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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]

Al concentration dependence of the crystal structure on Ca 3 Ta(Ga 1- x Al x)Si 2 O 14 (CTGAS) piezoelectric single crystals were investigated by X-ray crystal structure analysis. O(2)-Si-O(2) and Si-O(2)-(Ga,Al) bond angles systematically increased with increasing Al concentration, and the result suggests that the increase of structural anisotropy by the Al substitution is attributable to the planarization of the O(2)-Si-O(2)-(Ga,Al). In addition, (Ga,Al)-O(2), (Ga,Al)-O(3) and Ca-O(1) bond lengths systematically decreased with increasing the Al substitution. The cation shift of the Si and (Ga,Al) ions out of center from the barycenter of the oxygen coordination environment decreased with increasing Al concentration. Image 1 [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]

Abstract Ce:(Gd,La) 2 Si 2 O 7 (Ce:La-GPS) and Al co-doped Ce:(Gd,La) 2 Si 2 O 7 (Al,Ce:La-GPS) single crystals were grown by the micro-pulling-down method to improve the mechanical, optical and scintillation properties. In a tensile test, the maximum strain and stress values in the stress-strain curve of the Al,Ce:La-GPS single crystal compared to the Ce:La-GPS single crystal and the result suggests that there is a possibility of the improvement on the mechanical property by Al co-doping. In addition, the light yield of the La-GPS single crystal under γ-ray irradiation was slightly increased and the decay time was accelerated by the Al co-doping. Highlights • Al co-doped Ce:La-GPS single crystals were grown by the μ-PD method. • It is a possibility that Al co-doping improves the mechanical property of the La-GPS. • Emission peaks originated from 5 d-4f transitions of the Ce3+ ion were observed. • The light yield under γ-ray irradiation was slightly increased by Al co-doping. • Scintillation decay times were accelerated by Al co-doping. [ABSTRACT FROM AUTHOR]

Eu-doped Li(Ca,Sr)AlF 6 [Eu:LiCSAF] single crystals with various Ca/Sr ratios were grown by the micro-pulling-down method, and their optical and scintillation properties were investigated to reveal the effects of Ca/Sr ratio on optical and scintillation properties of the Eu:LiCSAF single crystals. The Li(Ca 1− x − y Sr x Eu y )AlF 6 single crystals could be grown in 0 ≤  x  ≤ 0.1, 0.5 ≤  x  ≤ 1.0 and y  = 0.02 while the Eu:LiCSAF crystals with x  = 0.2, 0.25 and 0.4 included two colquiriite-type phases with different lattice parameters. The Li(Ca 1− x−y Sr x Eu y )AlF 6 single crystal with x  = 0.25 and y  = 0.02 showed the highest light yield under neutron irradiation. [ABSTRACT FROM AUTHOR]

Pr-doped SrI 2 (Pr:SrI 2 ) single crystals with various Pr concentrations were grown by the halide-micro-pulling-down (H-μ-PD) method, and the scintillation properties were investigated. Pr1%:SrI 2 single crystal with high transparency could be grown by the H-μ-PD method while Pr2, 3 and 5%:SrI 2 single crystals included some cracks and opaque parts. In the photoluminescence spectrum of the Pr1%:SrI 2 single crystal, an emission peak originated from the Pr 3+ ion was observed around 435 nm while the radioluminescence spectra showed an emission peak around 535 nm for the undoped SrI 2 and Pr:SrI 2 single crystals. Light yields of Pr1, 2, 3 and 5%:SrI 2 single crystals under γ-ray irradiation were 7700, 8700, 7200 and 6700 photons/MeV, respectively. Decay times of Pr1 and 2%:SrI 2 single crystals under γ-ray irradiation were 55.9 and 35.0 ns of the fast decay component, and 435 and 408 ns of the slow decay component, respectively. [ABSTRACT FROM AUTHOR]

Ca 3 Ta(Ga 0.9 Sc 0.1 ) 3 Si 2 O 14 langasite-type single crystal with a diameter of 1 in. was grown by Czochralski (Cz) method. Obtained crystal had good crystallinity and its lattice constants exceeded those of Ca 3 TaGa 3 Si 2 O 14 (CTGS) according to the X-ray analysis. A crack-free specimen cut from the grown crystal was used for the measurements of dielectric constant ε 11 T / ε 0 , electromechanical coupling factor k 12 , and piezoelectric constant d 11 . The accuracies of these measurements were better than those for the crystal grown by micro-pulling-down (μ-PD) method. Substitution of Ga with Sc resulted modification of these constants in the directions opposite to those observed after partial substitution of Ga (of CTGS) with Al. This suggests that increase of | d 14 | was most probably associated with enlargement of average size of the Ga sites. The crystal reported here had greater dimensions as compared to analogous crystals grown by the μ-PD method. As a result, accuracy of determination of acoustic constants of this material may be improved. [ABSTRACT FROM AUTHOR]

