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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. [ABSTRACT FROM AUTHOR]

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 3 Al 5 O 12 :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 (σ) of the scintillation light output at each position of the 50-mm-long sample was found to be within ±16%. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [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]

• (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]

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]