記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：Journal of Physics Conference Series  

Single crystals of Y<inf>3</inf>(Ga,Al)<inf>5</inf>O<inf>12</inf>:Ce(YAGG:Ce) co-doped with various Mg were grown by the micro-pulling-down method, focusing on the Ga<inf>2</inf>Al<inf>3</inf> and Ga<inf>3</inf>Al<inf>2</inf> compositions. The scintillation properties were systematically investigated as a function of Mg concentration. The results revealed that Mg co-doping strongly influenced both the light yield and the scintillation decay time. In particular, Y<inf>3</inf>Ga<inf>3</inf>Al<inf>2</inf>O<inf>12</inf>:Ce0.33at%,Mg0.033at% exhibited the highest light yield of 44,300 photons/MeV, comparable to that of Gd<inf>3</inf>Ga<inf>3</inf>Al<inf>2</inf>O<inf>12</inf>:Ce (GAGG:Ce) (46,000 photons/MeV), while maintaining a fast scintillation decay time of approximately 49 ns. In contrast, higher Mg concentration (0.2at%) led to a deterioration in both light yield and decay characteristics, suggesting the activation of non-radiative processes. For Y<inf>3</inf>Ga<inf>2</inf>Al<inf>3</inf>O<inf>12</inf>, the light yield was generally lower than that of Y<inf>3</inf>Ga<inf>3</inf>Al<inf>2</inf>O<inf>12</inf>, although low level Mg co-doping still improved performance compared with non-doped samples. These findings demonstrate that the optimal Mg concentration enables the simultaneous enhancement of light yield and reduction of scintillation decay time, and that Ga<inf>3</inf>Al<inf>2</inf> compositions are more favorable than Ga<inf>2</inf>Al<inf>3</inf> under low Mg doping. This study provides the first systematic evaluation of Mg co-doping dependence in YAGG and highlights its potential as a promising scintillator material for next-generation photon-counting computed tomography (PCCT). The results not only identify optimal compositions for improved scintillation performance but also provide a foundation for further optimization, including investigations of broader Mg concentrations, alternative alkaline-earth dopants, and the underlying mechanisms governing co-doping effects.

DOI： 10.1088/1742-6596/3157/1/012020

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その他リンク： https://iopscience.iop.org/article/10.1088/1742-6596/3157/1/012020/pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystals  

In this study, we developed and characterized novel scintillators with Ce: LiCaAlF<inf>6</inf>–CaF<inf>2</inf>–Li<inf>3</inf>AlF<inf>6</inf> and Ce: CaF<inf>2</inf>–LiF–Li<inf>3</inf>AlF<inf>6</inf> ternary systems for thermal neutron detectors. The eutectics were grown by the vertical Stochbarger-Bridgman (VB) technique, and their constituent phases were identified using powder X-ray diffraction and scanning electron microscopy. Radioluminescence spectra irradiated under an Ag-target X-ray tube and confirmed the 5d-4f and self-trapped exciton luminescence derived from Ce³⁺. Scintillation decay and pulse height measurements were performed using ²⁵²Cf and ⁶⁰Co sources. The Ce: CaF<inf>2</inf>–LiF–Li<inf>3</inf>AlF<inf>6</inf> sample exhibited approximately 5.6 times higher effective neutron sensitivity compared with a Ce: LiCaAlF<inf>6</inf> single crystal. A favorable decrease in the neutron discrimination threshold level (Q<inf>th</inf>) due to reduced γ-ray emission was observed. ⁶Li-enriched Ce: CaF-based scintillators hold potential for nuclear decommissioning applications.

DOI： 10.3390/cryst15090761

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Scientific Reports  

Complex oxide single crystals with melting points (MPs) above 2200 °C cannot be grown from the melt using iridium (Ir) or platinum (Pt) crucibles due to the MP limitations of these materials. To overcome this, we focused on the tungsten (W) crucibles, with MP above 3400 °C. The micro-pulling-down (µ-PD) method employing the W crucible and deoxygenated insulators enabled the growth of oxide single crystals with MP exceeding 2200 °C without any inclusions or deterioration of the W crucible. La<inf>2</inf>Zr<inf>2</inf>O<inf>7</inf> (MP: 2283 °C) and La<inf>2</inf>Hf<inf>2</inf>O<inf>7</inf> (MP: 2418 °C) single crystals with a pyrochlore structure were successfully grown using W crucibles, and they exhibited high transparency after annealing in air. Additionally, we achieved the growth of Lu<inf>3</inf>TaO<inf>7</inf> (MP: 2380 °C) single crystals with a density of 9.68 g/cm³. Lu<inf>3</inf>TaO<inf>7</inf> single crystal is a promising scintillator material for high-energy radiation detection due to its ultra-high density and potential for fast decay via Cherenkov light emission. The luminescence and scintillation properties of dopant ions can be clarified in single crystals with rare-earth (RE) ions. These results demonstrate that the advanced growth method is useful tool for the development and study of high-MP optical materials and scintillators.

DOI： 10.1038/s41598-025-12535-0

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Luminescence  

Optical thermometry is one of the promising methods of detecting temperature under harsh environments. In this study, for the development of a novel optical thermometer, we focused on Eu-doped (Y, Lu, Sc)<inf>2</inf>O<inf>3</inf> and grew single crystals using the micro-pulling-down method. Crystal growth was performed by systematically changing the ratio of Y to Lu, and the crystalline system and space group were identified to be cubic and Ia–3, respectively, by the powder X-ray diffraction analysis. From the photoluminescence emission spectra, the emission peaks attributed to Eu³⁺ ⁵D<inf>0</inf>–⁷F<inf>1</inf> and ⁵D<inf>1</inf>–⁷F<inf>1</inf> transitions were observed. The temperature dependence of these emission peaks was measured and evaluated using the fluorescence intensity ratio method to estimate the performance as the optical thermometer. It was found that Eu-doped (Y, Lu, Sc)<inf>2</inf>O<inf>3</inf> can be used as the optical thermometer in the temperature range from 430 K to 790 K. The relative sensitivity reached a maximum of 0.22 %K⁻¹ at 760 K.

DOI： 10.1016/j.jlumin.2025.121118

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the Korean Ceramic Society  

Single crystals of layered oxychalcogenide Sr<inf>2</inf>MCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf> (M = Co, Ni) have been successfully grown by the melt-solidification method. Thermal analysis and X-ray diffraction measurement results revealed that these compounds are congruent melting under a sealed environment similar to Sr<inf>2</inf>ZnCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf>, while melting points are slightly different. The plate-like single crystals on the order of mm² were obtained by melt solidification. The anisotropy of resistivity in Sr<inf>2</inf>CoCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf> showed that the resistivity in the c-axis direction was about 200 times higher than in the a(b)-axis direction, reflecting the two-dimensional crystal structure. These results indicate that there are several congruent melting layered mixed-anion compounds, even though they have complex crystal structures with multiple components. Thus, the single crystal growth method by melt-solidification under a sealed environment has the potential to be applied to other relative compounds.

