• Progress in Superconductivity and Cryogenics
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• 제21권4호
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• pp.19-23
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• 2019

A large grain YBCO bulk superconductor is fabricated by the top-seeded melt growth (TSMG) method. In the TSMG process, the seed crystal is placed on the top surface of a partially melted compact and therefore the seed crystal is frequently tilted during the melt process due to intrinsic unstable nature of Y211 particle +liquid phase mixture. In this work, we report the successful growth of single-domain YBCO bulk superconductors by a bottom-seeded melt growth (BSMG) method. Investigations on the trapped magnetic field and the microstructures of the synthesized specimens show that a bottom-seeded melt growth method has hardly affected on the crystal growth behavior, the microstructure development and the magnetic properties of the large grain YBCO bulk superconductors. The bottom-seeded melt growth method is clearly beneficial for the stable control of seed orientation through the melt process for the fabrication of a large grain YBCO bulk superconductor.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제5권1호
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• pp.44-49
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• 1995

Abstract The surface of 6H - SiC bulk crystal grown by sublimation process was investigated by optical microscope observation. Since, in the 6H crystal growing, the crystal had the habitual step growth attitude such that the lateral growth rate along the random a - axis orientation was higher than that along the c - axis of the growth direction, then many steps were developed. There were, also, many micropipes on the surface in the form of as-like large voids. However, they were differenciated with pores and cross- sectional shape of them were close to the circle. In this study, many micropipes, planar defects and the growth steps appeared on the grown crystal surface were investigated.

• Journal of the Korean Crystal Growth and Crystal Technology
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• 제4권1호
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• pp.57-62
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• 1994

$YbFeCoO_4$ single crystal was grown by floating zone method. The atmospheric condition of the growth was controlled in air and the growth rate was 1~2 mm/hr. After melting the feed rod of the composition of $YbFeCoO_4$, $YbFeCoO_4$ was decomposed to $YbFeCoO_4$ and CoO phase in the initial state of the growth. The liquid composition, however, changed to the direction of the eutectic point along the liquidus line and then stopped at the point in which $YbFeCoO_4$ single crystal could be grown. The growth direction of the crystal was preferred orientation [110], perpendicular to the c-axis in the hexagonal system due to using the polycrystalline seed.

• Proceedings of the KIEE Conference
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• 대한전기학회 1995년도 하계학술대회 논문집 C
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• pp.1245-1247
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• 1995

In this paper, Analyzed structual property using SEM and XRD. The longer distance between substrate and target enhance crystalographic orientation of (110)plane, but inhibit growth of (002)plane. Also, deposited ZnO thin film on electrode layer inhibit crystalographic orientation of (002)plane, expecially Al electrode inhibit stronger than Pt layer. And using fabricated transducer, analyzed eletric and frequency characteristics.

• Journal of the Korean Vacuum Society
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• 제8권3B호
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• pp.333-339
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• 1999

$RuO_2$ thin films were prepared with various deposition conditions by rf magnetron sputtering. The films were annealed in vacuum, air, and air-vacuum, after that, the structural and electrical properties of the films were investigated. As the substrate temperature increases, the preferred orientation of the films changes from (101) to (200), and the grain size increases; especially, at $500^{\circ}C$, the size considerably increases. The preferred orientation of the films changes from (200) to (101) and the roughness of surface increase with the increase in oxygen partial pressure. The lowest value of resistivity of $RuO_2$ we prepared is $1.5\times 10^{-5}\Omega\codt\textrm{cm}$ at the conditions of $400^{\circ}C$ and 10% of oxygen partial pressure. After the processes of annealing, the films deposited at $400^{\circ}C$ and a oxygen partial pressure of 10% were relatively stable. The films deposited at $500^{\circ}C$ have denser structure and smoother surface when the films are annealed in vacuum after annealing in air.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 한국소성가공학회 2000년도 추계학술대회 논문집
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• pp.70-73
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• 2000

A finite element analysis model is suggested for analysis of forming process of milli structure whose size is from a few hundreds ${\mu}m$ to a few mm. In this paper, finite element formulation which assemble crystal plasticity theory considering texture development with damage mechanics is developed, since orientation development and growth of micro voids became the primary factors for deformation aspects in large deformation of milli structure. Applying to, extremely, extrusion process of single crystal and extrusion/drawing process of polycrystal milli-size bar, extrusion force, preferred orientation, and damage evolution are examined to understand the characteristics of deformation of milii-size bar.

