Pulling-down Method Research Articles

Stability or Instability of a Static Liquid Bridge Appearing in Shaped Crystal Growth from Melt via the Pulling-Down Method

Abstract: This study presents sufficient conditions for the stability or instability of the static liquid bridge appearing in crystal growth from the melt of micro-fibers, thin plates, and hollow micro-tubes of predetermined sizes using the pulling-down method [...]

Improving the CRI of Al2O3-YAG:Ce eutectic for high-power white LEDs applications: Energy-transfer and co-luminescence

Al2O3–Y3Al5O12:Ce (Al2O3-YAG:Ce) eutectic with weak attenuation at high temperature has a wide range of applications in high-power white light solid-state lighting. However, the general color rendering index (general CRI, Ra, the average value of R1-R8) of phosphor-converted white light-emitting diode (Pc-WLED) based on this material is usually no higher than 70 (CCT < 6500 K). We grew Al2O3-YAG eutectics doped with three ions of Ce3+, Pr3+, and Cr3+ by the micro pulling-down (μ-PD) method to improve the Ra through the co-luminescence and energy-transfer. The co-luminescence and energy-transfer were analyzed by the excitation-emission spectrum and the spectral power distribution. Results show that the energy-transfer between Ce3+ and Pr3+ ions in Al2O3-YAG:Ce, Pr occurs with each other, visibly enhancing the emission at around 610 nm and 694 nm, increases the Ra by 8.4 compared to Al2O3-YAG:Ce. Moreover, the Ra of the Al2O3-YAG:Ce and Al2O3-YAG:Cr stacked Pc-WLED increases by 20.4 compared to Al2O3-YAG:Ce, reaching 78.7. In addition, (R9, the special CRI for strong red, is 59.). In addition, the annealed (H2) single-doped eutectics have little change compared to unannealed ones in luminescence, but the co-doped ones with multiple ions have a significant change. Significantly, the luminous efficiency of Al2O3-YAG:Ce after annealing is only increased by 4%, while that of Al2O3-YAG:Ce, Pr is increased by 13%. These studies show that the CRI of Pc-WLED base on Al2O3-YAG:Ce eutectic can be improved by ion co-doping in eutectic or superposition of Al2O3-YAG eutectic doped with other ions.

Magnetic properties of manganese doped PrAlO3 monocrystalline fibres

Abstract Monocrystalline fibres of undoped PrAlO3 and PrAlO3:0.1 Mn, have been grown by the pulling-down method under nitrogen atmosphere. The as-grown crystal doped with Mn had a visible brown core surrounded by a green ring, whereas this effect was weaker for the undoped PrAlO3. A coloration of the brown core was caused by a presence of Pr4+ ions. The presence of the Pr4+ ions was confirmed by XPS and magnetic studies. The XPS chemical analysis showed the increased concentration of oxygen in the crystals with the brown core. The most probable valency of manganese is Mn4+. It is located in Al3+ sites.

Crack Behavior of Si-Doped GaAs Crystals Grown by Pulling-Down Method

The crack behavior of Si-doped GaAs crystals produced by a novel pulling-down method was investigated. Some cracks were observed in the crystal tail part and no twins or polycrystals were observed. The cracking mechanism was discussed considering the growth parameters, such as the pulling-down rate, annealing time and cooling speed of the furnace. The crystal was easily broken if the cooling rate was too fast. To avoid cracking, the temperature profile and the growth parameters had been optimized. The cleavage property of the GaAs crystal was strongly related to its atomic arrangement and corresponding electron density map. Ultrasonic vibration or mechanical machine would make the crystal cleaved along (110) plane. GaAs crystal displayed a strong anisotropic crack property under the force of microindentation test.

Existence and Stability of the Solution of a Nonlinear Boundary Value Problem

The purpose is to find conditions assuring the existence of solutions for a nonlinear, boundary value problem in case of the axis‐symmetric Young‐Laplace differential equation. The equation describes the capillary surface between two static fluids. Necessary or sufficient conditions are found for the existence of a solution. The static stability of the obtained solution is also analyzed and stability or instability results are revealed. For the NdYAG microfiber growth, by the pulling‐down method, numerical illustrations are given.