DOI： 10.1007/s43207-024-00473-y

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Materials Chemistry C  

In recent decades, optical thermometry has gained significant attention due to its promising properties, such as non-contact measurement, temperature mapping and immunity to electromagnetic interference. It overcomes the limitations of conventional temperature measurement methods and offers additional benefits. However, the widespread adoption of optical thermometry requires an expanded operating temperature range and improved sensitivity. Therefore, in this study, we focused on solid-solution sesquioxides, which are expected not only to enable the growth of single crystals with a cubic structure but also to allow for a wider selection of luminescence centers. We evaluated the applicability of (Lu, Y, Sc)<inf>2</inf>O<inf>3</inf> single crystals doped with Pr³⁺ and Tb³⁺, which exhibit different temperature dependent behaviors, for optical thermometry. The optical temperature sensing properties evaluated using the fluorescence lifetime method revealed a maximal relative sensitivity of 1.53% K⁻¹ in the temperature range of 78-790 K for Pr³⁺, Tb³⁺:(Lu, Y, Sc)<inf>2</inf>O<inf>3</inf>. These results suggest that (Lu, Y, Sc)<inf>2</inf>O<inf>3</inf> co-doped with Pr³⁺ and Tb³⁺ is a promising candidate for optical thermometry.

DOI： 10.1039/d5tc00156k

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Scientific Reports  

A high-performance Ce³⁺-doped (Gd, Tb)<inf>3</inf>(Ga, Al)<inf>5</inf>O<inf>12</inf> (GTAGG: Ce) single crystal was engineered and characterized, demonstrating a high application potential for advanced X-ray imaging. A transparent 1-inch diameter single crystal was grown using the Czochralski method, demonstrating a significant advancement in large-scale scintillator production. Comprehensive characterization using X-ray diffraction and electron probe micro-analysis confirmed the crystal’s structural integrity. Photoluminescence and radioluminescence spectroscopy demonstrated efficient bidirectional energy transfer between Ce³⁺ and Tb³⁺ ions, a critical mechanism enhancing the performance of the scintillator. X-ray imaging tests were performed using crystals with a thickness of 100 μm at the Aichi Synchrotron Radiation Center. Comparison with the industry-standard LuAG: Ce scintillator showed that the GTAGG: Ce crystal produced 2.4 times higher light output and achieved a high spatial resolution of 0.85 μm. The results indicated that GTAGG: Ce is suitable for the next generation of high-performance X-ray imaging detectors in scientific and medical imaging applications.

DOI： 10.1038/s41598-025-96031-5

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その他リンク： https://www.nature.com/articles/s41598-025-96031-5

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystals  

Ce-doped Lu<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> has a high density, high luminescence efficiency even at high temperatures, and a high effective atomic number, making it a promising candidate for use as a radiation detector in medical devices and resource exploration equipment. In this study, we grow and characterize Pr³⁺ and Ce³⁺-doped Lu<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> single crystals by systematically varying the Ce³⁺ to Pr³⁺ ratio to further improve scintillation properties. The optical characterization results show a bidirectional energy transfer: from the Pr³⁺ 5d levels to the Ce³⁺ 5d levels and from the Ce³⁺ 5d levels to the Pr³⁺ 4f levels. Consistently with this result, the PL decay time of emission from the Pr³⁺ 5d–4f transition tends to become faster as the Ce³⁺/Pr³⁺ ratio increases, due to the energy transfer from the Pr³⁺ 5d levels to the Ce³⁺ 5d levels. Additionally, (Ce<inf>0.0022</inf> Pr<inf>0.0016</inf> Lu<inf>0.9962</inf>)<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> exhibits a high light yield comparable to Ce-doped Lu<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> and a slightly faster decay time than Ce-doped Lu<inf>2</inf>Si<inf>2</inf>O<inf>7</inf>.

DOI： 10.3390/cryst15030202

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（国際会議プロシーディングス）   出版者・発行元：2025 IEEE International Symposium on Applications of Ferroelectrics Isaf 2025 Proceedings  

Congruent composition of the 2-inch Ca3 TaGa Al3 Si2 O14 (CTGAS) bulk single crystal was determined by Inductively Coupled Plasma (ICP) analysis and the congruent composition calculated from the results of ICP analysis was different from the stoichiometric composition. 2inch Ca3 TaGa3 Si2 O14 (CTGS) bulk single crystals without any cracks could be grown by the continuous crystal growth using starting materials with the congruent composition from the first to the sixth growths.

DOI： 10.1109/ISAF61233.2025.11235118

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Alloys and Compounds  

The development of scintillators with co-doping mechanisms has received significant attention due to the resulting enhancements in luminescence and scintillation properties. Scintillators such as Ce-doped (Gd,Tb)<inf>3</inf>(Al,Ga)<inf>5</inf>O<inf>12</inf> have been recognized for their improved performance, attributed to the effective energy transfer between Ce³⁺ and Tb³⁺ ions. Nevertheless, the presence of Gd³⁺ introduced complexities, as its absorption lines strongly overlap with those of Tb³⁺, thus masking the details of mechanisms of the Tb³⁺↔Ce³⁺ energy transfer. This study endeavored to elucidate this mechanism by comparing the luminescence characteristics of Ce,Tb co-doped Y<inf>3</inf>Al<inf>2</inf>Ga<inf>3</inf>O<inf>12</inf> (YAGG) and Gd<inf>3</inf>A<inf>2</inf>Ga<inf>3</inf>O<inf>12</inf> (GAGG) single crystals. Through detailed photoluminescence spectral analysis, it was discerned that GAGG exhibited a more robust Tb³⁺↔Ce³⁺ energy transfer, as evidenced by a marked extension in the decay time of Ce³⁺ luminescence. Furthermore, GAGG demonstrated superior integrated radioluminescence intensity across all compositions which is a result of efficient energy transfer from Gd³⁺ to the luminescence centers. Additionally, comparative thermally stimulated luminescence glow curves, revealed distinctive spectral features between YAGG and GAGG, underscoring the complexity of their luminescence mechanisms. This comparative study not only augmented our comprehension of the intricate energy transfer processes in Ce, Tb co-doped garnet scintillators but also underscored the potential for tailored scintillator development through strategic ion co-doping.

