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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]

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]

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]

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]

• 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: 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: 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]

• 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]

A new method for evaluation of homogeneity of Ca 3 Ta(Ga 0.5 Al 0.5 ) 3 Si 2 O 14 (CTGAS) single crystals was established based on leaky surface acoustic wave (LSAW) velocity measurements performed by the line-focus-beam ultrasonic material characterization (LFB-UMC) system. Three plate specimens cut perpendicular to X -, Y -, and Z -axes were prepared from the CTGAS crystal ingot and LSAW velocity distributions were examined for these specimens. LSAW velocity changes due to Al-substitution effect were successfully extracted by using a relationship between two LSAW velocities propagating along different directions for Ca 3 TaGa 3 Si 2 O 14 (CTGS) and Al-substituted CTGS. Comparison of measured LSAW velocities and the results of chemical composition analysis performed by electron probe microanalysis (EPMA) demonstrated that LSAW velocity is mainly affected by Al-content change in CTGAS. Maximum velocity variation was observed in radial direction of the crystal ingot through the Z -axis propagating LSAW velocity measurements for Y -cut CTGAS specimen corresponding to Al-content change of 0.226 mol%. Accuracy of evaluation of Al content by velocity measurement for Y -cut Z -propagating LSAW is estimated to be ±0.0047 mol% and is superior to that by EPMA. [ABSTRACT FROM AUTHOR]

Abstract: Ce:Gd3(Al x Ga1−x )5O12 (x=2.5/5 and 3/5, Ce:GAGG-2.5 and Ce:GAGG-3) crystals were grown by the Czochralski process in order to reduce cost of the starting materials as compared with conventional Ce:Gd3Al2Ga3O12 (Ce:GAGG-2) crystal which have high light output. Although perovskite phase was detected in Ce:GAGG-3, Ce:GAGG-2.5 had single-phase garnet structure. Solidification fraction for the Ce:GAGG-2.5 growth was 0.52. Optical properties including transmittance, emission, and excitation spectra of 30 samples cut from the Ce:GAGG-2.5 bulk ingot did not depend on their original position along the growth axis. These samples had light outputs of approximately 58,000±3000 photons/MeV. However, scintillation decay times varied from 140 to 200ns and depended on the position clearly. [Copyright &y& Elsevier]

Ce0.5%: Ce:Gd 3 Ga 3 Al 2 O 12 (GGAG) single crystals co-doped with 500at.ppm Li + , Na + and K + were grown by using the micro-pulling down method. The smooth Ce 4+ charge transfer absorption below 350 nm and decay time acceleration were observed in Li co-doped sample. Na + and K + co-doping did not show a large effect on the acceleration of decay time compared with Li co-doping. Ce0.5%:GGAG single crystals co-doped with 500 at.ppm Li + were also grown by the Czochralski method. Optical, scintillation properties and timing performance were evaluated to investigate the effect of univalent alkali metal ions co-doping on Ce:GGAG scintillators. The scintillation decay curves were accelerated by Li co-doping: the decay time was significantly accelerated to 54.8 ns (47%) for the faster component and 158 ns (53%) for the slower component. The light output was 94% of the non co-doped Ce:GGAG standard. The coincidence time resolution was improved to 258 ps by Li co-doping. [ABSTRACT FROM AUTHOR]

Ce-doped (Gd, La) 2 Si 2 O 7 scintillation crystals are expected to be used as gamma-ray detectors for high temperature measurement. To realize scintillators for high temperature environment, we investigated (Ce 0.01 Gd 0.59−x La 0.40 Y x ) 2 Si 2 O 7 (x = 0.00, 0.05, 0.10, 0.15) single crystals grown by the micro-pulling-down method. The results showed that a 5% Y-admixed Ce-doped (Gd, La) 2 Si 2 O 7 scintillator can yield higher light output when compared with Y-free Ce-doped (Gd, La) 2 Si 2 O 7 scintillator. The light outputs at 25°C and 175°C were determined to be ∼43,000 and ∼40,000 photons/MeV, respectively. Moreover, 1 inch size 5% Y-admixed Ce-doped (Gd, La) 2 Si 2 O 7 scintillator was grown by the Czochralski technique, and its light output at 175°C kept the value of around 95% of the value at 25°C. [ABSTRACT FROM AUTHOR]

