scintillation properties of our CsI:In and commercially available CsI:Tl single crystals was carried out, including scintillation decay time, energy resolution, non-proportionality, absolute light yield, and afterglow. Under X-ray excitation, the CsI:In emission corresponds to a symmetrical broad band centered at 545 nm. Its scintillation decay time is $1.99 \pm 0.02~\mu\hbox{s}$ at room temperature under $^{137}{\rm Cs}\gamma $ -ray excitation. The CsI:In light yield was found to be $34,700 \pm 1735$ photons per MeV with an energy resolution of $9.1 \pm 0.3\% $ , based on the pulse height spectra under $^{137}{\rm Cs}$ excitation. The afterglow level of CsI:In over 130 ms after pulsed X-ray excitation was two orders of magnitude higher than that of CsI:Tl.

Cerium-doped 1% Ce:Gd2Y1Ga2.7Al2.3O12(GYGAG) single crystal samples grown via Czochralski method were annealed under air, O2 and N2 atmospheres from 350 to 1400 °C. The X-ray excited luminescence spectra, energy spectra and UV as well as thermally stimulated luminescence (TSL) spectra were performed comparatively on “as-grown” and thermally annealed samples. It was found that the luminescence efficiency after annealing in air and O2 was significantly enhanced compared to the non-annealed samples and this phenomenon was suggested to be caused by the existence of some oxygen vacancies in the Ce:GYGAG crystals. And the oxygen vacancies in the as-grown GYGAG crystals can be effectively eliminated by means of annealing in O2 containing atmosphere without changing the luminescence mechanism. From the TSL curves before and after annealing, three traps within 77–650 K were found to be related to oxygen vacancies.

CsI:Tl scintillators were hindered from computer tomography and high-speed imaging applications by a serious afterglow problem. In this study, the effects of ultralow-concentration Sm codoping on the scintillation characteristics of CsI:Tl were investigated. Pulsed X-ray excited afterglow after 50 ms in 0.005 mol% Sm-codoped CsI:Tl was lowered by over one order of magnitude in comparison with Sm-free one. The beneficial effects of ultralow-concentration Sm codoping also appeared to be maintaining the light yield and energy resolution. The light yield and energy resolution after 0.005 mol% Sm codoping were 71,700 ± 6000 photons/MeV and 6.9% at 662 keV, respectively.

CsI:Tl single crystals with different Bi3+ concentrations from zero to 0.05 mol% were grown by the vertical Bridgman technique. The effects of Bi3+ codoping on the scintillation properties of CsI:Tl single crystals were investigated, including afterglow level, relative light yield, energy resolution, scintillation decay time and radioluminescence spectra. Afterglow suppression by Bi3+ codoping was confirmed, but it resulted in a considerable decrease of light yield and energy resolution. The deterioration of light yield was ascribed to the self-absorption effect induced by Bi3+ ions. The physical mechanism and role of Bi3+ ions in afterglow suppression were proposed.

In this paper, Cerium-doped lutetium yttrium oxyorthosilicate crystal (Lu,Y)2SiO5:Ce (LYSO:Ce) samples were used to thoroughly investigate the structural and optical anisotropy of the crystal. Results presented demonstrate that there is insignificant anisotropy in most of the properties of LYSO:Ce crystal – structural integrity, refractive index, transmittance, excitation and emission spectra, and photoluminescence decay time, which is a comparative advantage for various applications including preparation of optical ceramics. Besides, anisotropy phenomena in fine-structure of LYSO:Ce, afterglow, thermoluminescence and light output of samples with small size were observed. A mechanism of anisotropy in defect distribution is discussed.

Single-crystal X-ray diffraction (SCD), X-ray fluorescence (XRF), inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray excited luminescence (XEL) measurements were performed to investigate structure details and segregation coefficients of (Lu 1− x Y x ) 2 SiO 5 :Ce ( x =0 at%, 8.7 at%, 25.7 at%, 44.7 at%, 65.7 at%, 87.9 at% and 100 at%). Y 3+ cations were found to have a preferential occupation for RE 1 site (7-oxygen-coordinated) over RE 2 site (6-oxygen-coordinated), which results in a greater increase of cell parameter c than that of a with increase in Y content due to LYSO's microstructure characteristics. Results presented here revealed that the less the difference in electronegativity and effective ionic radius between the two ions, the easier substitution of one ion by the other, and hence the higher segregation coefficients. Besides, the contribution of luminescence of Ce1 and Ce2 in the whole XEL was evaluated, and the location of Ce 3+ ion was discussed.