DOI： 10.1016/j.jallcom.2024.176550

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystengcomm  

A three-dimensional-micro-pulling-down (3D-μ-PD) method was developed for the growth of 3D shaped single crystals, and spring-shaped sapphire single crystals were grown by the 3D-μ-PD method using Mo crucibles with different dies. The shape of the die significantly affected the growth stability and shape control of the spring-shaped single crystals. Spring-shaped sapphire single crystals with a smaller helical pitch and larger helical radius were obtained easily using a Mo crucible with a sharp conical die compared to that with a blunt conical die. However, spring-shaped sapphire single crystals grown using a Mo crucible with an inverse conical die can be obtained with smaller helical pitches, and the shape of the cross-sectional plane is a horizontally extended elliptical shape. The difference in the shape of the cross-sectional plane for spring-shaped sapphire single crystals affects the crystallinity and mechanical properties. Furthermore, crystals grown using the Mo crucible with the inverse conical die exhibited a larger shrinkage rate in the compression test.

DOI： 10.1039/d4ce00560k

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Luminescence  

Driven by the pursuit of optimizing the luminescent properties of garnet-based single crystals for X-ray imaging applications, this work reports on the successful synthesis and in-depth characterization of GYAGG crystals doped with Ce³⁺ or Tb³⁺ ions, and doubly-doped with both of them. Micro-pulling down synthesis yielded crystals with a single cubic phase confirmed by X-ray diffraction. Photoluminescence (PL) and radioluminescence (RL) measurements on Ce³⁺,Tb³⁺ co-doped GYAGG revealed bidirectional energy transfer processes. Characteristic broadband 5d<inf>1</inf>→4f emission of Ce³⁺ centers peaking at 530 nm and narrow 4f→4f emission lines of Tb³⁺ ions starting from ⁵D<inf>4</inf> level within 480–630 nm were observed. At higher doping levels, cross-relaxation in Tb³⁺ pairs resulted depleted ⁵D<inf>3</inf> state and only the emission from ⁵D<inf>4</inf> one was observed in the spectra. Analysis of PL decay characteristics corroborated the spectral observations, confirming progressively decreasing Ce³⁺ decay time (down to 40 ns at 15 % Tb³⁺) due to enhanced Ce³⁺→Tb³⁺ energy transfer. Similarly, the Tb³⁺ decay time accelerated by more than 60 % after the Ce³⁺ co-doping. Notably, co-doping with 0.5 % Ce³⁺ and 10–15 % Tb³⁺ doubled the luminescence intensity of RL spectra compared to 0.5 % Ce³⁺-doping alone, attributed to the increased density of emitting centers.

DOI： 10.1016/j.jlumin.2024.120663

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Ceramics International  

We have successfully grown single crystals of layered mixed-anion compound Sr<inf>2</inf>ZnCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf> by a simple melt-growth method. Single crystals of the layered oxychalcogenides Sr<inf>2</inf>ZnCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf> were grown by melt-solidification of stoichiometric raw materials. Plate-like single crystals were obtained, and the maximum size of crystals was 2.5 × 1.4 mm². Thermal analysis result indicates simple melting-solidification-like behavior, and the size of crystals increases significantly above the melting point revealed by this measurement. X-ray rocking curve (XRC) measurement results of the single crystal showed no peak splitting, with a narrow full width half maximum of 30 and 97 arcsec in (105) and (0012) peaks, respectively. The electrical conductivity of single crystals on the a(b) plane was 4.34 × 10⁻¹ S/cm at room temperature. Obtained single crystals were transparent, and the absorption edge was observed around 560 nm in the transmittance measurement. Although layered oxychalcogenide Sr<inf>2</inf>ZnCu<inf>2</inf>Se<inf>2</inf>O<inf>2</inf> has a complex composition and structure, this compound exhibits congruent melting behavior in a sealed environment. This feature enables us to grow single crystals of mixed-anion compounds easily by the melt-growth method.

DOI： 10.1016/j.ceramint.2024.03.263

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Optical Materials X  

Pr-doped scintillators are attracting attention because of their potential applications in medical devices. In this study, we focused on Pr-doped (La, Y)<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> scintillators to grow single crystals by the micro-pulling-down method and to evaluate their optical and scintillation properties. From the powder XRD results, the crystal structure and the space group were identified to be monoclinic and P2<inf>1</inf>/n, respectively. The results of optical and scintillation characterization show that the luminescence from the Pr³⁺ 5d<inf>1</inf>–4f transition increases with increasing Pr³⁺ concentration. The maximum light yield was also obtained for the sample with the highest Pr³⁺ concentration. The Pr-doped (La, Y)<inf>2</inf>Si<inf>2</inf>O<inf>7</inf> single crystal shows promising properties for application in radiation detection.

DOI： 10.1016/j.omx.2024.100318

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

For the decommissioning of Fukushima Daiichi Nuclear Plants, a novel real-time dose-rate monitor consisting of a scintillator, 100-m long optical fiber and CCD spectrometer has been proposed, and this scintillation material is required to have an emission wavelength of longer than approximately 650 nm. In this paper, as a candidate material for the system, we focused on Ce/Cr co-doped Gd<inf>3</inf>Ga<inf>5</inf>O<inf>12</inf> (Ce/Cr:GGG) single crystals grown by the micro-pulling down method. Since the light output of this material was expected to depend on the Cr³⁺ concentration, we investigated the relationship between Cr segregation and luminescence properties in Ce/Cr:GGG crystal. Generally, a single photon counting method is not available to evaluate its light output accurately due to the long decay time, we used a novel technique “emission-intensity two-dimensional- mapping method” (2D-image method) to verify the light intensity at each point of the sample. This method realized estimation of the light intensity within the sample, though segregation of Cr³⁺ is observed. The results showed that Cr was concentrated in the center part along the radial direction in the grown crystals, while all parts had an emission wavelength of approximately 730 nm excited by X-ray. Using the 2D-image method, emission intensity was found to correspond to the Cr concentration, and its correlation coefficients between emission intensity and Cr concentration were over 0.8. We found that our material is available for the monitoring system when the Cr dense part of the crystal is cut and used.

DOI： 10.1016/j.jcrysgro.2024.127581

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IOP Publishing  

Abstract

The growth of Er-doped La₂Hf₂O₇ (LHO:Er) single crystals with a high mp of 2413 °C was achieved by the melt-growth method using a tungsten (W) crucible. Polished LHO:Er specimens were obtained from the as-grown crystals. The full width at half maximum of the X-ray Rocking curve on the (222) diffraction peak was 599 arcsec, and the crystals have relatively low crystallinity. The photoluminescence spectra of the polished LHO:Er specimen showed emission peaks originating from the Er³⁺ ions in both the visible and IR wavelength ranges. It also exhibited scintillation light under X-ray irradiation.