• Applied Microscopy
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• 제24권4호
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• pp.123-131
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• 1994

In this study the initial stage nucleation and growth of Ni silicide on (001) Si by evaporation and furnace annealing have been investigated by transmission electron microscopy. The pressure was $10^{-6}$ Torr during evaporation and annealing. And the annealing temperature to produce $NiSi_2\;was\;800^{\circ}C$. From the evaporated film, $NiSi_2$ nucleus has grown into Si substrate with an epitaxial orientation relationship. Interfaces between $NiSi_2$ and Si were A-type {111} interfaces and {100} $NiSi_2$ interfaces were also observed at the initial stage of nucleation. Ni silicide grew into Si substrate, but the nucleus partly grew into the evaporated film, with no facets, from the nuclei in the Si substrate. $NiSi_2$ nucleus with (111) habit planes was also observed.

• Journal of the Korean institute of surface engineering
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• 제18권2호
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• pp.53-60
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• 1985

The microstructure of zine electrodeposits was investigated by using zinc sulfate solution in still bath. The cathode current efficiency decreased with increasing current density, and decreasing temperature. The preferred orientation of the zinc electrodeposits changed from (10.3) texture to(10.${\ell}$)-(00.1)(${\ell}$=1, 2, 3) texture through (10.2)-(10.3) preferred orientation with increasing cathode over potential. The surface morphology of zinc electrodeposits changed from the dendritic growth with granular crystallites to the blocks of hexagonal crystallites packed together with increasing current density. The microstructure of cross section of the above deposits are the rough granular structure and columnar structure respectively.

• Journal of the Korean institute of surface engineering
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• 제32권3호
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• pp.401-405
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• 1999

Reflective silver films with high quality were prepared on polyester substrate by using sputter deposit on techniques. Best reflectivity thin films of silver were produced with process parameters of $10^{-6}$ Torr as base pressure, 50 W as R.F. power, 5 mTorr as working pressure, and 10 sccm as Ar flow rate. Being deposited with an R.F. power of 50 W, Ag films revealed the highest 96.3 % reflectance as illuminated with a light of 700 nm wavelength. The adhesion of sample films showed as high as 14 to $20{\;}kg/\textrm{cm}^2$, which is suitable for industrial purposes. Their film crystallinity and orientation resulted in the planes of (111) and (200) for the growth with a preferred orientation of <111>, in general. The cross-sections of thin film specimens showed columnar structures. It is noted that columns became coarsened and less dense as R.F. power increased, resulting in a low reflectivity for the product film.

• Progress in Superconductivity and Cryogenics
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• 제24권3호
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• pp.52-56
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• 2022

Single-grain (c-normal or c-parallel) and multi-grain YBCO superconductors were prepared by a melt growth process with/without seeding. The magnetic levitation force and trapped magnetic field at liquid N₂ temperature (77 K) of the YBCO superconductors were investigated. Samples for the levitation force measurement were zero-field cooled (ZFC) to 77 K, and samples for trapped field measurement were field-cooled (FC) using Nd magnets. As for the magnetic levitation force, the c-normal, single grain sample showed the largest value, whereas the multi-grain sample showed the lowest value. The trapped magnetic field of the c-normal and c-parallel single-grain samples was 4-5 times that of the multi-grain sample. In addition, as the external magnetic field (the number of magnets) increased, the both properties increased proportionally. These results were explained in terms of the orientation dependence of the levitation forces and the magnetic field trapping capability of the YBCO superconductor.