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• Mg 2 Si/Si eutectics of 1 in. in diameter were solidified by the VB method at three pulling rates. • The Mg 2 Si/Si eutectics indicated a phase-separated eutectic structure of the Mg 2 Si and Si phases. • The eutectic morphology became finer with an increase in the pulling rate. • The thermal conductivity systematically decreased with an increase in the pulling rate. • The power factor was improved in the temperature ranges above 400 °C compared to the Mg 2 Si. • The ZT value reached 0.076 at 600 °C for the Mg 2 Si/Si solidified at a 103 pulling rate. Mg 2 Si/Si eutectics are grown from melt by the Vertical Bridgman method using a carbon crucible at three pulling rates. All the Mg 2 Si/Si eutectics are composed of Mg 2 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 2 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 2 Si/Si eutectics are larger than those of Mg 2 Si above 400 °C because of the increase in the Seebeck coefficient. The figure of merit, ZT , of the Mg 2 Si/Si eutectics solidified at a 103 mm/min pulling rate reached 0.076 at 600 °C. [ABSTRACT FROM AUTHOR]

In this study, charge compensation was performed by co-doping Na + ions at the Ca2+ sites of Ce-doped LiCaAlF 6 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 3 significantly increased the effective segregation coefficient k eff of the Eu2+ ions in Eu-doped LiCaAlF 6 and Eu-doped LiSrAlF 6 single crystals. The Al metal and EuF 3 in the starting materials produced EuF 2 via a chemical reaction, and the Eu2+ ions in EuF 2 could be substituted at the Ca2+ and Sr2+ sites. In addition, the Ca/Sr ratio control of the Li(Ca,Sr)AlF 6 :Eu solid-solution scintillator single crystals improved the light yield through band-gap control, and the Li(Ca,Sr)AlF 6 :Eu single crystal with a 25% Sr concentration exhibited the highest light yield. Charge compensation was conducted using Na co-doping to improve the radiation resistance of the LiCAF:Ce single crystals, thereby preventing the generation of cation defects by the Ce3+-doping at the Ca2+ site. It was determined that the improvement in the radiation resistance of the LiCAF:Ce single crystal via Na co-doping can contribute to the improvement in the durability of the production of LiCAF:Ce single crystals. [Display omitted] • Scintillation properties of LiCaAlF 6 and LiSrAlF 6 single crystals were improved by chemical composition control. • Charge compensation by Na co-doping for LiCAF:Ce single crystals prevents generations of cation vacancies by Ce3+-doping. • Al metal greatly increases the segregation coefficient of Eu ion in the LiCAF and LiSAF single crystals. • Effective segregation coefficient of Eu2%,AlM1%:LiSrAlF 6 crystal was improved to 0.986 using the Al metal. • Ca/Sr ratio control in the Eu:Li(Ca,Sr)AlF 6 single crystals improves the light yield under thermal neutron irradiation. [ABSTRACT FROM AUTHOR]

• La-doped SrTiO 3 /TiO 2 eutectic crystals were grown by a micro-pulling-down method. • Grown crystals were composed of the TiO 2 rod phase in the SrTiO 3 matrix phase. • Diameter of TiO 2 rods systematically decreased as the growth rate was increased. • Grown crystal exhibited a lower thermal conductivity than the SrTiO 3 single crystal. • ZT s of crystals grown at 0.02 and 0.5 mm/min were 0.015 and 0.025, respectively. La-doped SrTiO 3 /TiO 2 (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 2 (TO) rod phase in the SrTiO 3 (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, ZT s, 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. [ABSTRACT FROM AUTHOR]

• La 2 Hf 2 O 7 crystals (m.p.: 2418 °C) were grown by the µ-PD method using a W crucible. • The La 2 Hf 2 O 7 grown at a rate of 2.00 mm/min had some cracks. • The La 2 Hf 2 O 7 grown at a rate of 0.07 mm/min was transparent without any cracks. • The LHO[0.07 mm/min] had a transmittance of over 70% in the range of 450–800 nm. • The XRC of the LHO[0.07 mm/min] showed a sharp peak with a FWHM of 138 arcsec. La 2 Hf 2 O 7 crystals with a melting point of ∼2418 °C were grown by the micro-pulling-down method using a W crucible and deoxygenated ZrO 2 insulators. A La 2 Hf 2 O 7 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 2 Hf 2 O 7 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. [ABSTRACT FROM AUTHOR]