DOI： 10.35848/1347-4065/ad1e97

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その他リンク： https://iopscience.iop.org/article/10.35848/1347-4065/ad1e97/pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

A calculation model for predicting the temperature characteristics of the double-layered resonator (DRL) was developed by using the total strain ratio including the influence of the waves reflected at the bonding boundary. The validity of the model proposed was examined from the comparison between the measured and calculated results for a DRL specimen consisting of 129.55°Y- and 0°Y-quartz substrates. The calculation results of the model proposed demonstrated that it is possible to predict the trends of changes in experimental values of temperature characteristics not only in the 1st-order mode but also in the higher-order modes. In addition, the changes in the particle displacement distribution and temperature characteristics of the DLR obtained by the model proposed were also in good agreement with the results of finite element method analysis. The proposed model is expected to greatly contribute to the design of DLRs with high excitation efficiency and excellent temperature characteristics.

DOI： 10.35848/1347-4065/ad1fb1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

In our search for cross-luminescence (CL) scintillators suitable for fast-timing applications, we have chosen CsMgF<inf>3</inf> as one of the perspective candidates. During the attempts to grow CsMgF<inf>3</inf> by the micro-pulling-down method, we have revealed the presence of Cs<inf>4</inf>Mg<inf>3</inf>F<inf>10</inf> which is in contradiction with the published equilibrium phase diagram. The Cs<inf>4</inf>Mg<inf>3</inf>F<inf>10</inf> has an orthorhombic structure, consisting of face-sharing MgF<inf>6</inf> octahedra triplets (4 triplets per unit cell), joined to 4 other triplets by corner sharing. These chain-like structures are separated by Cs⁺ ions. Moreover, Cs<inf>4</inf>Mg<inf>3</inf>F<inf>10</inf> is non-hygroscopic despite the hygroscopic nature of CsF. The best crystals were grown from CsF-rich melt to suppress off-stoichiometry due to CsF evaporation during crystal growth. Both radioluminescence spectra and scintillation decay kinetics exhibit complex character and the presence of CL in Cs<inf>4</inf>Mg<inf>3</inf>F<inf>10</inf> is still under question. However, due to relatively low scintillation efficiency and the presence of slow components in scintillation decay, Cs<inf>4</inf>Mg<inf>3</inf>F<inf>10</inf> is not suitable for fast-timing applications.

DOI： 10.1016/j.jcrysgro.2024.127568

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

³He gas detectors have been commonly used in applied technology related to thermal neutron detectors; however, owing to the depletion of ³He, applications using solid-state scintillators are expanding. In recent years, our group has reported a novel Tl:CsI/⁶LiBr eutectic scintillator for thermal neutron detection, which has excellent light yield and (n,γ) discrimination ability. In practical applications of eutectic scintillators, achieving eutectic production precisely at the eutectic point is crucial to ensure a high production yield and the development of a uniform eutectic structure. However, the phase diagram of the CsI-LiBr system has not yet been reported. In this study, the phase diagram obtained from calorimetry was investigated. Furthermore, eutectic fabrication was performed at the eutectic point, and the neutron response was evaluated.

DOI： 10.1016/j.jcrysgro.2023.127543

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担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

Mg<inf>2</inf>Si/Si eutectics are grown from melt by the Vertical Bridgman method using a carbon crucible at three pulling rates. All the Mg<inf>2</inf>Si/Si eutectics are composed of Mg<inf>2</inf>Si and Si phases, and the eutectic structure becomes finer with an increase in the pulling rate. Increasing the pulling rate systematically decreases the thermal conductivities of the Mg<inf>2</inf>Si/Si eutectics, suggesting that a decrease in the thermal conductivity is attributed to an increase in phonon scattering at the boundaries between the two phases. The power factor and figure of merit of the Mg<inf>2</inf>Si/Si eutectics are larger than those of Mg<inf>2</inf>Si above 400 °C because of the increase in the Seebeck coefficient. The figure of merit, ZT, of the Mg<inf>2</inf>Si/Si eutectics solidified at a 10³ mm/min pulling rate reached 0.076 at 600 °C.

DOI： 10.1016/j.jcrysgro.2023.127533

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystals  

The ³He gas is commonly used for the detection of thermal neutrons. However, with the depletion of ³He gas, there is a need to develop new solid scintillators for thermal neutron detection. Solid scintillators containing ⁶Li, which have large neutron capture cross-sections and a large amount of energy released by transmutation reactions, are commonly used as alternative candidates. However, only single-crystal scintillators are currently used, and their ⁶Li concentration is limited by their chemical composition. In this study, we designed, grew, and evaluated a new eutectic scintillator, Rb<inf>2</inf>CeCl<inf>5</inf>/LiCl, which can improve the ⁶Li concentration compared with single-crystal scintillators. Rb<inf>2</inf>CeCl<inf>5</inf>, which was selected as the scintillator phase, has excellent scintillator properties (light yield: 36,000 photons/MeV, decay time: mostly 24 ns, slightly 153 ns), and is less deliquescent than other halide scintillators. The crystal grown using the vertical Bridgman method exhibited a eutectic phase composed of Rb<inf>2</inf>CeCl<inf>5</inf> and LiCl. The eutectic crystals exhibited Ce³⁺ 5d-4f emissions, with a peak between 360 and 370 nm. The Rb<inf>2</inf>CeCl<inf>5</inf> phase was identified as the luminescent phase via cathodoluminescence mapping, and 16,000 photons/neutron of the light yield and 56.1 ns of the decay time were observed. This study indicates that the Rb<inf>2</inf>CeCl<inf>5</inf>/LiCl eutectic scintillator is a promising candidate for use in thermal neutron detectors.

DOI： 10.3390/cryst14020154

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Instrumentation  

Real-time dose-rate monitoring system under the high dose-rate situation is required for the decommissioning of Fukushima Daiichi Nuclear Plants to remove the debris remaining inside the plants. We have proposed a dose-rate monitor consisting of a scintillator, over 100-m long optical fiber and CCD spectrometer. Some noises with a dominant emission wavelength of below 550 nm originating from the optical fiber itself must be separated from the signal from the scintillator, and the signal region has been defined as 650–1000 nm to use significant data, up to now. In this paper, we investigated if the noise region defined as below 550 nm can be supporting data for the monitoring system, because such noises are expected to include position information through the fiber. In the emission spectrum, the intensities of the noise emission or absorption band are expected to depend on the position of the fiber, and we demonstrated such dependence, “one-dimensional dose-rate distribution”, with 20 m-long optical fiber and CCD spectrometer. Optical fiber was placed around a ⁶⁰Co source with an activity of approximately 60 TBq, and emission spectra of the fiber were acquired with different dose-rate conditions from 10 to 700 Gy/h. The noise intensities were well fitted with the power function as a function of the product of fiber length and dose rate, and we found that fiber noise has rate information in one-dimensional imaging.