Both Zr-codoped Lu_(0.8)Sc_(0.2)BO_3:Ce polycrystalline powders and single crystals were obtained by solid-state reaction and Czochralski method, respectively. The effects of Zr codoping on the optical absorption, Ce^(3+)/Ce^(4+) ratio, scintillation efficiency, decay time and point defect in Lu_(0.8)Sc_(0.2)BO_3:Ce materials were examined systematically. Our results show that there is no positive contribution of Zr^(4+) ion codoping to the scintillation efficiency. And the reasons for the deterioration of scintillation efficiency by codoping Zr^(4+) were revealed.

Single crystal of Lu2Si2O7 (LPS):0.5%Ce,0.1%Ca was grown by the Czochralski method. The X-ray excited luminescence (XEL), photoluminescence excitation (PLE), photoluminescence (PL) and transmittance spectra were measured and discussed. The as grown LPS:Ce,Ca sample presents excellent optical quality with 81% transmittance. Two absorption peaks locate at 300 and 350 nm, corresponding to the electron transition of Ce3+ from 4f ground to 5d1 and 5d2 respectively. According to the Gaussian fitting, the XEL curve of LPS:Ce,Ca can be fitted into two peaks centering at 378 and 407 nm respectively. It is found that the addition of Ca2+ in LPS:Ce introduces more oxygen vacancies, leading to the decreases of the luminescence efficiency of LPS:Ce. Through the thermally stimulated luminescence (TSL) measurement, two kinds of charge trap are found in LPS:Ce,Ca, whose energy depths are 1.20 and 1.47 eV. The trap at 1.20 eV is intrinsic electron trap induced by Ce3+ doping in LPS host and the other trap is formed by the both impact of and defects.

In this paper, monovalent cation Li 1+ co-doped Lu 0.79− x Sc 0.2 Ce 0.01 Li x BO 3 ( x = 0, 0.005, 0.01, 0.03, 0.05) polycrystal samples were prepared and a series of methods (such as X-ray excited luminescence, diffuse reflectance, fluorescence decay, X-ray Absorption Near Edge Structure (XANES), thermoluminescence, photoluminescence emission and excitation spectra) was used to comprehensively investigate its co-doping effects. It was found that Li co-doping may play a negative role: introducing more point defects and additional color centers (such as Ce 4+ and oxygen vacancy). Furthermore, the increase in the number of traps in the vicinity of luminescence center Ce 3+ ions will induce the competition absorption of excitation energy with the luminescence centers, and hence deteriorate the luminescence properties.

The Lu0.8Sc0.2BO3 polycrystalline powders doped with 1 at%Ce3+ and co-doped with Ca2+, Mg2+, or Sr2+ with varying concentration were fabricated by conventional solid-state reaction method. We applied X-ray diffraction, optical diffuse reflectance spectrum, luminescent spectra under UV and X-ray excitation, fluorescence decay time and X-ray absorption near edge spectroscopy to study the effects of divalent ions co-doping on the Lu0.8Sc0.2BO3:Ce scintillation materials. Through experiments, the influence of divalent ions co-doping strategy on scintillation efficiency and the action mechanism were revealed.

To improve particle detectors in physics research and PET scanners in medicine, for example, better scintillators are sought. In this study, researchers succeed in creating a ceramic that is free of defect-induced host luminescence. In a combined ``defect engineering'' and ``band-gap engineering'' approach, the detrimental influence of lattice defects is significantly reduced, by simultaneously lowering the concentration of point defects and shifting their energy levels. Thanks to this approach, efficient scintillator material with high density, high light yield, and short decay time is obtained.