Defects of GaAs Crystals Grown by the Pulling-Down Method

Compound semiconductor GaAs crystal was grown by the pulling-down method and the Φ2" GaAs boules were obtained. The growth defects, such as growth stripes, small facets, pits and dislocations, were observed. The pits on the surface of the boule was attributed to the water content of B2O3 encapsulant and the growth defects on the tail were associated with the evaporation of As due to GaAs decomposition. The average EPD (etch pit density) was measured less than 5000 cm-2, which shows the pulling-down method was a potential technique to grow high quality GaAs crystals.

Growth of Undoped GaAs Single Crystal by Pulling-Down Method

Undoped GaAs single crystal has been grown in PBN crucibles by the pulling-down method. The temperature profile of the furnace was optimized with a narrow melting zone and a small temperature gradient at the solid-liquid interface. Quartz ampoules were used to protect the evaporation of As during the growth and the deformation of the ampoule was discussed as a function of temperature, time and pressure differential. A Ø56 mm×70 mm GaAs crystal with nearly 100 % single crystalline yield was obtained. X-ray rocking curve analysis revealed the excellent crystalline quality. The average EPD and electrical properties of the crystal were tested comparable to those of the crystal produced by the VGF method. Therefore, the pulling down method was a feasible approach for GaAs crystal production.

Elastic and Superelastic Properties of NiFeCoGa Fibers Grown by Micro-Pulling-Down Method

Low-frequency elastic modulus, internal friction, tensile stress-strain loops, and thermally-induced strain recovery of single-crystal fibers obtained by pulling-down method from the melts of NiFeGaCo alloys were studied. A minimum of the elastic modulus and the maximum peak of the internal friction were obtained at the martensitic transition temperature. A large super-elastic strain of about 10% was obtained in the fiber of the Ni49Fe18Ga27Co6 alloy. Thermodynamic estimation by the Clausius-Clapeyron equation was consistent with the experimental results.

Evaluation of Fiber-Shaped LYSO for Double Readout Gamma Photon Detection

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> Recently, the development of the micro pulling-down method has allowed the growth of single inorganic scintillation crystals with a uniform fiber shape. The dimensions may vary from 0.3 to 3 millimeters in diameter with length up to 1 meter. </para>

{Y 3− x,Yb x}[Ga] 2(Ga) 3O 12 and {Lu 2Yb 1}[Al] 2(Al) 3O 12 single crystals for scintillator application grown by the modified micro-pulling-down method

In order to investigate proper hosts for charge transitions (CT) of Yb 3+, the gallium garnet host (YGG) and aluminium garnet host (LuAG) were studied. Transparent and crack-free heavily Yb-doped YGG, i.e. {Y 3− x ,Yb x }[Ga] 2(Ga) 3O 12, x=0.15, 0.5, 1.0 and heavily Yb-doped LuAG, i.e. {Lu 2Yb 1}[Al] 2(Al) 3O 12 single crystals were grown by the modified pulling-down method with 〈1 1 1〉 orientation. Emission, excitation spectra and decay kinetics were measured for these crystals. The CT of Yb 3+ in the YGG host were discussed compared with the Yb 3+ one in the LuAG host.

Facet formation during fiber pulling from the melt

Dimensional stability of a fiber growing by the micro pulling-down method is analyzed taking into account specific crucible geometry and the shape of the molten meniscus. This analysis reveals some features peculiar for the pulling of faceted fibers. On the boundary of a faceted fiber the usual assumption of a steady state interfacial growth angle φ 0 is not correct. It has to be replaced with the condition of a fixed meniscus (anchoring) on a sharp facet edge. This makes the range of permissible meniscus shapes considerably wider. Corresponding solutions of the Young–Laplace equation and a semi-quantitative capillary model to explain the periodicity in the formation of faceted ridges is given.

Growth of oxide single crystals by the pulling-down method with a continuous feeding system

Growth of oxide single crystals by the pulling-down method with a continuous feeding system

Growth of Bi12GeO20 Single Crystals by the Pulling-Down Method with a Continuous Powder Feed System.