DOI： 10.1088/1748-0221/19/02/C02053

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Ceramics International  

Scintillators are used not only as single crystals in radiation detection systems but also as arrays, columns, and fibers. In this study, a novel optical-guiding crystal scintillator (OCS) was fabricated using an Eu:SrI<inf>2</inf> crystal as the core and borosilicate glass as the cladding. The OCS has an elongated shape and can be flexibly processed like an optical fiber. Furthermore, because inorganic scintillator crystals are used as the core, the OCS has high sensitivity to high-energy radiation, such as γ- and X-ray radiation, unlike plastic scintillators. In this study, by observing the cross section of the fabricated OCS, identifying the crystal structure, and investigating the radioluminescence spectrum under X-ray irradiation, OCS fabrication in accordance with the OCS design specifications was confirmed, and the SrI<inf>2</inf> crystal structure and Eu²⁺ 5d–4f luminescence were maintained. The γ-ray responses, such as light yield and decay time, were also investigated.

DOI： 10.1016/j.ceramint.2022.12.264

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Materials Today Communications  

The crystal structures of Ca<inf>3</inf>Nb(Ga,Al)<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (CNGAS) and Ca<inf>3</inf>Ta(Ga,Al)<inf>3</inf>Si<inf>2</inf>O<inf>14</inf> (CTGAS) single crystals are investigated in this study to reveal the relationship between their crystal structures and acoustic physical properties. The positional parameters of each element for the CNGAS and CTGAS single crystals are determined with high accuracy, whereas the bond lengths and bond angles are calculated using the positional parameters. Analysis results of the crystal structures suggest that the increase of bond angles, O2-Si-O2 and Si-O2-(Ga,Al), in the O2-Si-O2-(Ga,Al) line causes the increase of their anisotropy of crystal structures. Elastic constants related to the z-axis, i.e., c^E<inf>33</inf> and c^E<inf>44</inf>, increase significantly after Al substitution, which is attributed to the increase in the anisotropy of the crystal structures.

DOI： 10.1016/j.mtcomm.2023.107506

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Solid State Chemistry  

In this study, charge compensation was performed by co-doping Na ⁺ ions at the Ca²⁺ sites of Ce-doped LiCaAlF<inf>6</inf> single crystals to prevent the generation of cation vacancies owing to Ce³⁺-doping at the Ca²⁺ sites. Consequently, an improved radiation resistance and increased light yield under neutron irradiation was achieved. In contrast, the Al metal of the starting material used as a substitute for AlF<inf>3</inf> significantly increased the effective segregation coefficient k<inf>eff</inf> of the Eu²⁺ ions in Eu-doped LiCaAlF<inf>6</inf> and Eu-doped LiSrAlF<inf>6</inf> single crystals. The Al metal and EuF<inf>3</inf> in the starting materials produced EuF<inf>2</inf> via a chemical reaction, and the Eu²⁺ ions in EuF<inf>2</inf> could be substituted at the Ca²⁺ and Sr²⁺ sites. In addition, the Ca/Sr ratio control of the Li(Ca,Sr)AlF<inf>6</inf>:Eu solid-solution scintillator single crystals improved the light yield through band-gap control, and the Li(Ca,Sr)AlF<inf>6</inf>:Eu single crystal with a 25% Sr concentration exhibited the highest light yield.

DOI： 10.1016/j.jssc.2023.124127

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

Acoustic properties of Ga-Sn-Zn (GSZ) liquid alloy coupler with high acoustic impedance were investigated to evaluate materials with high acoustic impedance. GSZ liquid alloy was prepared and its longitudinal wave velocity and attenuation coefficient were measured using the plane-wave ultrasonic material characterization system. Density of the GSZ liquid alloy was also measured by a constant volume expansion method. The acoustic impedance of the GSZ was 12 times higher than that of the water. Attenuation coefficient of GSZ is much smaller than that of water, exhibiting 7.6 dB mm⁻¹ for water and 0.5 dB mm⁻¹ for GSZ at 200 MHz. Considering the reflection and transmission coefficients at each medium boundary calculated from the experimentally obtained acoustic impedance, it was suggested that the amplitude of the reflected wave from the back surface of the Ir sample can be made about 30 times larger with the GSZ coupler than with the water coupler.

DOI： 10.35848/1347-4065/acb272

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Nuclear Science  

In this study, Ce:6LiCl/LaCl3 with a high 6Li concentration was developed as a novel thermal neutron scintillator, in which Ce3+ serves as an activator for the LaCl3 phase. The Ce:6LiCl/LaCl3 eutectic was grown in a quartz ampoule (inner diameter: 4.0 mm) using the Bridgman-Stockbarger technique. The grown eutectic contained 0.038 mol/cm36Li, which is greater than that found in commercially available scintillators such as LiCaAlF6 single crystals and Li glass. The Ce:6LiCl/LaCl3 eutectic has a lamellar eutectic structure and is optically transparent. A 350-nm emission due to Ce3+ 4f-5d transition was observed. The light yield under neutron irradiation was estimated to be 5.0 times higher than that of Li glass. In this eutectic, the 6Li ( n , a 3 H reaction made the 6LiCl phase to act as the neutron capture phase and LaCl3 to act as the scintillator phase.

DOI： 10.1109/TNS.2023.3271639

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Nuclear Science  

In this study, a novel thermal neutron scintillator of Tl:CsI/LiBr was developed. The eutectics were fabricated at various growth rates and investigated their scintillation properties. As a material design guideline, Tl:CsI, which has an excellent ratio, was selected as the scintillator phase to realize high light yield at the energy of rays and tritons generated by the nuclear transmutation reaction with 6Li and LiBr, which has a refractive index close to that of CsI, was selected as the neutron capture phase. Radioluminescence (RL) measurement under X-ray irradiation was also performed to obtain the emission spectrum of the eutectics. The light yield and decay time for thermal neutron were measured using 252Cf and were much higher than those of conventional scintillators for thermal neutron. Furthermore, fabricated eutectic can have the higher sensitivity to thermal neutron due to the high 6Li concentration compared to conventional single-crystal scintillators. Therefore, we have succeeded in developing a promising scintillator material.