The calcite phase of LuBO_3 and ScBO_3 polycrystalline powders were synthesized by solid state reaction method, and the Lu_(1−x)Sc_xBO_3:Ce (x=0.2, 0.5, 0.7) single crystals were grown by the Czochralski method. A large composition deviation between the initial polycrystalline powders and final single crystal was confirmed by electron probe micro-analysis. Raman spectroscopy revealed that moderate lattice disorder was induced by scandium substitution. However, based on the single crystal X-ray study, we finally concluded that the crystal structure of lutetium scandium orthoborate still crystallized in the rhombohedral system belonging to R3^- c. Furthermore, the relationship between the energies of the five 5d levels of Ce^(3+) and the crystalline environment was revealed. The total redshift, total crystal field splitting, and centroid shift of Lu_(1−x)Sc_xBO_3:Ce^(3+) were calculated based on their VUV excitation spectra. The variations trend of these observed spectroscopic parameters was in accordance with the predicted ones.

Cerium doped lutetium scandium orthoborate Ce3+:Lu0.8Sc0.2BO3 is a novel and promising inorganic scintillator. For the sake of better understanding its scintillation mechanism, several approaches were undertaken to locate the Ce3+ energy levels relative to the host. To estimate the energy position of Ce3+4f levels with respect to the valence band, X-ray photoelectron spectroscopy (XPS) was used. Furthermore, the photoluminescence decays as a function of temperature, a widely used technique, was utilized to find the relative positions of Ce3+5d levels to the conduction band. Finally, the Ce3+ energy levels in Lu0.8Sc0.2BO3 host was constructed, meanwhile, the effectiveness of the XPS technique to estimate the energy position of Ce3+ 4f levels relative to the conduction band was evaluated.

The optical absorption, temperature dependence of emission spectra, prompt nanosecond decays and millisecond delayed recombination decays for Pr^(3+) center in Lu_(0.8)Sc_(0.2)BO_3 host were studied. The photoluminescence decay time decreases from 16 ns (80 K) to 11 ns (300 K), but its steady-state emission intensity at 300 K is stronger than that at 80 K and towards higher temperatures is further decreasing comparatively much less with respect to the decay time shortening, which was proved to be associated with the thermal ionization processes occurring from 5d_1 relaxed state of Pr^(3+). The quantitative parameters governing the ionization processes were calculated.

The air-annealing effects on Lu0.8Sc0.2BO3:Pr3+ crystals grown by Czochralski method (Cz-method) were studied at different temperatures. Its scintillation efficiency reached optimum of about 500% of BGO after annealing at 1000 °C due to the removal of the oxygen vacancies. However, after annealing at a higher temperature, it was found that its scintillation efficiency was evidently reduced, because of oxidization of praseodymium ions. Through experiments, results show for Pr3+-doped Lu0.8Sc0.2BO3 scintillator, air-annealing plays either positive or negative role, depending on annealing temperature: low temperature annealing is favorable for the removal of oxygen vacancies, but annealing at high temperature causes oxidation of Pr from trivalent to tetravalent state, which are demonstrated by H2 annealing experiment.

Lu 0.8 Sc 0.2 BO 3 crystals doped with 1 at%Ce 3+ and co-doped 0.1 at% and 0.5 at%Pr 3+ were grown by the Czochralski method. The concentrations of Pr 3+ and Ce 3+ in crystals were measured by the ICP-AES method. Absorption spectra, VUV–UV spectra, fluorescence decay time and X-ray excitation luminescence spectra were investigated at room temperature. The excitation luminescence spectra of Ce 3+ emission and decay curves from the lower excited state levels of the 4f 1 5d 1 and 5d 1 electronic configurations of the Pr 3+ and Ce 3+ conspicuously indicated the non-radiative energy transfer from Pr 3+ to Ce 3+ . The detailed pathways were shown in the energy level diagram of the respective Ce 3+ and Pr 3+ in Lu 0.8 Sc 0.2 BO 3 host. In addition, the scintillation efficiency data indicated that the energy transfer effect is directly associated with the Pr 3+ concentration.

