• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.343-350
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• 2003

Using Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ powders prepared by solid state reaction and spray drying method, the nucleation and growth behaviors of superconducting and second phases were investigated during isothermal heat treatment. When the spray drying power was used in contrast with solid state reaction powder, Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2223) phase could be formed at the relatively shot time and second phases were much bigger. Quantitative analysis showed that as the heat treatment time increased, more Bi$_2$Sr$_2$Ca$_2$.$_2$Cu$_3$ $O_{x}$ (2212) changed to 2223 and the major second phase was changed from (Sr,Ca)$_{14}$Cu$_{24}$ $O_{x}$(14:24) to (Sr,Ca)$_2$Cu$_1$ $O_{x}$ (2:l). The superconducting phase formed at the relatively short time 14:24 phase. Following the Bi-free phase of 14:24 Phase, but long time was needed in places far from the 14:24 phase. Following the formation of the 2212 phase near the 14:24 phase, the 2223 phase nucleated preferentially at the interface between the 2212 and 14:24 phases. The preferential nuclcation of 2223 was explained by its structural similarity and low Interfacial energy with both the Bi-free and 2212 Phases.12 Phases.

• Bulletin of the Korean Chemical Society
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• v.12 no.6
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• pp.606-612
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• 1991

We have carried out an extended Huckel calculation to rationalize the role of $CuO_3$ chains and the size effect of the charged model clusters for the following charged model culsters : ${{Cu_6}{O_{21}}^{28-},\;{{Cu_6}{O_{22}}^{30-}\;,{{Cu_9}{O_{30}}^{39-}\;,{{Cu_9}{O_{32}}^{43-}\;,{{Cu_{12}{O_{38}}^{48-}\;,{{Cu_{15}{O_{50}}^{65-}\;,{{Cu_{18}{O_{54}}^{66-}\;,{{Cu_{18}{O_{55}}^{68-}\;,{{Cu_{24}{O_{70}}^{84-}\;and\;{{Cu_{27}{O_{78}}^{93-}$ for high-$T_c$ superconductor $YBa_2Cu_3O_7$: ${{Cu_6}{O_{18}}^{22-}\;,{{Cu_9}{O_{26}}^{31-}}\;,{{Cu_{12}{O_{32}}^{36-}\;,{{Cu_{15}{O_{42}}^{49-}\;,{{Cu_{18}{O_{46}}^{50-}\;,{{Cu_{24}{O_{60}}^{64-}\;and\;{{Cu_{27}{O_{66}}^{69-}$ for insulator $YBa_2Cu_3O_6$. The results show that the electronic structures and properties of the charged model clusters relating to high-$T_c$ superconductor are very sensitive to the size change of the clusters with various environmental effects, wherease those of the charged model clusters for insulator $YBa_2Cu_3O_6$ are monotonous to the size change. The $CuO_3$ chains along the b-direction may yield cooperative electronic coupling with the $CuO_2$ layers in determining both conducting and superconducting properties of $YBa_2Cu_3O_{7-x}$ system.

• Proceedings of the Korea Crystallographic Association Conference
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• 2003.05a
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• pp.24-24
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• 2003

고온초전도 BSCCO 2223 ((Bi, Pb)₂Sr₂Ca₂Cu₃O/sub x/) 선재의 특성을 향상시키기 위해서는 반복적인 인발 및 압연과정을 통한 texturing향상, BSCCO 2223입자의 배향성 증대, 피복재내 초전도체의 충진율(밀도)향상, 이차상의 부피분율 감소등이 이루어져야 한다. 최적 열처리 조건을 통하여 열처리 시에 형성되는 이차상인 (Bi,Pb)₂Sr₂CuO/sub y/ (2201, amorphous phase)를 조절하면서, (Ca,Sr)₂CuO₃ (2/1 AEC), (Ca,Sr)/sub 14/Cu/sub 24/O/sub 41/ (14/24 AEC)와 같은 이차상들의 부피분율 및 크기를 감소시켜야만 한다. 본 실험에서는 BSCCO 2223 선재의 특성을 향상시킬수 있는 최적의 열처리 조건 확립 및 기계적 공정시 나타나는 여러 가지 문제점을 개선하여 높은 임계전류를 가지는 선재의 특성을 분석하고자 하였다. 최종적으로 제조된 선재는 2223상 결정이 피복재(Ag)와 평행하게 길게 성장하며, AEC상의 크기와 부피분율이 감소할수록 더 높은 임계전류특성을 나타내었다(I/sub c/～70A, J/sub c/～42,000 A/㎠). 또한 이 선재에서 나타나는 여러 가지 이차상들을 분석하기 위하여 XRD, SEM, EDS 분석을 행하였다.