• La 2 Zr 2 O 7 crystals were grown by micro-pulling-down method using Mo & W crucibles. • Grown crystals under Ar + 3%H 2 were composed of La 2 Zr 2 O 7 phase including Mo and W. • A grown crystal under Ar using W crucible & deoxygenated insulator was La 2 Zr 2 O 7. • The La 2 Zr 2 O 7 crystal indicated a transmittance exceeding 70% after post-annealing. La 2 Zr 2 O 7 crystals with a melting point of 2283 °C are grown via the micro-pulling-down (μ-PD) method using Mo and W crucibles to expand the possibility of material research of functional single crystals with high melting points by the μ-PD method. La 2 Zr 2 O 7 crystals grown using Mo and W crucibles under an Ar + 3% H 2 atmosphere are composed of a La 2 Zr 2 O 7 main phase, which includes Mo and W. However, a La 2 Zr 2 O 7 crystal without W can be grown under an Ar atmosphere using the μ-PD method using a W crucible and deoxygenated ZrO 2 insulators. After post-annealing in air at 1000 °C, the La 2 Zr 2 O 7 crystal without W becomes colorless and transparent, indicating a transmittance exceeding 70% in wavelengths ranging from 450 to 800 nm. [ABSTRACT FROM AUTHOR]

We have successfully grown single crystals of layered mixed-anion compound Sr 2 ZnCu 2 Se 2 O 2 by a simple melt-growth method. Single crystals of the layered oxychalcogenides Sr 2 ZnCu 2 Se 2 O 2 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 (00 12) 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 2 ZnCu 2 Se 2 O 2 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. [ABSTRACT FROM AUTHOR]

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 ${x} =0.25$ , 0.33, and 0.50 were prepared using $122^{\circ } ~{Y}$ - and $171^{\circ }~{Y}$ -cut CTGS substrates. For the specimens with ${x} =0.25$ and 0.33, the temperature characteristics varied depending on the order of the resonance mode. For the specimen with ${x} =0.50$ , 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. [ABSTRACT FROM AUTHOR]

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 2 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 2 crystal structure and Eu2+ 5d–4f luminescence were maintained. The γ-ray responses, such as light yield and decay time, were also investigated. [ABSTRACT FROM AUTHOR]

• (Gd 1-x Ce x) 3 (Ga 0.995 Cr 0.005) 5 O 12 single crystals were grown by micro-pulling down method. • The emission wavelengths of these crystals were approximately 730 nm. • Cr was segregated in the center part of the crystals. • The relationship between Cr segregation and emission intensity was investigated. • The correlation coefficients of thoes relationships were around 0.9. 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 3 Ga 5 O 12 (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. [ABSTRACT FROM AUTHOR]

• Phase diagram for the CsI-LiBr binary system established. • Vertical Bridgman method employed for crystal growth. • Homogeneous eutectic crystals obtained. • Light yield (thermal neutron irradiation) was 6.7 times higher than that of the LiCAF. • This helps development of eutectic scintillators with improved crystal structure. 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. [ABSTRACT FROM AUTHOR]

The pure and strontium (Sr) substituted LaFeO 3 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 3 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 3 crystal. A colossal dielectric behavior and electrical conductivities were analyzed through dielectric studies. The activation energies of pure and Sr substituted LaFeO 3 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 3 crystal was discussed with Zero field cooled (ZFC) and Field cooled (FC) modes for its potential magnetic application. • Peak shift of (121) plane confirms the lanthanide contraction in Sr substituted LaFeO 3 • At 742 K, Sr substituted LaFeO 3 crystal show enhanced dielectric constant, ɛ r = 3.25 × 105 • Ea value of LaFeO 3 and LaSrFeO 3 are 0.19 and 0.16 eV respectively • Sr substituted LaFeO 3 exhibits anti-ferro to ferromagnetic phase transition at 135 K • Sr substituted LaFeO 3 crystal shows improved coercivity, H c = 748.8164 Oe [ABSTRACT FROM AUTHOR]

• Ce doped LaCl 3 /AECl 2 (AE = Mg, Ca, Sr) eutectics were grown by BS method. • In case of AE = Mg, Ca, eutectic with PSSFs structures were observed. • The Ce:LaCl 3 /CaCl 2 eutectic showed Ce3+ 4f-5d emission at 345 nm. • The light output of Ce:LaCl 3 /CaCl 2 under 137Cs was 9000 photons/MeV. • The scintillation decay time under 137Cs was 26.8 ns (26%) and 282 ns (74%). Ce-doped LaCl 3 /AECl 2 (AE = Mg, Ca, Sr) system eutectics were explored. Ce-doped LaCl 3 / AECl 2 (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 0.708 Sr 0.292 Cl 2.708 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 3 /CaCl 2 eutectic showed 345 nm emission ascribed to Ce3+ 4f-5d transition under X-ray excitation. The Ce:LaCl 3 /CaCl 2 sample resulted in the highest light output of 9,000 photon/MeV, which is comparable to the previously reported eutectic scintillator Ce:GdAlO 3 /α-Al 2 O 3 , 9500 photon/MeV. Scintillation decay time of the Ce:LaCl 3 /CaCl 2 sample under 662 keV gamma-ray excitation was 26.8 ns (26%) and 282 ns (74%). [ABSTRACT FROM AUTHOR]