Transparent Lu 0.8 Sc 0.2 BO 3 crystals doped with 1 at%Ce 3+ and co-doped with 1 at% and 3 at%Ga 3+ were grown by the Czochralski method. We applied absorption spectrum, luminescence spectra under UV and X-ray excitation, fluorescence decay curve, three dimensional thermoluminescene and X-ray absorption near edge spectroscopy to study the effect of Ga 3+ co-doping on the Lu 0.8 Sc 0.2 BO 3 :Ce scintillation crystals. Experimental results indicated that no positive contribution of the Ga 3+ ion doping on the scintillation efficiency was found. The causes for the deterioration of scintillation efficiency by co-doping Ga 3+ were revealed. The decrease of practical cerium content and the Ce 3+ /Ce 4+ ratio in crystals, and the increase of the trap concentrations, although the corresponding trap types still maintained the same, played a joint influence on the degrading of scintillation efficiency of Lu 0.8 Sc 0.2 BO 3 :Ce crystals.

Temperature-dependence of Raman spectroscopy on LuBO 3 structure was performed in order to obtain information on structural changes induced by temperature evolution. The stability of the calcite phase and low-temperature vaterite phase of LuBO 3 were both evaluated. For the sample with low-temperature vaterite phase, a strong first-order phase transition occurred during 1000–1200 °C, as indicated by the behavior of the Raman modes: the Raman bands split and new bands appear. The transition was associated with the B–O bond being broken in the cyclic B 3 O 9 groups at high temperature, forming an open B 3 O 9 group consisting of BO 4 and BO 3 . Moreover, the influence of In 3+ content on the structural characteristics of LuBO 3 was investigated. It was found that the calcite phase of LuBO 3 can be stabilized up to 1550 °C at least when the n (In)/ n (Lu + In) ratio was more than 20 at%. The crystal growth and characterizations of Lu 1− x In x BO 3 :Ce materials deserve further investigation.

Emission and excitation spectra of undoped and Ln(3+) (Ln = Ce, Pr, Nd, Yb)-doped Lu(0.8)Sc(0.2)BO(3) were studied by vacuum ultraviolet spectroscopy, and the X-ray excited luminescence spectra were measured as well at room temperature. The undoped specimen presented two different emissions upon excitation at energies in the vicinity of the band gap or with X-ray. The emission at the highest energy side, located at 4.77 eV, was ascribed to self-trapped exciton, which is anchored by electron capture around the Sc site. We also observed three broad emission bands at 4.43, 3.02, and 2.10 eV, which might be attributed to the trapped exciton, defect -related emissions, or both. Energy transfer processes to the doped lanthanide ions in Lu(0.8)Sc(0.2)BO(3) via exciton state or sequential electron-hole capture are discussed. Finally, the energy level diagram for divalent and trivalent lanthanides in Lu(0.8)Sc(0.2)BO(3) was constructed using the obtained spectroscopic parameters and the three parameters method (Dorenbos, P. J. Phys.: Condens. Matter 2003, 15, 8417).

Transparent Lu 0.8 Sc 0.2 BO 3 :Ce single crystals doped with different Ce concentrations were grown by the Czochralski method. X-ray diffraction measurements showed that the as-grown crystals all possessed hexagonal structure with R 3 ¯ c space group. The more initial Ce ion doping content in Lu 0.8 Sc 0.2 BO 3 :Ce, the smaller effective segregation coefficient of Ce in crystal will be, confirmed by the inductively coupled plasma atomic emission spectrometry (ICP-AES) tests. The Ce 3+ 5d → 4f emission band and five excitation states were both observed in the photoluminescence spectra (PL). The increase of luminescence center in crystal or the concentration quenching exerts effects in the change of PL decay time, depending on the cerium concentration. The radioluminescence spectra showed that the Lu 0.8 Sc 0.2 BO 3 :Ce crystals had one broad emission band corresponding to the 5d → 4f transition of Ce 3+ ions, similar to their PL spectra. Consequently, we found that Lu 0.8 Sc 0.2 BO 3 :2 at.%Ce crystal achieved the maximum scintillation efficiency and for Lu 0.8 Sc 0.2 BO 3 :3 at.%Ce crystal, there might be already affected by a concentration quenching effect.