Mg co-doped Ce1%:Gd 3 Ga x Al 5−x O 12 (Ce:GAGG) crystals (x=2.4, 2.7, 3.0) were successfully grown by the Czochralski (Cz) method. Effect of Mg co-doping on the scintillation properties of Ce:GAGG was examined. This study covers measurements of solidification fraction and scintillation properties such as light yield, energy resolution and non-proportionality for each crystal. Pulse-height spectra of various gamma and X-ray sources with energies ranged from 30 keV to 662 keV were measured. Regardless of the presence/absence of Mg dopant, the non-proportionality curves with lower content of gallium in the crystal structure tend to improve. Mg co-doped Ce:GAGG samples did not show a significant difference as compared with non co-doped Ce:GAGG. Mg co-doped crystals with x=2.4 and 2.7 showed the promising scintillation properties of faster decay time and higher energy resolution than those with x=3.0. [ABSTRACT FROM AUTHOR]

Ce-doped Lu 2 Si 2 O 7 scintillator contains radioactive isotope 176 Lu which causes an unwanted intrinsic background signal. The development of scintillators with reduced Lu concentration were required in some applications. In this study, we developed the Gd admixed lutetium pyrosilicate, where the average ion radius at the rare earth site was similar to the Tm 3+ ion radius, for which the RE 2 Si 2 O 7 (RE=Tm, Yb, Lu) crystal structure is stable from room temperature to melting point. We have grown (Ce x Lu 1−x−y Gd y ) 2 Si 2 O 7 (x=0.01, y=0.00, 0.05, 0.10) single crystals. Their crystal systems were monoclinic with a space group C 2/ m . The absorption spectra revealed the energy transitions in Ce and Gd ions might be occurred. The light output was degraded and decay time was accelerated comparing the Gd 5% admixed sample with the Gd 10% one. [ABSTRACT FROM AUTHOR]

The relationship among lattice constant a , Al content, and acoustic properties were experimentally examined using a plate specimen perpendicular to Y -axis prepared from Ca 3 Ta(Ga 0.75 Al 0.25 ) 3 Si 2 O 14 [CTGAS(0.25)] single crystal grown by Czochralski method. As the acoustic properties, leaky surface acoustic wave (LSAW) velocities with different propagation directions, X - and Z -propagations, and longitudinal wave velocity propagating along Y -axis direction were measured by the line-focus-beam/plane-wave ultrasonic-material-characterization (LFB/PW-UMC) system. The measured results of LSAW velocity distributions revealed inhomogeneity in radial direction of the crystal ingot exhibiting lower velocity area at the center of the ingot. In addition, the distributions of lattice constant a and chemical composition (especially Al content) were measured along the radial direction. Abnormal changes suggesting existence of residual stresses concentrated on the central part of the crystal ingot other than the effect of chemical composition change were detected from the relationships among the measured parameters. [ABSTRACT FROM AUTHOR]

The 3 in. size Ce1%:Gd 3 Al 2 Ga 3 O 12 single crystals were prepared by the Czochralski (Cz) method. Optical constants were measured. Chemical composition analysis and uniformity of scintillation decay and light yield along growth direction were evaluated. The timing resolution measurement for a pair of 3 mm×3 mm×3 mm size Ce:GAGG scintillator crystals was performed using Si-PMs. [ABSTRACT FROM AUTHOR]

The Li + co-doped Ce:Lu 3 Al 5 O 12 single crystals were prepared by micro pulling down method. Absorption and luminescence spectra were measured together with several other scintillation characteristics, namely the scintillation decay and light yield to reveal the effect of the co-doping. The smooth Ce 4+ CT absorption below 350 nm is clearly enhanced with increasing concentration of Li. The scintillation decays were accelerated and light yields were increased by Li co-doping. [ABSTRACT FROM AUTHOR]

To improve the dopant homogeneity in the radial direction, the micro-pulling-down apparatus was modified for Ce-doped Y 3 Al 5 O 12 (Ce 3+ :YAG) crystal growth. Two effective crucible variants, diffusion-channel and multi-channel crucibles, were adopted to alleviate the inhomogeneity of dopant concentration in the radial direction. In the diffusion-channel model, two different inclination angles were investigated. The results demonstrate that the radial dopant distribution at the melt-crystal interface (i.e., the growth front) is improved notably by using the diffusion-channel crucible. Furthermore, the better radial distribution is achieved with the larger inclination angle. In the multi-channel model, more capillary–channels result in a smaller inflow velocity from every single capillary-channel with the same growth rate. Therefore, the effect of inflow on the dopant distribution is reduced, and thus the radial dopant homogeneity is improved apparently. Besides, although the symmetry of concentration distribution along the azimuthal direction is broken in the multi-channel model, the whole homogeneity of dopant at the melt-crystal interface is ameliorated. [ABSTRACT FROM AUTHOR]