In this study, Ce:6LiBr/LaBr 3 eutectic with a high Li concentration was developed as a novel thermal neutron scintillator. Ce served as an activator for the LaBr 3 phase, and Ce:6LiBr/LaBr 3 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 3 worked as the scintillator phase. The Ce:6LiBr/LaBr 3 eutectic exhibited a lamellar eutectic structure and optical transparency, as well as 350 and 380 nm emission due to Ce 3 + 5d-4f transition. The light yield under neutrons excitation was estimated to be 74000 photons/neutron. The scintillation decay time was 18.7 ns. • Optically semitransparent Ce-doped 6LiBr/LaBr 3 eutectic was grown. • The vertical Bridgman–Stockbarger (VB) method enables unidirectional solidification to grow the directionally solidified eutectic (DSE). • Ce 3 + emission peaks at 350 and 380 nm were observed in the LaBr 3 phase. • Scintillation decay time under 252Cf neutron excitation was 18.7 ns. • The light yield under 252Cf neutron excitation was around 74000 photon/neutron. [ABSTRACT FROM AUTHOR]

• A novel ternary Tb:BaCl 2 /NaCl/KCl eutectic scintillator is reported. • Directionally solidified eutectic was grown by the VB method. • Columnar BaCl 2 fibres with a length of 300 μm were obtained at a growth rate of 0.01 mm/min. • The expected Tb3+ emission was observed only in the BaCl 2 phase. • The decay times of the eutectic were 0.49 ms (7.5%) and 6.64 ms (92.5%) In this study, Tb:BaCl 2 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 2 scintillator phase grew in the columnar phase. The BaCl 2 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 4 →7F 6, 7F 6 , 7F 5 , 7F 4 , and 7F 3 transitions and BaCl 2 host emission transition. The photoluminescence decay times of the Tb:BaCl 2 /NaCl/KCl eutectics was 0.49 ms (7.5%) and 6.64 ms (92.5%). [ABSTRACT FROM AUTHOR]

• A novel ternary CsI/KI/KCl eutectic scintillator is reported. • Directionally solidified eutectic was grown using the Bridgman–Stockbarger method. • The expected Tl+ emission peak near 486 nm was observed in the CsI phase. • The decay time of the eutectic was 313 ns. • The light output of the eutectic was approximately 22,000 photons/MeV. In this study, Tl:CsI/KI/KCl eutectic scintillators were grown using the Bridgman–Stockbarger method by unidirectional solidification. The eutectic phases were uniformly distributed in the transverse direction and were slightly aligned along the growth direction. The Tl:CsI scintillator phase was grown as a matrix, which was then used for creating optical waveguides of the scintillation light. The expected Tl+ emission peak was observed at 486 nm under X-ray excitation and cathodoluminescence; this was attributed to the self-trapped exciton perturbed by TI+ in Tl:CsI. The decay time of the Tl:CsI/KI/KCl eutectic was 313 ns, and its light output was estimated to be 22,000 photons/MeV. [ABSTRACT FROM AUTHOR]

• (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 single crystal was grown by the micro-pulling-down method. • Quenching temperature of (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 was determined to be 526 K. • Light output of (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 was determined to be ~12,000 photons/MeV. We have grown Ce-doped (La,Y) 2 Si 2 O 7 single crystal by micro-pulling-down method and investigated its optical and scintillation properties. We have successfully prepared the single crystal with (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 composition. The observed thermal quenching process could be characterized by the quenching temperature (T 50%) of 526 K and its activation energy was determined to be 0.62 eV. Further considering the thermal quenching factors, it was found that the thermal quenching was caused by at least the thermal ionization and maybe also by classical thermal quenching. The light output and scintillation decay time were evaluated to be ~12,000 photons/MeV and ~42 ns, respectively. These results indicate that (Ce 0.015 La 0.600 Y 0.385) 2 Si 2 O 7 has a great potential for application in scintillation materials. [ABSTRACT FROM AUTHOR]