Lu 0.8 Sc 0.2 BO 3 :RE 3+ (RE = Eu, Tb) polycrystalline powders were prepared by high temperature solid state reaction method. The X-ray diffraction measurements confirmed that the doped materials were all monophasic solid solution powders. The influences of activator ion (Eu 3+ or Tb 3+ ) concentration on the photoluminescence and radioluminescence characteristics were investigated and discussed. The Tb 3+ doped materials showed excellent light yields than Eu 3+ doped materials under X-ray excitation. The fluorescence decay times of the optimal materials excited by UV were measured. Their defect properties were studied by thermoluminescence (TL) as a function of temperature (300–600 K) and the corresponding trap depth, frequency factor and detrapping time were theoretically calculated. The Eu 3+ and Tb 3+ ions were the unique recombination centers in corresponding samples. In addition, considering their attracting luminescence properties and excellent physical properties (high-density and non-hygroscope), the Lu 0.8 Sc 0.2 BO 3 :RE 3+ (RE = Eu, Tb) can be used for X-ray medical imaging system, hence their crystal growth and characterizations deserve further investigation.

Transparent Pr3+-doped Lu0.8Sc0.2BO3 crystal has been grown by Czochralski method. The crystal structure is confirmed to be hexagonal with space group R 3 ¯ c checked by XRD measurement. The optical transmission spectra (absorption spectra), photoluminescence emission and excitation spectra, fluorescence decay time and the X-ray excited luminescence spectra of the crystal are measured at room temperature. The cut-off edge of this material locates at round 250 nm and there is a broad absorption in the region from 250–500 nm. The photoluminescence emission spectrum is dominated by fast 5d4f1 → 4f2 band peaking at 303 nm having 11.9 ns decay time. The measurement results show that the Pr3+-doped Lu0.8Sc0.2BO3 crystal, due to high density, fast decay time, high scintillation efficiency and non-hygroscopic property, could be a promising scintillator.

Cerium-doped lutetium scandium orthoborate single crystals as potential scintillation materials were grown by the floating zone (FZ) method for the first time and the Czochralski (Cz) grown crystal was used for comparison. In this paper, the representative composition Lu0.5Sc0.5BO3:0.5at%Ce (abbreviated as LSBO:Ce) was selected as the research target. The phase structure of FZ-grown LSBO:Ce crystal was characterized by X-ray diffraction and its optical properties were investigated using photoluminescence emission (PL), excitation (PLE), radioluminescence (RL) spectra. The defect properties of LSBO:Ce crystals were studied by thermoluminescence (TL) as a function of temperature (300–600 K). The glow curve of FZ-grown LSBO:Ce crystal shows three TSL peaks, at 350, 400, 552 K, corresponding to a trap depth of 0.99, 1.14 and 1.50 eV, respectively. Based on UV-irradiation TL measurements and air-annealing experiments, the former two kinds of traps could be ascribed to the radiation-induced defects and the third kind originated from the oxygen vacancies formed during crystal growth. These defects also existed in the Cz-grown LSBO:Ce crystal.

Cerium-doped lutetium orthoborate LuBO3 : Ce crystal is a promising scintillator with excellent properties, but the single crystal is difficult to grow because of the phase transition. In this article, the reported high-temperature (HT) vaterite phase was proved to exist at a low temperature (below 1200°C). Moreover, the real HT phase of LuBO3 was identified for the first time. The observed HT phase structure of LuBO3 was isostructural with the hexagonal structure of YbBO3 with space group P6322(182). The temperature dependence of the lattice constant and unit cell of the above phase structures were also investigated. The relative stability of calcite phase of LuBO3 could associate with fitness of the radius of Lu3+ ion for the six-coordination structure.