Transparent and crack-free Bi12GeO20 single crystals have been grown by the pulling-down method with a continuous powder feed system. Bi-rich feed powder having a composition of 14.1mol% GeO2 is favorable to obtain stoichiometric crystals. Striation-free crystals with an increased transmittance are grown under a small temperature gradient. The shape of the solid-liquid interface during the crystal growth is nearly flat, which is advantageous to avoid core formation. Average dislocation density is estimated to be 2×104/cm2, which is comparable to that of Bi12GeO20 crystals grown by the conventional Czochralski method.

Growth of Bi 12SiO 20 single crystals by the pulling-down method with continuous feeding

Bi 12SiO 20 single crystals were successfully grown by the pulling-down method with continuous feeding. As-grown crystals were amber in color and transparent, and had no cracks or inclusions. A crystal with homogeneous composition was obtained from Bi-rich feed powder having a composition of 14.1 mol% SiO 2, whereas precipitates of Bi 4Si 3O 12 were observed on the surface of a crystal grown with stoichiometric powder. The shape of the solid–liquid interface during the crystal growth was estimated to be almost flat, which was favorable to avoid core formation. Average dislocation density was 4×10 3/cm 2, which was comparable to that of Bi 12SiO 20 crystals grown by the Czochralski method.

Optical Properties of Er3+ Ions in Calcium Niobium Gallium Garnet (CNGG) Crystals

Single crystals of Er3+-doped calcium niobium gallium garnet (CNGG) were grown using the Czochralski technique, and the single crystal fibers with diameter of 0.81 mm were grown by the micro pulling-down method. The absorption and luminescence spectra by Er3+ ions in these materials have been investigated together with the luminescence decay. The same results are obtained between the crystals and fibers. Broad absorption lines are obtained which are suggested to be due to the Er3+ ions with various site symmetries. By the excitation with 266 nm radiation, the luminescence bands are observed at 490, 535, 545, 554, 656 and 669 nm. The 545 nm luminescence due to the 4S3/2 → 4I15/2 transition is found to have two decay components: the fast decay component of 15.1 μs and the slow component of 30.5 μs. A delay time of 3.7 μs was found between the excitation pulse and the 656 and 669 nm luminescence bands due to the 4F9/2 → 4I15/2 transition while no delay was found for the other luminescence bands.

Growth of rutile single crystals by the pulling-down method

Rutile single crystals were grown by the pulling-down method with continuous feeding. An iridium crucible having a hole at the bottom center was used and heated up by an rf-coil; it acted as a melt-supporting plate to grow large-diameter crystals. Because of poor wettability of the melt of rutile to the iridium crucible, the diameter of the hole at the crucible bottom should be 2 mm to realize continuous supply of the melt to the growth region. The use of a radiation-shielding plate made of porous zirconia improved the temperature gradient below the crucible, contributing smooth seed touch and stable molten zone during the growth run, and rutile single crystals up to 25 mm in diameter were consequently obtained. Long crystals of about 60 mm with a constant diameter were obtained using TiO 2 grains as feeding materials.

Flux Growth of KNbO3 Crystals by Pulling-Down Method

The crystals of KNbO 3 have been grown by the micro-pulling-down method. Colorless, transparent, and crack-free crystals were produced from the melts containing excess of K 2 O as a flux. Growth of relatively large size (up to 2 mm in diameter and up to 30 mm in length) single crystals was found is possible using the crucibles with corresponding nozzle size (up to 2.0 mm in outer diameter). Second harmonic generation was observed in the crystals irradiated by fundamental beam with wavelength about 860 nm.

23pA6 Growth of metal oxide single crystals by pulling-down method

23pA6 Growth of metal oxide single crystals by pulling-down method

Growth of rutile single crystals by the pulling-down method with continuous feeding

Growth of rutile single crystals by the pulling-down method with continuous feeding

Growth of Li_2B_4O_7 single crystals by the pulling-down method with continuous feeding

Growth of Li_2B_4O_7 single crystals by the pulling-down method with continuous feeding