Melt growth of scintillating halide crystals is reviewed. The vertical Bridgman growth technique is still considered as very popular method that enables production of relatively large and commercially attractive crystals. On the other hand, the micro-pulling-down method is preferable when fabrication of small samples, sufficient for preliminary characterization of their optical and/or scintillation performance, is required. Moreover, bulk crystal growth is also available using the micro-pulling-down furnace. The examples of growths of various halide crystals by industrially friendly melt growth techniques including Czochralski and edge-defined film-fed growth methods are also discussed. Finally, traveling molten zone growth that in some degree corresponds to horizontal zone melting is briefly overviewed. [ABSTRACT FROM AUTHOR]

Two iridium crucibles with one and five capillaries at a nozzle were developed for the growth of Ce-doped Y 3 Al 5 O 12 [Ce:YAG] single crystals by the micro-pulling-down [μ-PD] method. The purpose of the study was to examine the effect of the capillary number on the Ce distribution in the radial direction of the crystals. The crystals grown from 2 mol% and 5 mol% Ce-doped YAG melts were then cut perpendicular to the growth direction and polished to produce specimens suitable for the measurement of Ce distribution. The Ce:YAG crystals grown using the crucible with one capillary [Ce:YAG(1 C)] had greater Ce content in the central portion of the crystal when compared to its peripheral parts. On the other hand, in the case of the Ce:YAG crystal grown using the crucible with five capillaries [Ce:YAG(5 C)], the increased Ce concentration was detected in five specimen sections positioned just below the capillaries. The results indicated that increase of the number of capillaries is effective practice that results in an improvement of the radial homogeneity of the single crystals grown by the μ-PD method. [ABSTRACT FROM AUTHOR]

Platinum (Pt) crystalline fibers were grown from the melt by the micro-pulling-down (μ-PD) method using the ZrO 2 ceramics crucible. The diameter of the grown Pt fiber was controlled by the ϕ1 mm outlet made at the bottom of the crucible and the Pt fiber of 0.95±0.03 mm in diameter and over 5 m in length was obtained at 10 mm/min pulling-down rate. In addition, the Pt fiber was grown at 1–110 mm/min pulling rates while the liquid-solid interface reached the bottom of the crucible and the crystal growth became unstable at 120 mm/min pulling rate. Few grain boundaries were observed in the scanning electron microscopy image of the Pt fibers and there were some spots with high intensity in the pole figures. [ABSTRACT FROM AUTHOR]

Ca 3 Ta(Ga 1- x Al x ) 3 Si 2 O 14 [CTGAS] material is a piezoelectric material belonging to the Langasite-type group (space group: P321).and the CTGAS single crystals ( x =0, 0.25, 0.50, 0.75) with a diameter of 1 in. were grown by a Czochralski [Cz] method using an Ir crucible under Ar+2%O 2 . The CTGAS single crystals without any cracks could be grown using a CTGAS seed crystal in the x range of 0≤ x ≤0.75. Cell parameters, a and c , decrease while the a / c ratio increased with the Al concentration. Piezoelectric constant d 11 and electromechanical coupling factor k 12 for the X-cut specimens of the CTGAS single crystals were increased by the Al substitution. [ABSTRACT FROM AUTHOR]

Na co-doped Eu: LiCaAlF 6 (Eu, Na: LiCAF) single crystals were grown by the micro-pulling-down (μ-PD) method, and their optical and scintillation properties were examined to reveal the effects of the Na co-doping. The crystals were single-phase materials demonstrating structure isomorphic with that of undoped LiCAF. To perform the crystals characterization, the specimens with dimensions of several millimeters were cut from highly transparent and crack free fragments of the crystals and polished. It was observed that Na co-doping resulted modification of the transmittance and the excitation spectra, and increased the light yield detected under neutron irradiation. [ABSTRACT FROM AUTHOR]

We developed the growth technique of the CeBr3 scintillator single crystal by a Halide-micro-pulling-down (H-μ-PD) method using a carbon crucible with a die under suitable temperature gradient. Four-types after-heaters with different configurations were prepared to control the temperature gradient around the liquid-solid interface during crystal growth. The high temperature gradient resulted in the stable meniscus during the crystal growth and the CeBr3 single crystal with high transparency could be obtained. The light yield and the decay time under γ-ray irradiation were ∼68,000 ph/MeV and 19 ns, respectively. [ABSTRACT FROM AUTHOR]