DOI： 10.1109/TNS.2023.3278465

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担当区分：最終著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Alloys and Compounds  

The pure and strontium (Sr) substituted LaFeO<inf>3</inf> polycrystalline samples were prepared through solid state synthesis process and good quality single crystals were successfully grown by four mirror optical floating zone technique for dielectric and magnetic measurements. The feed and seed rods were prepared by employing an external pressure of about 70 MPa and sintered at 1350 ⁰C on 12 h. The orthorhombic structure of the pure and Sr substituted materials were confirmed by powder X-ray diffraction analysis. The nonappearance of shoulder peaks in the Sr substituted LaFeO<inf>3</inf> sample reveals single-phase crystal system without any sub-grain boundaries. The composition of the pure and substituted crystals was confirmed by EDS (energy dispersive X-ray spectroscopy) analysis. The dielectric studies were carried out on both samples in the temperature range from 300 to 900 K for the frequency range from 2.5 kHz to 125 kHz. The grown crystals show their Neel temperature at 742 K and the dielectric constant value increased for substituted LaFeO<inf>3</inf> crystal. A colossal dielectric behavior and electrical conductivities were analyzed through dielectric studies. The activation energies of pure and Sr substituted LaFeO<inf>3</inf> crystals were estimated to be 0.19 and 0.16 eV respectively. Magnetic properties of the developed crystals were tested by M-H loop. The M-T plot of Sr substituted LaFeO<inf>3</inf> crystal was discussed with Zero field cooled (ZFC) and Field cooled (FC) modes for its potential magnetic application.

DOI： 10.1016/j.jallcom.2023.169161

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

In this study, optical-guiding crystal scintillator (OCS) and bundled plates were fabricated. Considering the performance and melting point of halide scintillators and the softening point of glass, Tl:CsI was selected as the fiber core and borosilicate glass as the cladding. Thus, the fabricated OCS had a scintillator in the core and glass in the cladding. The scintillator was remelted and unidirectionally solidified to remove the voids in the OCS and form a single crystal. Consequently, the OCS served as a scintillator fiber with excellent optical-guiding performance and high sensitivity to γ- and X-rays. An OCS plate was also fabricated using bundles of OCSs with diameters of several tens of microns. The developed OCS plate is expected to be a high-resolution and high-sensitivity imaging plate because of its excellent optical-guiding performance.

DOI： 10.35848/1347-4065/acb3d1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Aip Advances  

Scintillators are key components in high-energy x-ray detectors for x-ray computed tomography, which are applied in medical diagnosis, nondestructive testing, and security inspection. Scintillators in x-ray imaging are required to have both high spatial resolution and sensitivity; however, a trade-off between spatial resolution and sensitivity exists. To improve the sensitivity of a scintillator, its thickness must be increased; however, spatial resolution deteriorates with increasing thickness. Here, we developed a well-aligned Tb-doped GdAlO3-αAl2O3 phase-separated scintillator fiber (PSSF) with a diameter of 1.25-μm by a micro-pulling-down method. The luminescence, scintillation, and imaging performances of a grown PSSF sample were evaluated. X-ray-induced radioluminescence measurements of the sample showed Tb3+ 4f-4f emissions in the wavelength range of 470-700 nm, and the maximum emission peak was at 550 nm. The contrast transfer function at 10 lp/mm was 82% for both 270 and 500 μm-thick PSSF samples. We calculated the luminescence index, which is the product of the scintillator's light yield and sensitivity, of the samples and compared their values with commercially available conventional CsI:Tl columnar scintillators. The Tb-doped GdAlO3-αAl2O3 PSSF exhibits higher contrast transfer function and luminescence index values at above 60 keV x-ray region compared with the tested conventional scintillators.

DOI： 10.1063/5.0136069

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Applied Physics Express  

Scintillation properties of a flexible optical-guiding crystal scintillator with a thallium-doped CsI (Tl:CsI) crystal and borosilicate glass as the core and cladding, respectively, are reported. The as-fabricated optical-guiding crystal scintillator exhibits a light yield of 31,000 photons MeV⁻¹ under 662 keV γ-ray irradiation. The recrystallized sample is transparent and provides a higher light yield of 54,000 photons MeV^-1, which is comparable to that of single-crystal Tl:CsI. The decay times are 400 ns (28%) and 1,350 ns (72%). This material can serve as a scintillator fiber with high sensitivity to γ- and X-rays, high light yield, and energy discrimination.

DOI： 10.35848/1882-0786/acb891

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：MDPI AG  

In recent years, thermal neutron detection using scintillators has been used in a wide range of fields. Thus, the development of scintillators with a higher light yield, faster decay, and higher sensitivity for thermal neutrons is required. In this study, K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were developed as novel eutectic scintillators for thermal neutron detection. LiCl was selected as the neutron capture phase and K2CeCl5 and CeCl3 were used as the scintillator phases. The eutectics of K2CeCl5/6LiCl and CeCl3/SrCl2/6LiCl were prepared using the Vertical Bridgman method and the phases were identified by scanning electron microscopy and powder X-ray diffraction measurements. The results of radioluminescence measurements under Ag source X-ray tube irradiation confirmed that the 5d-4f emission derived from Ce3+. The cathodoluminescence spectra and thermal neutron responses of the prepared eutectics were measured to evaluate their optical properties.

DOI： 10.3390/cryst12121795

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Frontiers in Materials  

The atomic positions and displacements of atoms around the Ta atom in piezoelectric materials Ca<inf>3</inf>TaGa<inf>3</inf>Si<inf>2</inf>O<inf>7</inf> (CTGS) and Ca<inf>3</inf>TaGa<inf>1.5</inf>Al<inf>1.5</inf>Si<inf>2</inf>O<inf>7</inf> (CTGAS) were investigated at 100 K by Ta-Lα X-ray fluorescence holography (XFH). The experimental atomic images were compared with the simulated ones using the crystal structures of CTGS and CTGAS, which were determined by single crystal X-ray diffractometry (SC-XRD). The atomic positions agreed between XFH and SC-XRD experiments. With the help of XFH simulation, the displacements of Ta, Ca, Si, and Ga atoms relative to the Ta atom were qualitatively analyzed using experimental atomic image intensities. The relative displacement of the Ca atom was increased by Al substitution, while those of the Ta and Ga atoms were decreased. The first principles calculation based on density-functional theory (DFT) was performed to understand bonding character between constituents. The evaluation of the crystal orbital Hamilton population (COHP) clarified that the Ca-O bond has strong ionic character different with the other bonds, suggesting that the positional shift of the Ca atom is responsible for the piezoelectricity in CTGS. The effect of Al substitution on piezoelectricity was also considered based on the change in the Ca-O bond.

