MgB₂ 초전도체

송규정 ( Kyu Jeong Song ) 전북대학교 과학교육연구소 2017 과학과 과학교육 논문지 Vol.42 No.1

MgB₂ 초전도체는 중간금속성 초전도체이다. 2001년 처음으로 MgB₂ 물질에서 초전도성이 발견된 후, 지금까지 17년 동안 MgB₂ 초전도체에 대하여 수많은 연구들이 진행되었다. 초전도메커니즘 규명을 위한 MgB₂ 초전도특성 연구들이 수행되어, 기존의 저온 및 고온초전도체의 특성들과 구별되는 MgB₂ 고유의 초전도특성들이 발견되었고, 또한 산업적인 응용을 위한 MgB₂ 초전도선재 연구들이 수행되어, 경제적인 MgB₂ PIT(powder in tube) 초전도선재들이 개발되었다. 현재, MgB₂ 초전도체는 초전도연구의 핵심 분야로서 한 부분을 차지하고 있으며, MgB₂ 초전도특성 향상과 MgB₂ 초전도마그넷처럼 MgB2 PIT 초전도선재의 초전도전력기기 응용을 위해 많은 연구자들이 활발히 참여하고 있다. 따라서 아직도 많은 연구자들의 관심 속에 있는 MgB₂ 초전도체의 본 리뷰 논문에서는 저자가 지금까지 수행해온 MgB₂ 초전도관련 연구 결과들을 중심으로 MgB₂ 초전도체의 최근 연구동향들과 미래 연구경향들을 논의하고자 한다. The MgB₂ superconductor is an inter-metallic superconductor. Since the discovery of superconductivity in MgB₂ materials in 2001, a number of studies have been conducted on MgB₂ superconductor for 17 years. MgB₂ superconductivity studies have been carried out to elucidate the superconducting mechanism. MgB₂ inherent superconducting properties are differentiated from those of conventional low-Tc and high-Tc superconductors. For industrial applications, MgB₂ superconducting wire has been developed, and economical MgB₂ PIT superconducting wires have been commercialized. In these days, the MgB₂ superconductor is one of the core fields in superconducting area. Many researchers vigorously participate in the fields of the enhancement of MgB₂ superconductivity and the MgB₂ superconducting power application, such as MgB₂ superconducting magnet. Therefore, on the basis of MgB₂ superconductivity studies performed by the present author on MgB₂ superconductor, recent research trends and future research trends of MgB₂ superconductors, which are in the interest of many researchers, will be discussed in this review paper.

PPMS 기기를 이용한 물질의 자기적 특성 실험

양정훈 ( Jeong Hun Yang ),유종수 ( Jong Su You ),송규정 ( Kyu Jeong Song ) 전북대학교 과학교육연구소 2021 과학과 과학교육 논문지 Vol.46 No.2

물질의 물성을 측정하는 기기는 다양하다. 본 논문은 초전도 물질의 전기적 및 자기적 특성들을 측정하는 Quantum Design의 PPMS system을 소개하고, 이를 이용한 실험방법 및 분석방법 등을 서술하였다. 본 연구실에서 PPMS-DC 비저항(resistivity) system 혹은 PPMS-VSM 마그네토미터(magnetometer) Option 등을 이용하여 수행했던 초전도 물질들에 대한 기본적인 초전도 물리량들의 특성평가 및 분석방법 등을 서술하였다. There are many instruments that measure the physical properties of matter. This paper introduces the PPMS system of Quantum Design, which measures electrical and magnetic properties of matter including superconducting materials, and describes the experimental methods and analysis methods using the PPMS system. In this paper, both results and analyses of the characteristics of the basic superconducting physical quantities of superconducting materials performed, by employing the PPMS-DC resistivity system or the PPMS-VSM magnetometer options, in our laboratory were described.