The In-doped LiCaAlF 6 [In:LiCAF] single crystals were grown by the micro-pulling-down (μ-PD) method, and the phases, chemical compositions, transmittance and radioluminescence spectra were investigated. All the grown crystals showed high transparency and single phase of LiCAF without visible cracks and inclusions except for the end part of In2%:LiCAF crystal which included the impurity phase. In the radioluminescence spectra of the In:LiCAF crystals under X-ray irradiation, the emission peak around 750 nm was revealed. [ABSTRACT FROM AUTHOR]

We developed novel growth methods for halide scintillator single crystals with hygroscopic nature, Halide micro-pulling-down [H-μ-PD] method and Halide Vertical Bridgman [H-VB] method. The H-μ-PD method with a removable chamber system can grow a single crystal of halide scintillator material with hygroscopicity at faster growth rate than the conventional methods. On the other hand, the H-VB method can grow a large bulk single crystal of halide scintillator without a quartz ampule. CeCl 3 , LaBr 3 , Ce:LaBr 3 and Eu:SrI 2 fiber single crystals could be grown by the H-μ-PD method and Eu:SrI 2 bulk single crystals of 1 and 1.5 inch in diameter could be grown by the H-VB method. The grown fiber and bulk single crystals showed comparable scintillation properties to the previous reports using the conventional methods. [ABSTRACT FROM AUTHOR]

We grew Lu-substituted CeBr 3 [(Ce 1− x Lu x )Br 3 ] crystals by a modified micro-pulling-down method to increase the effective atomic number and to investigate effects of the Lu substitution on the crystal growth, phase generation, chemical composition, and optical and scintillation properties. The (Ce 1− x Lu x )Br 3 crystals with x =0 and 0.01 had high transparency while the milky parts were generated in the crystals with x =0.05 and 0.20. By the analysis of chemical composition, the estimated Z eff increased to 47.9. On the other hand, the light yields were systematically decreased and decay times were increased with increasing Lu concentration. [ABSTRACT FROM AUTHOR]

A shape-controlled Ce doped Y 3 Al 5 O 12 (Ce:YAG) single crystal has been grown by a micro-pulling-down method using an Ir crucible with a square die. The as-grown Ce:YAG single crystal has square-shape and flat surfaces with high transparency. The shape-controlled Ce:YAG single crystal showed more than 70% transmittance from 530 nm to 900 nm without any cutting and polishing. An emission peak around 540 nm was observed in the radioluminescence spectrum under X-ray irradiation. In addition, the light yield and energy resolution under γ-ray irradiation of the as-grown crystal without any cutting and polishing were approximately 23,000 pH/MeV and 16%, respectively. [ABSTRACT FROM AUTHOR]

Acoustically related physical constants were experimentally determined for Ca3Nb(Ga0.75Al0.25)3Si2O14 (CNGAS) single crystal for the first time. Several plate specimens of the X-, Y -, Z -, 40.24 ^\circ Y -, and 144.98 ^\circ Y -cut were prepared from a CNGAS single crystal ingot grown by Czochralski technique. Elastic constants, piezoelectric constants, and their temperature coefficients for CNGAS were determined from longitudinal wave and shear wave velocities at around room temperature, measured by the ultrasonic microspectroscopy system. Dielectric constants, density, and coefficients of thermal expansion were also measured. It was demonstrated that the determined constants could provide calculation accuracy within ±0.12% in leaky surface acoustic wave velocity. The piezoelectric constants for CNGAS were a 7.2% increase in e11 and a 1.7% decrease in e14 due to Al-substitution effect, compared with those of Ca3NbGa3Si2O14. The appropriate cut angle for thickness-shear mode resonator with zero temperature coefficient of velocity was estimated to be around 150 ^\circ Y -cut from calculations using the determined constants of CNGAS exhibiting electromechanical coupling factor k^2 of 3.19% and power flow angle of −1.70°. [ABSTRACT FROM AUTHOR]

The ns 2 -type metal elements (Pb and Sn) doped LiCaAlF 6 single crystals were grown by a micro-pulling-down (μ-PD) method. Pb doped LiCaAlF 6 [Pb:LiCAF] crystals showed high transparency and single phase of the LiCAF structure. However, we could not obtain Sn:LiCAF crystals due to the evaporation of SnF 2 during the crystal growth. There was an absorption peak around 193 nm in the transmittance spectrum of Pb:LiCAF crystal. In the radioluminescence spectrum of the Pb:LiCAF crystal under X-ray irradiation, two emission peaks around 200 and 830 nm were observed. [ABSTRACT FROM AUTHOR]

