• Journal of the Korean Ceramic Society
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• v.56 no.6
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• pp.589-595
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• 2019

The top-seeded solution growth (TSSG) method is an effective approach for the growth of high-quality SiC single crystals. In this method, the temperature gradient in the melt is the key factor determining the crystal growth rate and crystal quality. In this study, the effects of the aperture at the top of the hot-zone on the growth of the SiC single crystal obtained using the TSSG method were evaluated using multiphysics simulations. The temperature distribution and C concentration profile in the Si melt were taken into consideration. The simulation results showed that the adjustment of the aperture at the top of the hot-zone and the temperature gradient in the melt could be finely controlled. The surface morphology, crystal quality, and polytype stability of the grown SiC crystals were investigated using optical microscopy, high-resolution X-ray diffraction, and micro-Raman spectroscopy, respectively. The simulation and experimental results suggested that a small temperature gradient at the crystal-melt interface is suitable for growing high-quality SiC single crystals via the TSSG method.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.1
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• pp.8-13
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• 2016

A top-seeded solution growth (TSSG) is a method of growing SiC single crystal from the Si melt dissolved the carbon. In this study, multiphysics modeling was conducted using COMSOL Multiphysics, a commercialized finite element analysis package, to get analytic results about electromagnetic analysis, heat transfer and fluid flow in the Si melt. Experimental results showed good agreements with simulation data, which supports the validity of the simulation model. Based on the understanding about solution growth of SiC and our set-up, crystal growth was conducted on off-axis 4H-SiC seed crystal in the temperature range of $1600{\sim}1800^{\circ}C$. The grown layer showed good crystal quality confirmed with optical microscopy and high resolution X-ray diffraction, which also demonstrates the effectiveness of the multiphysics model to find a process condition of solution growth of SiC single crystal.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1999.06a
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• pp.227-250
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• 1999

The reproducibility of successive growth of Bi12TiO20(BTO) single crystals using a top-seeded solution growth (TSSG) pulling method was evaluated by measuring the lattice constants and their standard deviations. A substantial phase diagram in the region close to the stoichiometric BTO was established experimentally for this purpose, and the existence of a retrograde solid solution close to a BTO was clarified. It was emphasize that a starting solution, with a 10.0~10.1 mol% TiO2 concentration, results in large single crystals with a highly homogeneous lattice constant of within $\pm$1x10-4$\AA$, when the solidified fraction of the grown crystal is less than about 45%. A wavelength dispersion of refractive index was measured for the first time, an it was verified that the refractive index of BTO is larger than that of BSO(Bi12TiO20), allowing the voltage sensitivity of EOS higher than the case with BSO as a probe head.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.4
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• pp.424-431
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• 1999

The reproducibility of successive growth of $Bi_{12}TiO_{20}$ (BTO) single crystlas using a top-seeded solution growth (TSSG) pulling method was evalutated by measuring the lattice constants and their standard deviations. A substantial phase diagram in the region close to the stoichiometric BTO was established expermentally for this purpose, and the existence of a retrograde solid solution close to a BTO was clarified. It was emphasized that a starting solution, with a 10.0~10.1 mol% $TiO_{2}$ concentration, results in large single crystals with a highly homogeneous lattice constant of within ${\pm}1{\times}10^{-4}\AA$, when the solidified fraction of the grown crystal is less than about 45 %. A wavelength dispersion of refractive index was measrued for the first time, and it was verified that the refractive index of BTO is larger than that of BSO($Bi_{12}TiO_{20}$), allowing the voltage sensitivity of EOS higher than the case with BSO as a probe head.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1997.06a
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• pp.149-155
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• 1997

We have successfully grown colorless and transparent Rb-doped potassium niobate (KRN) single crystals using the top seeded solution growth(TSSG) technique. In our crystal growth experiments, the Rb doping concentrations within the melt range from 2-15 mol% relative to that of Nb$_2$O5. Atomic absorption measurements indicate that the Rb content in the KRN solid solution is rather low; the Rb segregation coefficient is found to be on the order of 0.05. It is believed that this is due to the relatively much larger Rb+ ionic radius compared to that of K+, rendering it more difficult for Rb to replace K in the KNbO$_3$(KN) host lattice. Preliminary single-pass second harmonic generation (SHG) experimental results indicate that there exists marginal improvement in the phase-matching temperature tolerance of KRN compared to that of pure Kn single crystals.

