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We have developed a laser-diode-heated floating zone (LDFZ) method, in order to improve the broad and inhomogeneous light focusing in the conventional lamp-heated floating zone method, which often causes difficulties in the crysta...
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We have developed a laser-diode-heated floating zone (LDFZ) method, in order to improve the broad and inhomogeneous light focusing in the conventional lamp-heated floating zone method, which often causes difficulties in the crystal growth especially for the incongruently melting materials. We have simulated the light focusing properties of the LDFZ method to make the whole of the molten zone irradiated with concentrated and homogeneous laser lights. We have designed and assembled an LDFZ furnace, and have demonstrated how it works through actual crystal growth. The method is applicable to various kinds of materials, and enables stable and reproducible crystal growth even for the incongruently melting materials. We have succeeded in the crystal growth of representatives of the incongruently melting materials such as BiFeO_3 and (La,Ba)_2CuO_4, which were believed to be difficult to be grown by the conventional method. Tolerance to the decentering of samples and highly efficient heating are also established in the LDFZ method.
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We performed a crystal growth to obtain chirality-controlled enantiopure crystals using a laser-diode-heated floating zone (LDFZ) method with a composition-gradient feed rod. It has been argued that the crystal handedness of TSi (...
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We performed a crystal growth to obtain chirality-controlled enantiopure crystals using a laser-diode-heated floating zone (LDFZ) method with a composition-gradient feed rod. It has been argued that the crystal handedness of TSi (T : transition metal) is fixed depending on T in the case of the ones grown by the conventional methods. We found that right-handed single crystals of CoSi and MnSi were grown from the composition-gradient feed rods that consist of FeSi-CoSi and FeSi-MnSi, respectively. The obtained CoSi and MnSi crystals inherit the chirality from the seed part of FeSi, which grows in a right-handed structure, and thus has the chirality opposite to that for the crystals in the literature. The LDFZ method with the feed rods with various combinations of TSi compounds enables flexible control of the chirality of TSi and will be useful for clarifying the interplay between crystalline chirality and chirality-induced physical responses.
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This paper presents the results of photoluminescence and X-ray induced scintillation properties of xCe:33.3BaO-66.6SiO(2) (x = 0, 0.05, 0.1, 0.5, 1.0, 2.0) glasses produced by the Floating Zone (FZ) method. We observed intense emi...
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This paper presents the results of photoluminescence and X-ray induced scintillation properties of xCe:33.3BaO-66.6SiO(2) (x = 0, 0.05, 0.1, 0.5, 1.0, 2.0) glasses produced by the Floating Zone (FZ) method. We observed intense emission from 5d-4f transition of Ce3+ and the concentration quenching with the increase of Ce concentration in photoluminescence (PL) and scintillation properties. The lowest Ce-doped sample indicated the highest scintillation intensity in the X-ray induced scintillation measurement. The non-doped sample had the highest afterglow level, and the afterglow levels decreased with Ce addition amount. From these results, it was found to be in a trade-off relationship between the scintillation intensity the and afterglow characteristics in present samples.
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The crystal growth, polarized spectral properties, Judd-Ofelt (JO) analysis and lifetime of Sm:CaGdAlO4 (Sm:CGA) crystal were reported for the first time. Sm:CGA crystal with size of 44 x 33 mm(3) was grown by the floating zone (F...
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The crystal growth, polarized spectral properties, Judd-Ofelt (JO) analysis and lifetime of Sm:CaGdAlO4 (Sm:CGA) crystal were reported for the first time. Sm:CGA crystal with size of 44 x 33 mm(3) was grown by the floating zone (FZ) method. The peak absorption cross-sections at 407 nm were calculated to be 3.41 x 10(-20)cm(2) and 3.20 x 10(-20)cm(2) for the a and x polarization, and the largest stimulated emission cross-sections at 601 nm were 5.10 x 10(-21)cm(2) and 4.66 x 10(-21)cm(2), respectively. The absorption and emission cross-sections were several times larger than that of Sm:LiYF4. The JO intensity parameters of Omega(2), Omega(4) and Omega(6) were calculated to be 3.0 x 10(-20)cm(2), 6.1 x 10-20cm(2) and 6.5 x 10(-20)cm(2), respectively. The lifetime of the (4)G(5/2) level was obtained to be 0.69 ms. All the results indicate that Sm:CGA crystal is a potential laser host for the reddish-orange laser operation. (C) 2017 Elsevier B.V. All rights reserved.
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Effect of silica additive on the formation of lotus-type porous alumina on the unidirectional solidification was examined. Lotus-type porous alumina with 44 percent porosity was formed by unidirectional solidification using the op...
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Effect of silica additive on the formation of lotus-type porous alumina on the unidirectional solidification was examined. Lotus-type porous alumina with 44 percent porosity was formed by unidirectional solidification using the optical floating zone method under a hydrogen atmosphere when low purity alumina was used as the feed rod. However, non-porous alumina v, as prepared in argon atmosphere. The formed pores possessed a drop-like shape and were elongated along the solidification direction in porous alumina. Gas bubbles evolved in the molten zone and was trapped by the solid/liquid interface during the unidirectional solidification. On the other hand, lotus-type porous alumina could not be obtained when high purity alumina was used as the feed rod. The porosity of the solidified porous alumina increased with increasing silica contents in the feed rods.