DOI： 10.3389/fmats.2022.977371

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Crystals  

The technology to grow single crystals of the required shape directly from a melt has been researched extensively and developed in various industries and research fields. In this study, a micro-pulling-down method and a Mo crucible were applied to the shape-controlled crystal growth of Y (Formula presented.) Al (Formula presented.) O (Formula presented.) :Ce (YAG:Ce). Three types of Mo crucibles with different die shapes were developed. Stable crystal growth of more than 50 mm in length was achieved with the same shape as the die, and scintillation light output of ~20,000 ph/MeV, which is comparable with those of the YAG:Ce crystal grown by Cz method, were obtained. The transmittance of grown crystals above 500 nm was above 70%. The standard deviation ((Formula presented.)) of the scintillation light output at each position of the 50-mm-long sample was found to be within ±16%.

DOI： 10.3390/cryst12091215

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Optical Materials X  

In this study, Tl:CsI/CsCl/KCl ternary eutectic scintillators were grown using the vertical Bridgman–Stockbarger method by unidirectional solidification. The CsI and KCl phases were elongated along the growth direction, based on backscattered electron imaging (BEI) observations. The Tl:CsI scintillator phase grew as a matrix, which can be used to create optical waveguides for scintillation light. The expected Tl⁺ emission peak was observed at 550 nm under X-ray excitation. This emission was attributed to the self-trapped excitons perturbed by TI⁺ in Tl:CsI. The decay time of the Tl:CsI/CsCl/KCl eutectic was 285 ns, and its light output was estimated to be 10,800 photons/MeV.

DOI： 10.1016/j.omx.2022.100159

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

(Ce0.002 Y0.998-x Lu x )AlO3 (x = 0.000, 0.010, 0.100, 0.200) single crystals were grown and characterized to clarify the effects of Lu substitution in Ce:YAlO3 on its crystal structure, optical properties and thermal stability of Ce3+ luminescence. The lattice constants of (Ce0.002 Y0.798 Lu0.200)AlO3 were comparable to those of Ce:YAlO3, so the crystal structure was not significantly influenced by Lu substitution. Concerning the optical characterization, the absorption and emission spectra were almost the same regardless the amount of Lu substitution. This result is consistent with the assumption that the crystal field is not influenced by Lu substitution. The temperature dependences of the photoluminescence decay time showed that the quenching temperature (T 50%) tends to increase with the increasing Lu concentration. We conclude that the leading quenching mechanism is the thermally activated ionization which is suppressed by the Lu substitution in Ce:YAlO3.

DOI： 10.35848/1347-4065/ac7271

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その他リンク： https://iopscience.iop.org/article/10.35848/1347-4065/ac7271/pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

The influence of the reflected waves at the bonding boundary on the resonance waveform and temperature characteristics was investigated using α-quartz (QZ). The double-layered resonator specimen was fabricated using 129.55°Y-and 0°Y-cut QZ substrates with the thickness ratio x = 0.520. The temperature characteristic of the 1st and 2nd resonance modes at the range from 100 °C to 300 °C was deviated from the calculated values estimated by the equations considering thickness ratio and electric flux density ratio proposed in the previous work. Considering the phase matching conditions, it was clarified that the reflected waves at the bonding boundary are in phase in the lower acoustic impedance substrate and out of phase in the other substrate for the 1st mode, so the temperature characteristics are mainly dominated by that of the lower acoustic impedance substrate. In contrast, these relationships are reversed for the 2nd mode.

DOI： 10.35848/1347-4065/ac4a03

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その他リンク： https://iopscience.iop.org/article/10.35848/1347-4065/ac4a03/pdf

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

A 6LiBr/CeBr3 eutectic thermal-neutron scintillator, with a high 6Li concentration, was developed using the vertical Bridgman method. The grown eutectic contained an 6Li molar ratio of 35%, which is higher than those of the commercial neutron scintillators such as Ce:LiCaAlF6 and Ce:Cs2LiYCl6. Furthermore, it showed optical transparency and a lamellar eutectic structure elongating along the growth direction. The synthesized eutectic showed emission peaks at 360 and 380 nm, originating from the Ce3+ 5d-4f transition in the CeBr3 scintillation phase. The scintillation performance of 6LiBr/CeBr3 was evaluated under X-ray, γ-ray, and neutron irradiation to corroborate its neutron detection potential.

DOI： 10.35848/1347-4065/ac4076

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Japanese Journal of Applied Physics  

In this study, a large-size eutectic scintillator of Tb-doped BaCl2/NaCl/KCl was grown using the Czochralski (Cz) and halide vertical Bridgman methods (H-VB). The suitability of these two growth methods for growing the eutectic was compared. Finally, 1 inch diameter eutectic bulks were obtained using the H-VB method. The Tb3+-derived strongest intensity peak at approximately 550 nm was observed by X-ray irradiation. An approximately 3 × 3 mm transparent eutectic wafer was cut and polished from the grown eutectic bulk. An imaging test using α-ray was performed using the grown eutectic, a fiber optic plate, and an electron-multiplying CCD camera. The resolution performance for radiation-imaging applications was evaluated.

DOI： 10.35848/1347-4065/ac3b23

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Optical Materials X  

In this study, it was demonstrated that Zn<inf>3</inf>Ta<inf>2</inf>O<inf>8</inf> crystals containing zinc oxide with high vapor pressure can grow in melt by the shielded arc melting method. The radiation response characteristics of the crystals were evaluated. The grown crystals showed an emission peak at 410 nm, ascribed to self-trapped excitation, Ta⁴⁺–O²⁻. The full width at half maximum of the X-ray rocking curve was 655 arcsec. The light output under 662 keV gamma-ray irradiation of Zn<inf>3</inf>Ta<inf>2</inf>O<inf>8</inf> was approximately 4,700 photons/MeV. The decay time was 17.3 μs? Thus, the shielded arc melting method was shown to be a quick and economic growth technique for the survey of new scintillator materials containing high-vapor-pressure starting components.

DOI： 10.1016/j.omx.2022.100149

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

Ce-doped LaCl<inf>3</inf>/AECl<inf>2</inf> (AE = Mg, Ca, Sr) system eutectics were explored. Ce-doped LaCl<inf>3</inf>/ AECl<inf>2</inf> (AE = Mg, Ca, Sr) eutectics were grown using the Bridgman–Stockbarger method in quartz ampoules. In the case of AE = Mg, Ca, eutectics with submicron-diameter phase-separated scintillator fibers (PSSFs) structure were observed. In the case of AE = Sr sample, a solid solution of La<inf>0.708</inf>Sr<inf>0.292</inf>Cl<inf>2.708</inf> was observed. The plate sample from the grown eutectics has some transparency. The grown eutectic structure showed a mixture of rods and plates shape. This mixed structure was aligned with a length of around 100–400 μm. The Ce:LaCl<inf>3</inf>/CaCl<inf>2</inf> eutectic showed 345 nm emission ascribed to Ce³⁺ 4f-5d transition under X-ray excitation. The Ce:LaCl<inf>3</inf>/CaCl<inf>2</inf> sample resulted in the highest light output of 9,000 photon/MeV, which is comparable to the previously reported eutectic scintillator Ce:GdAlO<inf>3</inf>/α-Al<inf>2</inf>O<inf>3</inf>, 9500 photon/MeV. Scintillation decay time of the Ce:LaCl<inf>3</inf>/CaCl<inf>2</inf> sample under 662 keV gamma-ray excitation was 26.8 ns (26%) and 282 ns (74%).