We grew Na and K co-doped Eu:SrI 2 [Na,Eu:SrI 2 and K,Eu:SrI 2 ] crystals by a modified micro-pulling-down method to reveal the co-doping effects on the crystal growth and scintillation properties. The non-codoped, Na0.5%, Na1.0%, K0.5% and K1.0%,Eu:SrI 2 crystals indicated high transparency while the milky parts were generated in the Na5.0% and K5.0%,Eu:SrI 2 crystals. The light yields of Na,Eu:SrI 2 and K,Eu:SrI 2 crystals under γ-ray irradiation were decreased by the Na and K co-doping. On the other hand, there was a small change within 940–1020 ns in the decay times by the Na and K co-doping. In the light yield proportionality under γ-ray irradiation, the non-proportionality in the low energy region was improved by Na and K co-doping. [ABSTRACT FROM AUTHOR]

Optical and scintillation properties of Sr 3 NbGa 3 Si 2 O 14 [SNGS] and Sr 3 TaGa 3 Si 2 O 14 [STGS] single crystals with the langasite-type crystal structure were investigated as a novel scintillator materials. In the transmittance spectra of the SNGS and STGS polished specimens, absorption peaks around 380 and 505 nm were observed and the absorptions are considered to be attributable to the excess oxygen in the crystals. An emission peak around 420 nm was observed in the X-ray radioluminescence spectrum of the SNGS crystal. On the other hand, there was an emission peak around 335 nm in the X-ray radioluminescence spectrum of the STGS crystal. [ABSTRACT FROM AUTHOR]

We grew 1.5-in Eu doped SrI2 (Eu:SrI2) bulk single crystal by a modified vertical Bridgman (VB) method using a removable chamber and high-frequency induction heating. As-grown 1.5-in Eu:SrI2 bulk single crystal had no visible crack and inclusion in the crystal. In the transmittance and $\alpha $-ray radioluminescence spectra, large absorption below 433 nm and emission peak at 433 nm were observed, respectively. Each polished 56 \thinspace 000 \sim 62 \thinspace 000\ \ph/MeV light yield and 3.3 \sim 3.9\%$ energy resolution. The decay times of the specimens were 0.61 \sim 0.67\ \mu \s. [ABSTRACT FROM AUTHOR]

Eu doped SrI 2 (Eu:SrI 2 ) single crystals with various Eu contents were grown by a modified micro-pulling-down (μ-PD) method and effects of Eu concentration on scintillation properties were investigated. Eu 1%, 5%, 7.5%, 10% and 15%:SrI 2 single crystals were obtained and all as-grown crystals indicated high transparency without visible inclusion. Actual Eu contents in the grown crystals were almost same as nominal compositions. In the X-ray radioluminescence spectra, emission peaks around 435 nm were observed in all crystals. Eu7.5 mol%:SrI 2 crystals indicated the highest light yield, 78,000 ph/MeV, and the smallest energy resolution, 3.7%. [ABSTRACT FROM AUTHOR]

Sr co-doped Ce:LiCaAlF 6 [Ce:Li(Ca,Sr)AlF 6 ] crystals with various Ca/Sr ratios were grown by a micro-pulling-down (μ-PD) method and effects of Sr co-doping on crystal structure, chemical composition, optical and scintillation properties for Ce:LiCaAlF 6 crystals were investigated as a neutron scintillator. High transparent Ce2%:Li(Ca,Sr)AlF 6 crystals with 2% and 5% Sr contents were obtained while Ce2%:Li(Ca,Sr)AlF 6 crystals with 10% and 20% Sr contents included milky parts in the crystals. a - and c -axis lengths of Ce:Li(Ca,Sr)AlF 6 phase systematically increased with an increase of Sr content. In addition to the emission at 284 and 308 nm from Ce 3+ ion, emission peaks at 367 nm appeared by Sr co-doping. [ABSTRACT FROM AUTHOR]

Abstract: Undoped and 0.5mol% Ce-doped LiF–LiYF4 eutectic crystals were grown by the micro-pulling-down method at different growth rates. The SEM images of all the eutectic crystals showed LiF with rod-like structure in the LiYF4 matrix. The diameter of the rod phase systematically decreased with the increase of the growth rate. The radioluminescence spectra of cerium doped crystal under alpha-ray excitation showed emission peak at 325nm related to Ce3+ 5d-4f transition. The white part in the cathodoluminescence image is considered to be due to Ce3+ ion in LiYF4 phase, according to the scanning electron microscopy (SEM) image in the same region. [Copyright &y& Elsevier]