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Cerium-doped terbium gallium garnet single crystal having a large Verdet constant was grown by floating zone (FZ) method, which was suitable for the use in optical devices. The lattice parameters and the X-ray rocking curve measur...
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Cerium-doped terbium gallium garnet single crystal having a large Verdet constant was grown by floating zone (FZ) method, which was suitable for the use in optical devices. The lattice parameters and the X-ray rocking curve measurement of the crystal was determined by X-ray diffraction analysis. The Verdet constant of the crystal (B = 0.55 T) at the wavelength of 632.8 nm was -165.8 rad m(-1) T-1 at room temperature, 23.7% larger than that of pure TGG (-134.0 rad m(-1) T-1). The performance of the high optical quality and excellent magneto-optical properties of the crystal shows the great potential of using this new method to meet the increasing demand of VI-NIR Faraday rotators.
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Single crystals of CrB_2 up to 2.4 cm in diameter were prepared by the floating-zone method with radio-frequency induction heating. The electromagnetic coupling between the work coil and the sample, i.e. the heating efficiency, wa...
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Single crystals of CrB_2 up to 2.4 cm in diameter were prepared by the floating-zone method with radio-frequency induction heating. The electromagnetic coupling between the work coil and the sample, i.e. the heating efficiency, was improved by 40 percent by preparing the thick crystal rod at a higher feed rate of the feed sintered rod. Under these improved growth conditions, the heating power was proportional to the crystal diameter. The CrB_2 crystal was used as a substrate for epitaxial growth of gallium nitride and aluminum nitride.
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The stability of the axisymmetric thermocapillary convection flow in a floating zone model is studied with high precision tools. The 2-D perturbation breaks the symmetry of the steady flow around the mid-plane linked to the chosen...
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The stability of the axisymmetric thermocapillary convection flow in a floating zone model is studied with high precision tools. The 2-D perturbation breaks the symmetry of the steady flow around the mid-plane linked to the chosen parabolic lateral heat flux. This is observed for all considered Prandtl number values, namely, Pr ∈ [10~(-3), 10~(-1)] ∪ [9, 10~2]. A Hopf bifurcation is observed, giving rise to oscillatory flows, except for Pr ∈ [3.4 x 10~(-3), 3.15 x 10~(-2)] where a stationary transition occurs. To determine the mechanisms responsible for the growth of the perturbation requires various approaches.
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Single crystals of Ho2O3-doped Y2O3 stabilized ZrO2 (YSZ) with different Y2O3 and Ho2O3 contents were grown by the optical floating zone method. XRD and Raman spectra were measured and showed that crystal samples all had tetragona...
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Single crystals of Ho2O3-doped Y2O3 stabilized ZrO2 (YSZ) with different Y2O3 and Ho2O3 contents were grown by the optical floating zone method. XRD and Raman spectra were measured and showed that crystal samples all had tetragonal structures. Measurements of positron annihilation lifetime spectra indicated that the increase in Y2O3 concentration led to the increases of defects and mean positron lifetime, which enhanced the scattering of light and reduced the luminous intensity and the quantum yield (QY) of the crystal. Under the excitation at 446 nm, photoluminescence (PL) spectra of Ho2O3 -doped YSZ crystals showed emission peaks at 540, 551, 670, and 757 nm corresponding to Ho3+ transitions from 5S2, 5F4, 5F5, and 5I4 excited states to the 5I8 ground state, respectively. At low Ho2O3-doped concentrations (0.10–0.50 mol%), the overall emission intensity increased with Ho2O3 contents, reached the maximum value at 0.50 mol%, then decreased with higher Ho2O3 contents, probably as a result of increased non-radiative relaxation caused by increased interactions between Ho3+ ions. Quenching of the PL occurred at Ho2O3 concentrations > 0.5 mol% and due to the electric dipole–dipole interaction. The calculated chromaticity coordinates (CIE) were approximately (0.307, 0.683) and the color purity achieved 99.6%. The results showed that Ho2O3 YSZ crystals were suitable for green light-emitting devices.
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To make headway on any problem in physics, high-quality single crystals are required. In this talk, special emphasis will be placed on the crystal growth of various oxides (superconductors and magnetic materials), borides and carb...
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To make headway on any problem in physics, high-quality single crystals are required. In this talk, special emphasis will be placed on the crystal growth of various oxides (superconductors and magnetic materials), borides and carbides using the image furnaces at Warwick. The floating zone method of crystal growth used in these furnaces produces crystals of superior quality, circumventing many of the problems associated with, for example, flux growth from the melt. This method enables the growth of large volumes of crystal, a prerequisite especially for experiments using neutron beams. Some examples of experimental results from crystals grown at Warwick, selected from numerous in-house studies and our collaborative research projects with other UK and international groups will be discussed.
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