DOI： 10.1016/j.jcrysgro.2022.126549

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment  

In this study, Ce:⁶LiBr/LaBr<inf>3</inf> eutectic with a high Li concentration was developed as a novel thermal neutron scintillator. Ce served as an activator for the LaBr<inf>3</inf> phase, and Ce:⁶LiBr/LaBr<inf>3</inf> eutectics were grown via the vertical Bridgman method in quartz ampoules (inner diameter = 4 mm). In the eutectic, the ⁶LiBr phase worked as the neutron capture phase by the ⁶Li (n, a) ³H reaction, and Ce:LaBr<inf>3</inf> worked as the scintillator phase. The Ce:⁶LiBr/LaBr<inf>3</inf> eutectic exhibited a lamellar eutectic structure and optical transparency, as well as 350 and 380 nm emission due to Ce³⁺ 5d-4f transition. The light yield under neutrons excitation was estimated to be 74000 photons/neutron. The scintillation decay time was 18.7 ns.

DOI： 10.1016/j.nima.2022.166384

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

La-doped SrTiO<inf>3</inf>/TiO<inf>2</inf> (La:STO/TO) eutectic crystals were grown by a micro-pulling-down method at various growth rates to control the eutectic morphology and thermoelectric properties. The La:STO/TO eutectic crystals were composed of a TiO<inf>2</inf> (TO) rod phase in the SrTiO<inf>3</inf> (STO) matrix phase for all growth rates. The diameter of the TO rod phase systematically decreased as the growth rate was increased, according to the Jackson–Hunt model, and the diameter reached approximately 1 μm at a growth rate of 1 mm/min. The La:STO/TO eutectic crystal exhibited a lower thermal conductivity than the Nb:STO single crystal, owing to the decrease in the lattice thermal conductivity by phonon scattering at boundaries in the eutectic morphology. The figures of merit, ZTs, of the La:STO/TO eutectic crystals grown at 0.02 and 0.5 mm/min growth rates were 0.015 and 0.025, respectively. The faster growth rate led to an increased ZT, owing to the decrease in electrical resistivity.

DOI： 10.1016/j.jcrysgro.2022.126551

Web of Science

Scopus

担当区分：責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

La<inf>2</inf>Hf<inf>2</inf>O<inf>7</inf> crystals with a melting point of ∼2418 °C were grown by the micro-pulling-down method using a W crucible and deoxygenated ZrO<inf>2</inf> insulators. A La<inf>2</inf>Hf<inf>2</inf>O<inf>7</inf> crystal grown at a rate of 0.07 mm/min (LHO[0.07 mm/min]) showed a high transparency without any visible cracks and inclusions, while a La<inf>2</inf>Hf<inf>2</inf>O<inf>7</inf> crystal grown at a rate of 2.00 mm/min had some cracks. The LHO[0.07 mm/min] crystal had a transmittance of over 70% in the wavelength range of 450–800 nm. The X-ray rocking curve of the LHO[0.07 mm/min] crystal showed a symmetric sharp peak with a full width at half maximum of 138 arcsec. The Laue image revealed that the grown crystals were single crystals.

DOI： 10.1016/j.jcrysgro.2022.126547

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Crystal Growth  

In this study, Tb:BaCl<inf>2</inf> and NaCl/KCl ternary eutectics were grown using quartz ampoules via the vertical Bridgman–Stockbarger method. Each crystal phase had a polygonal columnar shape with a length of 300 µm along the growth direction. The Tb:BaCl<inf>2</inf> scintillator phase grew in the columnar phase. The BaCl<inf>2</inf> scintillator phase is expected to make optical waveguides of the scintillation light. The expected Tb³⁺ emission peak was observed at approximately 360–630 nm under X-ray irradiation. This emission is mainly attributed to the Tb³⁺⁵D<inf>4</inf>→⁷F<inf>6</inf>, ⁷F<inf>6</inf>, ⁷F<inf>5</inf>, ⁷F<inf>4</inf>, and ⁷F<inf>3</inf> transitions and BaCl<inf>2</inf> host emission transition. The photoluminescence decay times of the Tb:BaCl<inf>2</inf>/NaCl/KCl eutectics was 0.49 ms (7.5%) and 6.64 ms (92.5%).

DOI： 10.1016/j.jcrysgro.2021.126467

Web of Science

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：IEEE Transactions on Ultrasonics Ferroelectrics and Frequency Control  

The effect of the difference in the thickness ratio of the double-layered thickness-shear resonator on the temperature characteristics of the resonance frequency was investigated using a Ca₃TaGa₃Si₂O₁₄ (CTGS) single crystal. Three specimens with thickness ratios of <inline-formula> <tex-math notation="LaTeX">${x} =0.25$ </tex-math></inline-formula>, 0.33, and 0.50 were prepared using <inline-formula> <tex-math notation="LaTeX">$122^{\circ } ~{Y}$ </tex-math></inline-formula>- and <inline-formula> <tex-math notation="LaTeX">$171^{\circ }~{Y}$ </tex-math></inline-formula>-cut CTGS substrates. For the specimens with <inline-formula> <tex-math notation="LaTeX">${x} =0.25$ </tex-math></inline-formula> and 0.33, the temperature characteristics varied depending on the order of the resonance mode. For the specimen with <inline-formula> <tex-math notation="LaTeX">${x} =0.50$ </tex-math></inline-formula>, on the other hand, almost the same temperature characteristics were observed regardless of the order of the resonance mode. To interpret this phenomenon, a new equation for predicting the temperature characteristics of the fundamental mode (first mode) for the double-layered resonator was created using the electric flux density ratio generated in the two substrates. The expected values using this equation were in good agreement with the result of the first mode temperature characteristics.

DOI： 10.1109/TUFFC.2021.3121782

Web of Science

Scopus

PubMed

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記述言語：日本語   会議種別：口頭発表（一般）  

開催地：東北大学川内北キャンパス・オンライン   国名：日本国  

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開催地：オンライン  

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

DOI： 10.19009/jjacg.49-2-00

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

担当区分：筆頭著者,　責任著者   記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

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