Abstract: The undoped and Ce-doped LiF/LiLuF4 eutectic fibers with various ratios of LuF3 to LiF were grown by the micro-pulling-down method for their application as neutron scintillators with light guiding structure. The differential thermal analysis (DTA) of undoped eutectic materials indicated that the eutectic point of LiF/LiLuF4 was positioned around LiF 80mol%–LuF3 20mol% composition. Some of the as-produced eutectic solids had rod-like regular array structures. This was observed using SEM images of cross-sectional and parallel cuts of the grown solids. In the range of x ≥0.28, the dendrites appeared between the eutectic areas. Ce doped LiF/LiLuF4 eutectic fibers demonstrated two emission peaks around 310 and 326nm in the photoluminescence spectrum, and the decay time of the emission at 326nm was 32.3ns. [Copyright &y& Elsevier]

• 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]

Abstract: We have investigated the optical properties of 1mol% Nd-doped SrBr2 crystal grown by the Bridgman technique for an X-ray scintillator application. We succeeded in obtaining a transparent crystal, whose X-ray diffraction was measured under dry condition because of its hygroscopic nature. Roughly, we estimated that 90% of this crystal dissolved within 300min. under 25°C and 65–70% humidity. Under excitation by 270 and 400nm photons several emission peaks originating from 4F3/2 or 4G i1→4I i2 (i1=5/2 and 7/2 and i2=13/2, 11/2, and 9/2) transitions of Nd3+ were observed. 1mol% Nd:SrBr2 had a maximum quantum yield of approximately 45%. Additional emission peaks were observed under X-ray excitation. [Copyright &y& Elsevier]

Abstract: We have investigated the optical and scintillating properties of Lu co-doped Ce:LiYF4 single crystals with various Lu content. In the transmittance and absorption spectra, the absorption peaks at 243 nm get systematically red shifted in contrast to the peaks at 197 and 200 nm which get blue shifted with the increase in Lu content. At the same time, emission peaks at 306 nm and 200 nm under 295 nm excitation also get red shifted. The decay time of Ce:Li(Y,Lu)F4 crystals under 295 nm excitation is found to be faster than that of Ce:LiYF4 and Ce:LiLuF4 crystals. The alpha-peak positions in the pulse-height spectra and decay times of crystals under alpha-ray irradiation are found to vary with the Lu content. [Copyright &y& Elsevier]

Ba co-doped Ce:LiCaAlF{{6}} [Ce:Li(Ca,Ba)AlF{{6}}] and LiCaAlF{{6}} [Li(Ca,Ba)AlF{{6}}] crystals with various Ba concentrations were grown and their structures, optical and scintillation properties were investigated. As-grown Ce2%Ba1% and Ce2%Ba2%:Li(Ca,Ba)AlF{{6}} crystals were high transparency in all parts while an end part of as-grown Ce2%Ba5%:Li(Ca,Ba)AlF{{6}} crystal and all parts of as-grown Ba5%:Li(Ca,Ba)AlF{{6}} crystal included milky parts which decreased transmittance. Ce:Li(Ca,Ba)AlF{{6}} crystals indicated the emission peaks at 288 and 308 nm from which was attributable to the 5d-4f transition of Ce^3+ ion in the radioluminescence spectra under \alpha-ray irradiation. In the case of Ce1%Ba2%:Li(Ca,Ba)AlF{{6}} crystal, light yield under thermal neutron irradiation were improved. Decay times of Ce:Ce:Li(Ca,Ba)AlF{{6}} under thermal neutron irradiation systematically increased with an increase of Ba concentration. [ABSTRACT FROM PUBLISHER]

Al substituted Ca3NbGa3Si2O14with various Al concentrations were grown by using micro-pulling-down method and investigate the structure phase, chemical compositions and physical property were investigated. [ABSTRACT FROM PUBLISHER]

The langasite-type Ca3NbGa3Si2O14[CNGS] piezoelectric crystals grown in Air and Ar were annealed under various temperatures and atmospheres and the effects of annealing on various properties were investigated. The absorption peaks around 360 and 500 nm of CNGS crystals grown in Air decreased by the annealing at 1300°C in Ar. On the other hand, the annealing at 1300°C in Air decreased transmittance in the range from 300 to 500 nm for the CNGS crystal grown in Ar. The results suggest that the absorptions around 350 and 500 nm originate from the excess oxygen and the post-annealing can control the oxygen content in the crystals. [ABSTRACT FROM AUTHOR]