• Korean Journal of Materials Research
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• v.24 no.1
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• pp.19-24
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• 2014

We report the nitrogen monoxide (NO) gas sensing properties of p-type CuO-nanorod-based gas sensors. We synthesized the p-type CuO nanorods with breadth of about 30 nm and length of about 330 nm by a hydrothermal method using an as-deposited CuO seed layer prepared on a $Si/SiO_2$ substrate by the sputtering method. We fabricated polycrystalline CuO nanorod arrays at $80^{\circ}C$ under the hydrothermal condition of 1:1 morality ratio between copper nitrate trihydrate [$Cu(NO_2)_2{\cdot}3H_2O$] and hexamethylenetetramine ($C_6H_{12}N_4$). Structural characterizations revealed that we prepared the pure CuO nanorod array of a monoclinic crystalline structure without any obvious formation of secondary phase. It was found from the gas sensing measurements that the p-type CuO nanorod gas sensors exhibited a maximum sensitivity to NO gas in dry air at an operating temperature as low as $200^{\circ}C$. We also found that these CuO nanorod gas sensors showed reversible and reliable electrical response to NO gas at a range of operating temperatures. These results would indicate some potential applications of the p-type semiconductor CuO nanorods as promising sensing materials for gas sensors, including various types of p-n junction gas sensors.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.25-28
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• 2022

We investigated the formation of superconducting intergrowth phases through the interface reaction both between TlSr₂Cu₁O₅ (Tl-121) and (CrO₄)Sr₂CuO₂, and between Tl -121 and ((CO₃)_0.5(CrO₄)_0.5 Sr₂CuO₂ phases. We found oxychromate intergrowth phases can be formed through the interface reactions and a new superconducting oxychromate compound TlSr₄Cu₂O_z(CO₃)_0.5(CrO₄)_0.5 with T_c above 73 K was discovered based on the results of the interface reactions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.870-875
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• 2011

The $(Na_{0.52}K_{0.44})(Nb_{0.9}Sb_{0.06})O_3-0.04dLiTaO_3$ (NKNS-LT) ceramics with various $Cu_2O$ concentration were prepared by the conventional solid state reaction method. The $Cu_2O$ content was varied in the range of 0.1~0.4 wt%. The effects of Cu on microstructure, crystallographic phase transition, and piezoelectric properties were investigated. The material with perovskite structure had a tetragonal phase (T1) when $Cu_2O$ concentration was less than 0.3 wt% and it transformed to another tetragonal phase (T2) when the $Cu_2O$ amount was greater than 0.3 wt%. The phase boundary between T1 and T2 phases appeared at around 0.3 wt% of $Cu_2O$ concentration. The piezoelectric properties were shown the maximum values at the composition of the phase boundary. The electro-mechanical coupling factor ($k_p$) was 0.42 and the piezoelectric charge constant ($d_{33}$) was 245 pC/N at the 0.3 wt% of $Cu_2O$ concentration.

• Journal of the Microelectronics and Packaging Society
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• v.24 no.2
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• pp.37-41
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• 2017

Cuprous oxide ($Cu_2O$) is one of the potential candidates as an absorber layer in ultra-low-cost solar cells. $Cu_2O$ is highly desirable semiconducting oxide material for use in solar energy conversion due to its direct band gap ($E_g={\sim}2.1eV$) and high absorption coefficient that absorbs visible light of wavelength up to 650 nm. In addition, $Cu_2O$ has other several advantages such as non-toxicity, low cost and also can be prepared with simple and cheap methods on large scale. In this work, we deposited the $Cu_2O$ thin films by electrodeposition on gold coated $SiO_2/Si$ wafers. We changed the process conditions such as pH of the solution, applied potential on working electrode, and solution temperature. Finally, we confirmed the structural properties of the thin films by XRD and SEM.

• Progress in Superconductivity and Cryogenics
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• v.24 no.4
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• pp.16-24
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• 2022

Applications of REBa₂Cu₃O_7-δ tapes require joints with a simple manufacturing process, low resistance and good mechanical properties. In the present study, we successfully developed a copper diffusion joint between Cu-stabilized REBa₂Cu₃O_7-δ tapes that meets the above requirements without solder simply by applying flux, heat and pressurization. After a 3 min thermocompression process at approximately 150 δ and 336 MPa in air, two tapes were directly connected between Cu stabilizers by copper diffusion, which was proven by microstructure analysis. The specific resistivity of the copper diffusion joint reached 5.8 nΩ·cm² (resistance of 0.4 nΩ for a 306 mm splicing length) at 77 K in the self-field. The axial tensile stress reached 200 N without critical current degradation. The results show promise for the preparation of copper diffusion joints to be used in coils, attached tapes, and wire/cable terminals.

• Proceedings of the Materials Research Society of Korea Conference
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• 1994.05a
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• pp.24-25
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• 1994

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.3
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• pp.193-199
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• 2013

In this work, thin film type Cu/ZnO nanostructure catalysts were fabricated by several synthetic routes in order to maximize the performance of the micro reforming system. For this work, various Cu/ZnO nanostructure catalysts could be synthesized by means of four approaches which are chemical vapor method, wet solution method and their hybrid method. The reforming performance of these as-synthetic catalysts was evaluated as compared to the conventional catalysts. Among the as-synthetic nanostructures, sphere type catalysts with specific surface of $18.6m^2/g$ showed the best performance of hydrogen production rate of 30ml/min at the feed rate of 0.2ml/min. This work will give the first insight on thin film type Cu/ZnO nanostructure catalyst for micro reforming system for hydrogen production of portable electronic systems.