The crystals of (Lu 1− x Ce x ) 2 Si 2 O 7 (LPS) ( x = 0.003, 0.005, 0.0075, 0.01 and 0.013) are grown by Czochralski (Cz) method. The scintillation and optical properties of these LPS:Ce crystals were studied and compared systematically, mainly focused on the absorption, photoluminescence (PL) and photoluminescence excitation (PLE) and decay time. It is found that the self absorption of LPS:Ce is increased as the cerium doping concentration increases; the PLE curves of LPS:Ce samples are influenced by the both cerium doping concentrations and sample thickness. Specially, thicker and higher cerium doped LPS:Ce, i.e. the stronger self absorption, will lead to incomplete PLE curves. The temperature dependence of luminescence of LPS:0.3%Ce, including the decay time, PLE and PL properties, is investigated.

Solid solution crystals of Lu 1− x Sc x BO 3 :Ce 3+ ( x = 0.2, 0.3, 0.5, 0.7) were grown by Czochralski method. These crystals have high optical transmittance within wavelength concerned, except for an absorption shoulder in Lu 0.8 Sc 0.2 BO 3 :1at%Ce 3+ crystal from 360 to 530 nm. With the increase of Sc/Lu ratio, the excitation and emission spectra have redshift due to change of Ce 3+ crystalline environment and the lifetime gradually increases due to the increase of emission wavelength. Efficient energy transfer from the self-trapped excitons to Ce 3+ ions was observed. Lu 0.8 Sc 0.2 BO 3 :1at%Ce 3+ crystal, due to high density, short decay time, high scintillation efficiency and non-hygroscopic property, could be a promising scintillator.

The dependence of structural characteristics of cerium-doped lutetium scandium orthoborate (Lu1−xScx)BO3:Ce solid solutions on Sc/Lu ratio was investigated. It was found that the calcite phase of LuBO3 can be stabilized up to 1550 °C at least when the n(Sc)/n(Lu + Sc) ratio was ≥10 at.%. The closed correlations between Sc3+ or Ce3+ molar ratio in the host and luminescence mechanism were discussed in detail. Based on the requirements of steady phase structure, better luminescence efficiency and higher density, the reasonable n(Sc)/n(Lu + Sc) and n(Ce)/n(RE) ratio should be in the range of 30–50 at.% and 0.3–0.5 at.%, respectively. A modified composition, (Lu0.5Sc0.5)0.995Ce0.005BO3 solid solution, was selected to grow single crystal. Its X-ray excited luminescence intensity can be as high as about 27% of LYSO:Ce standard crystal and the effective lifetime is round 20.1 ns. Hence, the cerium-doped lutetium scandium orthoborate crystal is a promising scintillator for X-ray detection or γ-ray detection.

Single crystals of Lu1-xScxBO3:Ce (x=0.2, 0.3, 0.5, 0.7) were grown by Czochralski method. Continuous solid solution with calcite structure and a linear compositional dependency of crystal lattice parameter in the system Lu1-xScxBO3:Ce are formed and their symmetry belong to hexagonal system with R3c space group checked by X-ray powder diffraction. The electron probe micro-analysis measurements show that the main inclusions in Lu1-xScxBO3:Ce crystals are in the form of Sc rich oxide and Ce rich oxide. The ICP-AES tests show that the more Sc ion content in Lu1-xScxBO3:Ce, the smaller effective segregation coefficient of Ce in crystal will be. The X-ray excited luminescence spectra of Lu1-xScxBO3:Ce crystals all present a double peaked emission band with maxima round 370 and 400 nm corresponding to Ce3+ emission and a self trapped excitons (STE) band peaking at 269 nm. In addition, due to high density, high relative light yield, fast decay time and no-hygroscopic property, Lu0.8Sc0.2BO3:1 at%Ce crystal could be a good candidate material for scintillation application by improving the crystal quality and cerium concentration. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

A new double borate Li 6 Lu(BO 3 ) 3 :Ce crystal with dimensions up to Φ 35×21 mm 3 was prepared by the Czochralski method. The X-ray diffraction pattern of the crystal was measured. The melting point and solidifying point of the Li 6 Lu(BO 3 ) 3 :Ce crystal were measured by DSC. Its luminescence properties at room temperature were investigated by ultraviolet fluorescence spectrometer and X-ray stimulated luminescence (XSL) spectrometer. According to these dates, we consider that the Li 6 Lu(BO 3 ) 3 :Ce crystal is a promising scintillator.