Abstract: Column-shaped Ca3TaGa3Si2O14 (CTGS) and plate-like Ca3NbGa3Si2O14 (CNGS) single crystals were grown by micro-pulling-down method using crucibles of original shape. The column-shaped CTGS crystals oriented along a- and c-axes were produced using the seeds of corresponding orientations. The plate-like CNGS crystal was grown along a-axis from the crucible equipped with a plate-shaped die at the bottom. The X-ray diffraction patterns of the grown CTGS and CNGS crystals corresponded to langasite-type structure and the lattice parameters were consistent with those of the crystals grown by Czochralski (Cz) method. The X-ray rocking curve analysis indicated that structural perfection of the grown CTGS and CNGS shaped crystals was comparable to that of the crystals produced by Cz method. The central part of the CTGS crystal was single phase material and had excess of Ca and Si with corresponding deficit of Ta and Ga. However, peripheral parts of the crystal contained secondary phase of calcium tantalate. In the transmission spectrum, two broad absorption peaks around 360 and 490nm were observed that was associated with the color centers relevant to the oxygen content in the crystal. [Copyright &y& Elsevier]

Abstract: PbF2 crystal has favorable properties such as a high density and short radiation length, while the scintillation light output is too small to obtain a photo-absorption peak under gamma ray excitation. In this paper, we report scintillation response for 0.1 or 0.5-mol% Ce, Eu and Ho doped PbF2 crystals grown by an annealing method under 5.5-MeV alpha ray excitation. Although Ce doped PbF2 crystals did not show intense photo- and radio-luminescence, Eu and Ho doped ones showed several peaks excited under UV and 5.5-MeV alpha ray excitation, respectively. Additionally, full-absorption peaks in the pulse height spectra of 0.1-mol% Eu and Ho doped PbF2 were ascribed to 5.5-MeV alpha-rays. [Copyright &y& Elsevier]

• 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]

Abstract: Undoped and Eu doped SrI2 (Eu:SrI2) single crystals were grown by the modified micro-pulling-down (μ-PD) method and their scintillation properties were investigated. Undoped and Eu:SrI2 single crystals with Eu 1%, 2%, 3% and 5% concentrations were obtained by the modified μ-PD method with the removable chamber system and their crystals with approximately 2mm diameter and 2–3cm length indicated high transparency. Powder X-ray diffraction patterns of grown Eu:SrI2 crystals revealed that the Eu:SrI2 crystals had a single phase of SrI2 structure and similar lattice parameters regardless of Eu concentrations. In the X-ray radioluminescence spectrum of Eu:SrI2 crystal, the emission peak around 430nm which was due to the 5d–4f transition of Eu2+ ion was observed. Light yields, energy resolutions and decay times of grown Eu:SrI2 crystals irradiated under γ-ray were evaluated. [Copyright &y& Elsevier]

Ca3NbGa3Si2O14(CNGS) single crystals were grown by the micro-pulling-down (μ-PD) method under various atmosphere, Air, Ar + 3%O2and Ar 100%, and the effects of growth atmosphere on crystal growth and optical properties were investigated. While the CNGS crystal grown in Air indicated orange color, the crystal grown in Ar was colorless. CNGS crystal grown in Air indicated several large absorption peaks around 360 and 500 nm in the transmittance spectrum. In contrast, the crystal grown in Ar didn't indicate these absorption peaks. [ABSTRACT FROM AUTHOR]

Abstract: Lu co-doped Ce:LiYF4 single crystals with Lu 0, 25, 50, 75 and 100at% concentrations were grown for the control of mean ionic radius at Y site and the effects on crystal growth, structural phase, crystallinity and segregation were investigated. Lu co-doped Ce 2at%:LiYF4 single crystals with Lu 0, 25, 50, 75 and 100at% concentrations were grown by the micro-pulling-down method and while the initial part of Ce:LiYF4 single crystal indicated opaque and milky due to the increase of mean ionic radius at Y site by Ce3+ doping, Lu co-doped crystals had transparency in all part of crystals. All Lu co-doped crystals indicated a single phase in XRD measurements and the lattice parameters were systematically decreased with an increase in Lu concentration. Crystallinity of grown crystals became worse by Lu co-doping and the effective segregation coefficients of Ce3+ ion for Lu co-doped crystals were almost the same, 0.15–0.19. [Copyright &y& Elsevier]