Fabrication of High-Quality $SmBa_{2}Cu_{3}O_{7-{\delta}}$ Thin Films by a Modified TFA-MOD Process

김덕진,송규정,문승현,박찬,유상임,Kim Duck-Jin,Song Kyu-Jeong,Moon Seung-Hyun,Park Chan,Yoo Sang-Im The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1

We report a successful fabrication of high-quality $SmBa_{2}Cu_{3}O_{7-{\delta}}$ (SmBCO) thin films on $LaAlO_3$(LAO)(100) single crystalline substrates by a modified TFA-MOD method. After the pyrolysis heat treatment of spin-coated films up to $400^{\circ}C$, SmBCO films were fired at various temperatures ranging from 810 to $850^{\circ}C$ in a reduced oxygen atmosphere (10 ppm $O_2$ in Ar). Optimally processed SmBCO films exhibited the zero-resistance temperature ($T_{c,zero}$) of 90.2 K and the critical current density ($J_c$) of $0.8\;MA/cm^2$ at 77K in self-field. Compared with the $J_c$ values (normally, > $2\;MA/cm^2$ at 77 K) of MOD-TFA processed YBCO films, rather depressed $J_c$ values in SmBCO films are most probably attributed to the existence of ${\alpha}$-axis oriented grains.

전자기 유도를 이용한 자석의 자화도 측정 연구

이정우 ( Jeong Woo Lee ),이사랑 ( Sa Rang Lee ),송규정 ( Kyu Jeong Song ) 전북대학교 과학교육연구소 2020 과학과 과학교육 논문지 Vol.45 No.1

본 연구에서 우리는 전자기 유도(Electromagnetic induction) 현상을 이용하여 영구자석(Permanent magnet)의 자화도(Magnetization) M 을 측정하였다. 솔레노이드(Solenoid) 코일다발(Coil bundle)의 중심축을 따라 자유낙하 운동하는 영구자석에 의한 자속(Magnetic flux) 변화는 코일다발에 전자기 유도 현상을 일으킨다. 이와 같이 발생하는 전자기 유도 현상을 분석하여 영구자석의 자화도 M 을 예측하였다. 최고점 유도 기전력(Maximum induced electromotive force) ε_max 에 대한 영구자석의 자기쌍극자 모멘트(Magnetic dipole moment) 평균값 m₊(αυg)은 3.2666 Am² 이고, 자화도 M은 3.33×10⁵ A/m 이며, 자기장의 세기 μ₀M은 0.42 T = 42000 G로 예측되었다. 이 결과는 테슬라미터(Tesla meter)를 이용하여 얻은 결과들과 약 10% 오차 내에서 일치하였다. In this study we measured the magnetization M of permanent magnets by using electromagnetic induction. Magnetic flux changes by permanent magnet that does free falling along the central axis of a solenoid coil cause electromagnetic induction in a coil bundle. The magnetization M of the permanent magnets was estimated by analyzing the electromagnetic induction phenomenon. The magnetic dipole moment average value m₊(αυg) of the permanent magnet for induced electromotive force ε_max at the maximum position is 3.2666 Am², the magnetization M ≃ 3.33 × 10⁵ A/m , and the magnetic field intensity μ₀M ≃ 0.42 T = 4200 G. These results were consistent with the results obtained using a Tesla meter within about 10% of the error.

초전도 테이프 제작을 위한 니켈기판 상의 산화물 박막 증찰

김호섭,고락길,정준기,하홍수,송규정,박찬,Kim, Ho-Sup,Shi, Dongqui,Ko, Rock-Kil,Chung, Jun-Ki,Ha, Hong-Soo,Song, Kyu-Jeong,Park, Chan 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.12

High temperature superconducting coated conductor has a structure of <protecting layer>/<superconducting layer>/<buffer layer>/<metallic substrate>. The buffer layer consists of multi-layer, this study reports the deposition method and optimal deposition conditions of YSZ(Yttria-stabilized zirconia) layer which plays a important part in preventing the elements of substrate from diffusing into the superconducting layer. YSZ layer was deposited by DC reactive sputtering technique using water vapor for oxidizing deposited elements on substrate. To investigate optimal thickness of YSZ film, four YSZ/CeO$_2$/Ni samples with different YSZ thickness(130 nm, 260 nm, 390 nm, and 650 nm) were prepared. The SEM image showed that the surface of YSZ layer was getting to be rougher as YSZ layer was getting thicker and the growth mode of YSZ layer was columnar grain growth. After CeO$_2$ layer was deposited with the same thickness of 18.3 nm on each four samples, YBCO layer was deposited by PLD method with the thickness of 300 nm. The critical currents of four samples were 0, 6 A, 7.5 A, and 5 A respectively. This shows that as YSZ layer is getting thicker, YSZ layer plays a good role as a diffusion barrier but the surface of YSZ layer is getting rougher.

