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pISSN : 1225-1429 / eISSN : 2234-5078

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2022, Vol.32, No.4

  • 1.

    Spatial variation in quality of Ga2O3 single crystal grown by edge-defined film-fed growth method

    Su-Bin Park , Tae-Wan Je , Hui-Yeon Jang and 6 other persons | 2022, 32(4) | pp.121~127 | number of Cited : 0
    Abstract PDF
    β-Gallium oxide (Ga₂O₃), an ultra-wide bandgap semiconductor, has attracted great attention due to its promising applications for high voltage power devices. The most stable phase among five different polytypes, β-Ga₂O₃ has the wider bandgap of 4.9 eV and higher breakdown electric field of 8 MV/cm. Furthermore, it can be grown from melt source, implying higher growth rate and lower fabrication cost than other wide bandgap semiconductors such as SiC, GaN and diamond for the power device applications. In this study, β-Ga₂O₃bulk crystals were grown by the edge-defined film-fed growth (EFG) process. The growth direction and the principal surface were set to be the [010] direction and the (100) plane of the β- Ga₂O₃ crystal, respectively. The spectra measured by Raman analysis could exhibit the crystal phase and impurity doping in the β-Ga₂O₃ ingot, and the crystallinity quality and crystal direction were analyzed using high-resolution X-ray diffraction (HRXRD). The crystal quality and various properties of as-grown β-Ga₂O₃ ribbon was systematically analyzed in order to investigate the spatial variation in entire crystal grown by EFG method.
  • 2.

    A study on the calcination process of synthetic silica powder for quartz glass crucibles

    Jae-Kyo Yang , Yun-Ho Jin | 2022, 32(4) | pp.128~135 | number of Cited : 0
    Abstract PDF
    The inside of a quartz glass crucible for semiconductor processing, called a transparent layer, is manufactured using synthetic silica powder. Bubbles existing in the transparent layer of the crucible cause a problem of reducing the quality of the crucible as well as the yield of the silicon ingot. Therefore, the main goal of the synthetic silica powder, which is the raw material of the transparent layer, is to minimize the bubble generation factor. For this purpose, in the case of synthetic silica powder, it is necessary to minimize silanol groups, carbon and pores. In this study, synthetic silica gel was prepared using the sol-gel method, and changes in carbon content and specific surface area were investigated according to calcination temperature and dwelled time in a two-stage calcination process. The first-stage calcination process was performed between 500°C and 600°C and the second-stage calcination process was performed between 1000°C and 1100°C. The dwelled time was carried out from 10 minutes to a maximum of 12 hours. The carbon content of the powder calcined at 1000°C for 1 hour was 0.0031 wt.%, and the specific surface area of the powder calcined at 1100°C for 12 hours was 16.6 m²/g.
  • 3.

    The effect of Dy2O3 addition on crystal structure, grain growth, and dielectric properties in BaTiO3

    Won-Gi Ahn , Moonhee Choi , Minkee Kim and 1 other persons | 2022, 32(4) | pp.136~142 | number of Cited : 0
    Abstract PDF
    The crystal structure, grain growth behavior, and dielectric properties of BaTiO3 have been studied with the addition of Dy2O3. The powders were synthesized at ratios of (100-x)BaTiO3-xDy2O3 (mol%, x = 0, 0.5, 1.0, 2.0) by a conventional solid-state synthesis, and the powder compacts were sintered at 1250°C for 2 hours in air. As the amount of added Dy2O3 was increased, the crystal structure of the sintered samples changed from a tetragonal to a pseudo-cubic structure, and the tetragonality decreased. In addition, a secondary phase of Ba12Dy4.67Ti8O35 appeared when Dy2O3 was added. The average grain size after sintering decreased and abnormal grains appeared as the amount of Dy2O3 increased. It can be explained that the grain growth behavior of the Dy2O3 added-BaTiO3 occurs due to the two-dimensional nucleation and growth, and is governed by the interface reaction. Further, the correlation between crystal structure, microstructure, and dielectric properties was discussed.
  • 4.

    Property of geopolymers with aluminum smelting waste

    kimhakmin , KIM, YOOTAEK | 2022, 32(4) | pp.143~150 | number of Cited : 0
    Abstract PDF
    Geopolymers were made by mixing IGCC slag and aluminum smelted waste and their properties were compared with those of IGCC slag based geopolymers. When two raw materials were mixed, the highest compressive strength was obtained at 1.78 of Si/Al ratio. Because the change in compressive strength and density was not so sensitive by the change in Si/Al ratio; that is, the permissible range of Si/Al ratio mixing ratio is broad, it was speculated this broad permissible range would be advantageous for commercialization. The Compressive strength of geopolymers including red mud was higher than that of IGCC based ones and the safety was confirmed by TCLP test. Therefore, it was concluded that the making geopolymers by mixing red mud not only enhances the properties of geopolymers but also gives a recyclability as safe construction materials.
  • 5.

    Analysis of carbonation characteristics on waste concrete

    Nam-Il Kim , Jong Tae Lee , Chu Yong-Sik | 2022, 32(4) | pp.151~158 | number of Cited : 0
    Abstract PDF
    In this study, the waste concrete sample obtained as various particle size (0~2.36 mm) was carried out the basic measurements and carbonation for analyzing the possibility of its carbonation. It was then investigated some analysis such as crystallization (XRD pattern), microstructure (SEM), and the production of CaCO3 through the ignition loss (TG-DTA). The content of CaCO3 in the waste concrete sample before carbonation was found in 14.51 % and 28.52 % after carbonation in 24 hours. Moreover, the content of CaCO3 carbonated in 24 hours with fine grinded waste concrete sample was 32.73 %. The carbonation of the waste concrete sample was rapidly performed up to 6 hours, but gradually increased from 12 to24 hours. Especially, the amount of CaCO3 between 12 and 24 hours was only produced 2.32 %. The calcite-shaped CaCO3 crystals after carbonation of the waste concrete sample were found in microstructure and their peaks were strongly detected on XRD pattern.
  • 6.

    Current status of gem-quality laboratory-grown diamond

    Hyun-Min Choi , Young-Chool Kim , Jeong-Won Seok | 2022, 32(4) | pp.159~167 | number of Cited : 0
    Abstract PDF
    In the past few decade years, laboratory-grown diamonds, also known as synthetic diamonds usually, have become more and more prosperous in the global diamond market. There are two main crystal growth processes of the gem-quality laboratory-grown diamond, the high pressure and high temperature (HPHT) and chemical vapor deposition (CVD). Synthetic gem diamonds grown by the HPHT press have been commercially available since the mid-1990s. Today, significant amounts of gem-quality colorless HPHT laboratory-grown diamonds have been producing for the jewelry industry. In the last several years, the CVD laboratory-grown diamonds have been gaining popularity in the market. In 2021, the CVD production rose and there are expectations that the trend would move upward continuously. This article presents information about the current status of laboratory-grown diamonds, lower cost compared to natural diamonds, market share, color distribution, spectroscopic properties of laboratory-grown diamonds, and so on.