Ce 2% doped LiYF4 [Ce:LYF] bulk single crystal was grown by Czochralski method and the structural phase, crystallinity, optical properties and scintillation properties were investigated. Grown Ce:LYF bulk single crystal included some cracks in the initial part of crystal and meanwhile there were no visible cracks in the center and end parts. Full width of half maximum of X-ray rocking curve on the plate crystal in center part of Ce:LYF bulk single crystal was 81.4 arcsec. Alpha-ray position in the pulse-height spectra under alpha-ray irradiation was almost quarter that of Li-glass(GS20). Decay times of the crystals in center and end parts were 69.9 and 58.3 ns, respectively (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Some Eu-doped scintillators, such as Eu:SrI2, emit around 400-nm wavelength that originates from 5d-4f transition of Eu2+, while some Eu-doped crystals have emissions from Eu3+ (f-f emission). In this report, effect of Eu-doping on optical and scintillation properties of SrF2 crystals with Core-valence luminescence is discussed. The samples had 0.1, 0.2, 0.5, 1.0, and 2.0 mol% of Eu and were grown by an annealing method. As a result, 5D0-7Fi (i =1, 2) transition (Eu3+) was detected in the SrF2, containing over 0.5 mol% of Eu, while emission from 0.1 and 0.2-mol% Eu:SrF2 originated from 5d-4f transition of Eu2+ and Core-valence luminescence. The light output of SrF2 doped with 0.1, 0.2, 0.5, 1.0 and 2.0 mol% Eu was estimated to be 13,000 ± 1,000, 12,000 ± 1,000, 13,000 ± 2,000, 8,000 ± 1,000 and 7,000 ± 1,000 photons/MeV, respectively. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

We have grown shape-controlled langasite-type crystals by the micro-pulling-down (μ-PD) method. Columnar shaped La3Ta0.5Ga5.5O14 (LTG), Ca3NbGa3Si2O14 (CNGS), Ca3TaGa3Si2O14 (CTGS), Sr3NbGa3Si2O14 (SNGS), and Sr3Ta- Ga3Si2O14 (STGS) crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die at the bottom. All grown crystals showed high transparency except for the peripheral area and diameter of approximately 3 mm. The chemical phases at the central parts of the grown crystals were identified as a single phase of langasite-type structure and their lattice parameters were almost the same as those of crystals grown by the Czochralski (Cz) method; however, some impurity phases were observed in the peripheral area. In X-ray rocking curve measurements, the grown crystals indicated equivalent crystallinity to the crystal grown by the Cz method. The piezoelectric constant d11 of the CNGS crystal was 3.98 pC/N; this value is well correlated with those of previous reports. [ABSTRACT FROM AUTHOR]

We grew column-shaped Sr3NbGa3Si2O14 (SNGS) and Sr3TaGa3Si2O14 (STGS) langasite-type piezoelectric single crystals by the micro-pulling-down (μ-PD) method. 3-mm-diameter SNGS and STGS crystals were grown using a Pt-Rh crucible with a 3-mm-diameter columnar die. According to X-ray rocking curve measurements, the grown crystals had crystallinity equivalent to that of crystals grown by the Czochralski (Cz) method. The crystals were single-phase materials with langasite-type crystal structure. The lattice parameters of the grown crystals were almost consistent with those of crystals grown by the Cz method. [ABSTRACT FROM AUTHOR]

Abstract: Columnar-shaped La3Ta0.5Ga5.5O14 single crystals with a-axis and c-axis crystal orientations along the growth direction grown by the micro-pulling-down method and their physical properties were investigated. All diffraction peaks of the XRD pattern were identified as the langasite-type structure and the a-axis and c-axis lengths were a=8.239Å and c=5.124Å, respectively. In the XRC measurement, a relatively sharp single peak was observed in the ω scan and the full width of half maximum was 82.1arcsec. According to the chemical analysis by the EPMA system, the main phase was composed of LTG with the cation ratio of La:Ta:Ga=3.31:0.465:5.22 and the LTG crystal included secondary phase, La–Ta–O system, in the periphery area. The piezoelectric constant d 11 that was measured using the plate-shape LTG crystal was 6.7pC/N. [Copyright &y& Elsevier]

Abstract: We have grown the Sc and Ce doped LiYF4 [Sc,Ce:LYF] single crystals with various Sc and Ce concentrations and investigated the effects of ionic radius control at Y site by Sc doping on crystal growth and physical properties. All grown Sc,Ce:LYF crystals included the milky and transparent parts and the amount of the milky parts in the crystals was smaller than that of the Ce:LYF crystal. The milky parts were composed of the LYF main phase and YF3 inclusion and in contrast, the transparent parts were a single phase of LYF. The lattice parameters were almost constant for all Sc,Ce:LYF crystals. Full width at half maximum of the XRC for Sc5%Ce5%:LYF crystal was 86.8arcsec and the effective segregation coefficients of Ce3+ ion in the Sc3%Ce3% and Sc5%Ce5%:LYF crystals were 0.21 and 0.18, respectively. In the transmittance and photoluminescence spectra, no clear effects of Sc co-doping were observed. [Copyright &y& Elsevier]