RABiTS 위에 PLD 방법으로 증착된 YBCO 초전도 박막 선재의 제조

고락길,정준기,하홍수,김호섭,송규정,박찬,문승현,유상임,김영철,Ko Rock-Kil,Shi Dongqi,Chung Jun-Ki,Ha Hong-Soo,Kim Ho-Soup,Song Kyu-Jeong,Park Chan,Moon Seung-Hyun,Yoo Sang Im,Kim Young-Cheol 한국초전도학회 2004 Progress in superconductivity Vol.6 No.1

YBCO coated conductor is one of the most promising materials as a new generations wire especially for practical power applications. In this work, $YBa_2$$Cu_3$$O_{7}$ -$\delta$/(YBCO) coated conductors (CC) were deposited by pulsed laser deposition (PLD) from buffer layers to superconducting layer on hi-axially textured metal tape. The oxide multilayer buffered substrate of architectures of $CeO_2$/$YSZ/Y_2$$O_3$ was fabricated by PLD at steady status. Then YBCO layer was deposited on RABiTS substrate by stationary and reel-to-reel (R2R) continuous process and we compared with deposition conditions of both processes. The degree of texture of each layer was investigated using X-ray diffraction including $\theta$-2$\theta$ scans, $\omega$-scans and $\Phi$-scans analysis. Their surface morphology was observed by scanning electron microscopy (SEM). The FWHM of the X-ray $\Phi$-scans and $\Phi$-scans indicated that YBCO and buffer layers closely replicate the in-plane and out-of-plane texture of metal tape. Critical current (Ic) at 77 K, self-field of 75.8 A/cm-width, critical temperature (Tc) of 85 K, and critical current density (Ic) of 3.7 MA/$\textrm{cm}^2$ were measured from coated conductor deposited by stationary process. And coated conductor deposited by R2R continuous process had Ic of 57.5 A/cm-width, Tc of 86.5 K and Jc of 2.0 MA/$\textrm{cm}^2$. The film also exhibits a homogeneous and dense surface morphology.

연속 공정 PVD 방법에 의한 Coated Conductor 제조

고락길,정준기,김호섭,하홍수,송규정,박찬,유상임,문승현,김영철,Ko, Rock-Kil,Chung, Jun-Ki,Kim, Ho-Sup,Ha, Hong-Soo,Shi, Dongqi,Song, Kyu-Jeong,Park, Chan,Yoo, Sang-Im,Moon, Seung-Hyun,Kim, Young-Cheol 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.11

Continuous physical vapor deposition (PVD) method is one of many processes to fabricate long length coated conductor which is required for successful large-scale application of superconducting power devices. Three film deposition systems (pulsed laser deposition, sputtering, and evaporation) equipped with reel-to-reel(R2R) metal tape moving apparatus were installed and used to deposit multi-layer oxide thin films. Both RABiTS and IBAD texture templates are used. IBAD template consists of CeO$_2$(PLD)/YSZ(IBAD) on stainless steel(SS) metal tape, and RABiTS template has the structure of CeO$_2$/YSZ/Y$_2$O$_3$ which was continuously deposited on Ni-alloy tape using R$_2$R evaporation and DC reactive sputtering in a deposition system designed to do both processes. 0.4 m-long coated conductor with Ic(77 K) of 34 A/cm was fabricated using RABiTS template. 0.5 m and 1.1 m-long coated conductor with Ic(77 K) of 41 A/cm and 26 A/cm were fabricated using IBAD template.

출입문 자동폐쇄장치에 관한 연구

장은석 ( Eun Seok Jang ),송규정 ( Kyu Jeong Song ) 전북대학교 과학교육연구소 2019 과학과 과학교육 논문지 Vol.44 No.1

본 연구에서 주거 또는 상업 건물에서 화재가 번지는 것을 막기 위한 출입문 자동폐쇄장치를 간단히 모델링하였다. 모델링한 장치에는 문을 자동으로 닫히게 하는 스프링과 문이 닫힐 때 속도를 줄이기 위한 저항 장치로 구성 되어있다. 문의 열림 각도에 따라 비틀림 용수철에 의한 힘(torsional spring force)과 장치 내의 감쇠력(damping force)의 차이가 문의 닫힘 속도로 나타나는 시스템으로 모델링하여, 문 닫힘 시 운동방정식 정립 및 해석하였다. 이때 장치는 2차-감쇠 계(second order-damping system), 그리고 장치 내 유체는 비압축성 점성 유체로 가정하였다. An auto-door closer, which is one of the automatic door-closing apparatuses, has been widely used to prevent fire propagations in living or commercial buildings. The auto-door closer consists of a spring to accumulate power for closing a door and a damper to control door-closing velocity. To predict and optimize the temporal door behavior during the door-closing period, the auto-door closing system was modeled as a second order-damping system. And a damping coefficient of the oil damper was also theoretically modeled by analyzing Newtonian, incompressible, viscous flow through an oil passage between an oil control rod and an oil piston body.