Abstract: The Nd-doped Lu3Al5O12 (Nd:LuAG) single crystal was grown by the Czochralski (CZ) method. In XRC profiles, the full-width at half-maximum (FWHM) value was 58arcsec, which was much higher than that of the μ-PD (194arcsec). In photo and radio-luminescence spectra, the CZ grown sample showed strong emission peaks attributed to Nd3+ 4f–4f transitions in visible wavelengths longer than 400nm. The Nd:LuAG grown with the CZ method showed light yield of 7900 photons/MeV, which is comparable with the standard BGO and energy resolution of 14% under 137Cs γ-ray excitation. [Copyright &y& Elsevier]

Abstract: The growth of Y2O3, Sc2O3, and Lu2O3 single crystals using the micro-pulling-down method is reported. Crystallinity, optical transmittance, and scintillation characteristics including emission spectra, pulse height spectra, and decay kinetics under α-ray excitation of the grown crystals were studied. The light yields of Y2O3, Sc2O3, and Lu2O3 crystals were estimated from the pulse height spectra excited by 241Am 5.5MeV α-rays, in about 920±92ph/5.5MeVα, 370±37ph/5.5MeVα, and 150±15ph/5.5MeVα, respectively. The scintillation decay times of Y2O3, Sc2O3, and Lu2O3 crystals were estimated with following fast/slow parameters 30.1/184, 14.6/51.3, and 16.7ns, respectively. Furthermore, α-ray imaging was performed using Y2O3 crystal. [Copyright &y& Elsevier]

• (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]

• W co-doped Ce:Gd 3 Ga 3 Al 2 O 12 with 30–60 mm length grown by micro-pulling down method. • Light yield value was increased by small amount (200–1000 ppm) of W co-doping. • When the co-doping concentration of W was higher than 1000 ppm, the light yield decreased. Single crystal scintillators are extensively used in various radiation detection applications and their scintillation performances can be improved via co-doping. Therefore, in this study, tungsten-ion co-doped Ce:Gd 3 (Ga,Al) 5 O 12 (Ce:GGAG) crystals were grown using the micro-pulling-down (μ-PD) method to investigate the effects of co-doping on their scintillation properties. The relationships between the W concentration, optical and luminescence properties, and radiation response of the W-co-doped Ce:GGAG crystals were evaluated. The W-co-doped Ce 0.5%:Gd 3 Ga 3 Al 2 O 12 single crystals of diameter 3 mm and length 30–60 mm were grown by the μ-PD method. The light yield increased at W concentrations of 200 and 500 ppm and decreased at W concentrations above 1000 ppm. There was no significant change in the fast decay component of scintillation. [ABSTRACT FROM AUTHOR]

• Feasibility of the growth of LYSO, YSO, LuAG, YAG and GAGG by EFG was studied. • Aluminate such LuAG and YAG had the least reactivity with Mo metal. • Ce:LuAG with 320 mm length were grown by 4 multiple EFG using Mo crucible and die. • Light yield value was high and nearly constant within 25,000–27,200 photon/MeV. Edge defined Film Fed Growth (EFG) method with molybdenum (Mo) crucible and die was studied for the growth of several oxide-based single crystals. At first, reactivity between the molybdenum (Mo) metal and oxide melts of Ce:(Lu,Y) 2 SiO 5 (LYSO) Ce:Y 2 SiO 5 (YSO), Ce:Gd 3 (Al,Ga) 5 O 12 (GAGG), Ce:Lu 3 Al 5 O 12 (LuAG), Ce:Y 3 Al 5 O 12 (YAG) was investigated. The experimental and calculation results on the reactivity with Mo show that the aluminum garnets (LuAG, YAG) had the smallest reactivity with Mo metal. On the contrary, GAGG showed the strongest reaction with Mo. Then, the multiple-die grown shaped single crystal growth of Ce:LuAG was demonstrated by EFG method. Single crystal plates up to 320 mm in length were grown successfully. The homogeneity of dopant distribution, Mo contamination, luminescence and scintillation responses of the grown crystals were evaluated. [ABSTRACT FROM AUTHOR]