Abstract: The Ca3NbGa3Si2O14 (CNGS) crystal was grown by the micro-pulling down (μPD) method and the annealing effect on physical properties of CNGS crystal was investigated in this study. And the effects of oxygen content on the physical properties were systematically studied. Additionally, Photoluminescence (PL)-Mapping and radioluminescence spectra of CNGS were observed. The absorption peaks were observed around 350 and 500nm. This absorption at 500nm was very sensitive to a quantity of excess oxygen in the CNGS crystal. In contrast, it is expected that the absorption of 350nm is related to a cation or anion defect. PL-Mapping indicated the emission around 400nm by excitation at 270 and 350nm wavelengths. The emission at 400nm is considered to originate from trapped electron at an anion or cation defect. The emission of the Alpha-ray excited spectra was very similar in comparison with PL-Mapping. [Copyright &y& Elsevier]

Abstract: Nd, Ho, Er, and Tm doped lutetium aluminum garnet (LuAG) single crystals were grown using the micro-pulling down (μ-PD) method. The crystals were produced from the melts containing 3mol% of the dopants. The axial and radial dopant distribution were measured by electron probe micro analysis. Nd3+ and Ho3+ ions concentrated in the rim (k 0<1) and the radial concentration showed concave curvature. k 0 is the segregation coefficient of the dopant with respect to the given host phase. In the case of Er3+ and Tm3+ ions, the k 0 value is considered to be nearly 1 and the radial dopant distribution profiles were almost flat. [Copyright &y& Elsevier]

Abstract: We developed a modified micro-pulling-down (μ-PD) method for the crystal growth of halide materials with highly hygroscopic nature. A removable chamber system of the modified μ-PD method that can enter a globe box filled with Ar gas enabled to handle starting materials, set up a crucible and hot zone, grow a single crystal from the melt and take out a grown crystal without exposing to outside atmosphere. By the modified μ-PD method, CeCl3 and Ce 1% doped LaBr3 single crystals, which were famous as scintillator with high light yield and energy resolution were grown. Grown CeCl3 and Ce:LaBr3 single crystals indicated high transparency and they have no visible cracks and inclusions. In photoluminescence measurements, emission peak around 365nm was observed for CeCl3 single crystal and Ce:LaBr3 single crystal indicated two emission peaks around 360 and 380nm, which originated from 5d–4f transition of Ce3+ ion. [Copyright &y& Elsevier]

Abstract: We developed a growth technique of shape-controlled and multiple crystals by a micro-pulling-down (μ-PD) method using a developed special configuration crucible. A square tube-shaped sapphire crystal was grown with a molybdenum crucible with square tube die of 4mm×4mm outer periphery and 2mm×2mm inner periphery on the bottom. In contrast, six multiple square-shaped sapphire crystals were simultaneously grown by a molybdenum crucible with six circularly arranged square-shaped dies with a size of 2×2mm2 on the bottom. Growth of six multiple square-shaped sapphire crystals indicated a single phase of α-Al2O3 and almost same lattice parameters by X-ray diffraction measurement. Crystallinities of the six crystals were high in all positions of crystals comparable to the crystals grown by the Czochralski method. [Copyright &y& Elsevier]

Abstract: Effect of Ce content on the γ-ray response of LiYF4 single crystals with four different Ce concentrations is reported. The LiYF4 crystals were grown by the micro-pulling down method (μ-PD) with Ce content ranged from 0.1 to 10mol%. The emission spectra of all samples under α-ray (241Am) excitation are due to the Ce3+ 5d–4f transition and are characterized by a band at about 320nm. The pulse height spectra under γ-quanta (137Cs) were successfully observed and light yields were evaluated to be about 2800±280 (2mol%), 3000±300 (5mol%), and 3700±370 (10mol%)phs/MeV, respectively. The energy resolution decreased with increasing of Ce concentration as follows: 12±3 (2mol%), 19±3 (5mol%), and 30±22 (10mol%) %, respectively. The α/γ ratio were evaluated to be about 0.18 (2mol%), 0.175 (5mol%), and 0.15 (10mol%), respectively. The non-proportionality curve of specimen with Ce 5mol% doping exhibited good proportionality. Furthermore, the decay time examined with pulsed X-ray irradiation, detected using a streak camera, decreased with increasing of Ce concentration. [Copyright &y& Elsevier]