• Korean Journal of Environment and Ecology
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• v.7 no.1
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• pp.1-5
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• 1993

To examine aluminum toxicity on woody plants, aluminum solution and ground water(pH 6.75) were treated on the seeded pot (48$\times$33$\times$9cm) of Pinus thunbergiana, Thuja orientalis and Ligustrum obtusifolium, filled with sand, three times per week, 5mm per time, from April 28, 1993 to June 16. Aluminum solution were prepared 1.0, 2.5 and 5.0mM aluminum potassium sulfate, dilulted with ground water. Growth-related characters(seedling number, seedling height, top, root and total dry weight) were measured and compared among species and treatments. The response of seedling growth-related characters to aluminum solution treatment differed among the species, and the most sensitive species is Ligustrum obtusifolium, and the most tolerant species is Pinus thunbergiana.

• Restorative Dentistry and Endodontics
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• v.24 no.2
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• pp.330-336
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• 1999

In biological systems, the mineral that forms hard tissue is of an apatitic nature, and hydroxyapatite($Ca_5OH(PO_4)_3$: HA) is generally considered as the prototype for such a mineral. Thus, the precipitation of HA, having biological implications, has been the subject of several investigations. Crystal growth studies using HA seeds in supersaturated solutions have enhanced our understanding of the process and mechanism involved in seeded crystal growth. From these studies, it has become apparent that the precipitation rate of HA onto the seed crystals depends on the various conditions, especially on the additives. The relation between the supersaturated solution containing fluoride and the process of HA crystal growth enhances the understanding of mechanism of HA crystal growth. Until recently, the studies have been on the crystal growth of enamel minerals and synthetic HA seeds in the supersaturated solution containing 1~2 ppm fluoride. The purpose of the present investigation is to study the effect that fluoride of high concentration has on the crystal growth kinetics of HA. In order to produce the composition found in the secretory enamel fluid, experimental solutions of 1mM Ca, 3mM P, and 100mM Tris as background electrolyte were used. Then this experimental solutions were added to 0, 2, 4, 6, 8, 10 ppm fluoride. The effect of fluoride at high concentrations on the precipitation was examined in a bench-top crystal growth model adopting a miniaturized reaction column. Chemical analysis was employed for characterization of working solutions before and after the experimentation. Remarkable findings were : 1) the amount of crystal growth was gradually accelerated as the fluoride concentration increased until 6 ppm, but decreased in 8 and 10 ppm fluoride; 2) the amount of fluoride ion consumed in crystal formation was constant despite the increase in fluoride concentration.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.9 no.4
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• pp.396-401
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• 1999

In the present paper, potassium lithium niobate(KLN) crystals have been grown along <001>, <100> and <110> directions by the top seeded solution growth (TSSG) method from Li-richer melts with different compositions. The morphologies of KLN crystals grown along different directions have been studied, and the well-developed facets have been unambiguously indexed using X-ray goniometer and stereographic projection analysis. The growth mechanism and defects such as cracks and inclusions were discussed on the basis of observations of facets on the crystal-solution interfaces. The crystal compositions were determined by a chemical analysis method. The structure and lattice constants of KLN crystals were determined and calculated on the basis of XRD data by using TREOR90 and PIRUM programs. The Curie temperature and optical absorption were determined by dielectric constant peak and spectrum measurements. respectively. The blue second harmonic generation (SHG) characteristics of KLN sample were also investigated using a pulsed dye laser.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.3
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• pp.396-400
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• 1998

The physical properties of KLN single crystals very significantly according to the $Nb_2O_5$ content in grown crystal, therefore, it is very important to control the composition of KLN single crystals. In this study, KLN single crystals of high content $Nb_2O_5$ were grown by temperature fluctuation and TSSG (Top-seeded solution growth) methods with increasing the $Nb_2O_5$ content of starting solution. To investigate the existence of defect due to the increase of $Nb_2O_5$ content, dielectric and optical properties were measured. Due to the increase of defects in grown KLN single crystal, the shift of cutoff-frequency to lower energy and a broad Curie range, which shows the DPT (diffuse phase transition) characteristics, were observed.

• Korean Journal of Crystallography
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• v.14 no.2
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• pp.73-78
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• 2003

(Ba/sub 1-x/Sr/sub x/)TiO₃ (BST, 0.4< x <0.65) single crystals were successfully grown by the TSSG (Top-Seeded Solution Growth) method, using a commercial [100] SrTiO₃ or as-grown [100] BST single crystals as seed crystals. To obtain the BST single crystals with various compositions x, the Ba/sr molar ratios in the solutions were systematically controlled while the Ti ion content among all cations was fixed at 67 mol%. A linear regression curve between their x values and the molar ratios of Sr/(Ba + Sr) in the solutions could be obtained, which in turn could used to select the initial composition to produce BST crystal with an aimed x value. In addition, the isothermal growth was found more effective for obtaining a compositional uniformity than a slow cooling process.