홀 계수 측정을 통한 여러 물리량들의 자기적 특성

표성국 ( Seong Guk Pyo ),정다원 ( Da Won Jeong ),송규정 ( Kyu Jeong Song ) 전북대학교 과학교육연구소 2020 과학과 과학교육 논문지 Vol.45 No.1

대부분 대학 실험실에 구축되어 있는 홀 효과(Hall effect) 실험기기를 이용하여, 홀 계수(Hall coefficient) R_H 측정과 부호를 확인하는 실험과정 이외에 홀 계수 R_H, 전하운반자 밀도(Charge carrier density) n, 전하운반자 이동도(Charge carrier mobility) μ 등의 여러 물리량들의 자기적 특성을 조사하였다. 자기장 B 혹은 전류 I을 고정하는 두 방법으로 n형 GaAs 반도체 시편의 홀 계수 R_H 값들을 측정하여 서로 일치함을 확인하였으며, 비저항(Resistivity) p 와 전기전도도(Electric conductivity) σ 값들이 상온에서 각각 1.272×10^-3 V·m/A와 782.6 A/(V·m)임을 예측하였다. 홀 계수 R_H 결과와 전기전도도 σ 결과들을 이용하여, n형 GaAs 시편의 전하운반자 이동도 μ 값들을 구하고, 자기장 B 값이 0일 때, n형 GaAs 시편의 상온에서 전하운반자 이동도 μ ≈ 1.0m²/(V·s) 값을 예측하였다. 본 논문에서 우리는 실험을 통해 데이터를 얻어 분석하고 논의하는 연구과정의 기초를 학부 학생들에게 제공하고자 하였다. Using Hall effect experimental devices of general university laboratories, in addition to the measurement of Hall coefficient R_H and its sign verification, the magnetic characteristics of various physical quantities such as Hall coefficient R_H, charge carrier density n, and charge carrier mobility μ were investigated. The Hall coefficient R_H values of the n-type GaAs semiconductor specimen were measured by two methods of fixing the magnetic field B or current I and were confirmed the same their values. Its resistivity p and electric conductivity σ values were predicted to be 1.272×10^-3 V·m/A and 782.6 A/(V·m) at room temperature, respectively. The charge carrier mobility μ values of the n-type GaAs specimen were obtained using the Hall coefficient R_H results and the electric conductivity σ results, and when the magnetic field B was 0, its charge carrier mobility μ ≈ 1.0 m²/(V·s) value was predicted at room temperature. In this paper, we wanted to provide the foundation of the research process obtaining, analyzing, and discussing for data through an experiment, to students in the undergraduates.

SmBCO 초전도 층착을 위한 RABiTS상의 CeO₂ 단일 버퍼 연구

김태형,김호섭,이남진,하홍수,고락길,하동우,송규정,오상수,박경채,Kim, Tae-Hyung,Kim, Ho-Sup,Lee, Nam-Jin,Ha, Hong-Soo,Ko, Rock-Kil,Ha, Dong-Woo,Song, Kyu-Jeong,Oh, Sang-Soo,Park, Kyung-Chae 한국전기전자재료학회 2007 전기전자재료학회논문지 Vol.20 No.6

As a rule, high temperature superconducting coated conductors have multi-layered buffers consisting of seed, diffusion barrier and cap layers. Multi-buffer layer deposition requires longer fabrication time. This is one of main reasons which increases fabrication cost. Thus, single buffer layer deposition seems to be important for practical coated conductor process. In this study, a single layered buffer deposition of $CeO_2$ for low cost coated conductors has been tried using thermal evaporation technique. 100 nm-thick $CeO_2$ layers deposited by thermal evaporation were found to act as a diffusion layer. $1\;{\mu}m-thick$ SmBCO superconducting layers were deposited by thermal co-evaporation on the $CeO_2$ buffered Ni-5%W substrate. Critical current of 90 A/cm was obtained for the SmBCO coated conductors.