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질산염 무기금속 화합물의 분무열분해법에 의한 High-$J_c$ YBCO 박막 제조
홍석관,김재근,김호진,조한우,유석구,안지현,주진호,이희균,홍계원,Hong, Suk-Kwan,Kim, Jae-Gun,Kim, Ho-Jin,Cho, Han-Woo,Yu, Seok-Koo,Ahn, Jin-Hyun,Joo, Jin-Hoo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
High $J_c$ over 1 $MA/cm^2$ YBCO film has been successfully prepared using nitrate precursors by spray pyrolysis method. Aerosol drolpets generated using a concentric spray nozzle were directly sprayed on a $LaAlO_3$(100) single crystal substrate. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:1.35. The distance between nozzle and substrate was 15 cm. Deposition temperature was ranging from $750^{\circ}C\;to\;800^{\circ}C$. Deposition pressure was 100 Torr, and oxygen partial pressure was varied from 10 Torr to 50 Torr. The microstructure, phase formation, texture development and superconducting properties of deposited films were largely changed with oxygen partial pressure. Deposited films showed a texture with(001) planes parallel to substrate plane. High quality film was obtained when film was deposited at $760^{\circ}C$ with an oxygen partial pressure of 30 Torr. The critical current density($J_c$) of the YBCO film was 1.75 $MA/cm^2$ at 77 K and self-field.
분사열분해 CVD 법으로 증착된 YBCO 박막의 특성에 미치는 기판 온도의 영향
김재근,홍석관,유석구,조한우,김병주,안지현,홍계원,이희균,Kim, Jae-Geun,Hong, Suk-Kwan,Yu, Seok-Koo,Cho, Han-Woo,Kim, Byung-Joo,Ahn, Ji-Hyun,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2007 Progress in superconductivity Vol.9 No.1
YBCO films have been synthesized using a spray pyrolysis method. We used nitrates of Y, Ba, Cu as precursors. Deposition was made on $LaAlO_3$ (100) single crystal substrate by spraying the mist of aqueous precursor solution generated by a concentric nozzle. The distance between concentric nozzle and substrate was 15 cm. C-axis oriented films were obtained at deposition temperature of $740{\sim}800^{\circ}C$ and working pressure of 20 Torr. Oxygen partial pressure was 3 Torr and substrate was transported with the speed ranging from 0.23 cm/min to 0.7 cm/min by reel to reel. Scanning electron microscope (SEM) and X-ray diffraction (XRD) observation revealed that films are smooth and highly textured with (001) planes parallel to substrate. Highest critical current density (Jc) was $1.38\;MA/cm^2$ at 77K and self-field for the film with a thickness of $0.5\;{\mu}m$ prepared at a substrate temperature of $780^{\circ}C$ and $PO_2\;=3\;Torr$. The effect of temperature on the microstructure and YBCO phase formation will be discussed.
기계적으로 분할된 YBCO 선재의 교류손실 감소에 대한 연구
유용수,홍계원,이희균,Yoo, Yong-Su,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도저온학회 2009 한국초전도저온공학회논문지 Vol.11 No.1
High temperature superconductor (HTS) coated conductors has high hysteretic magnetization loss which is an obstacle for the AC applications of coated conductors. We propose a method to reduce the magnetization loss of the coated conductor. It is the mechanical striation method by load variety using office knife. The magnetization loss measured in the mechanical striated YBCO coated conductor without copper layer was compared with the loss generated by perpendicularly exposed external magnetic filed. The reduction in magnetization loss due to the mechanical striation is clearly shown at higher field and was dependent on the striation number. The mechanical striation method was proven to have additional advantages of a low cost and high fabrication process.
Coated Conductor의 특성 및 미세조직에 미치는 고온열처리 영향
도민호,홍계원,이희균,Doh, Min-Ho,Hong, Gye-Won,Lee, Hee-Gyoun 한국초전도학회 2009 Progress in superconductivity Vol.11 No.1
고온초전도 CC를 다른 산소 분압에서 Ag과 YBCO의 녹는점 보다 낮은 온도에서 열처리시 CC의 특성에 미치는 영향을 실험하였다. 전류의 수송능력과 미세구조는 보호층인 Ag의 존재여부에 다양하게 영향을 미친다. Ag를 제거한 CC를 $850^{\circ}C$의 산소 분위기에서 2시간 동안 열처리 한 시편의 경우 CC의 임계전류의 특성에 영향을 미치지 않았다. 그러나 Ag를 제거하지 않은 CC를 $800^{\circ}C$의 산소 분위기에서 2시간 동안 열처리한 시편의 경우 임계전류가 140 A에서 8 A로 떨어지는 결과를 보였다. 또한, Ag을 제거하지 않은 CC를 1000 ppm 산소 분위기의 $800^{\circ}C$에서 2시간 동안 열처리한 시편의 경우 임계전류 값이 원래 $I_c$ 값의 $70{\sim}80%$의 임계전류 값이 나타났다. SEM 이미지와 XRD 회절 분석 결과 Ni과 Cr 원자들이 표면으로 확산되어 CC의 전류수송 특성에 영향을 미친다. HTS coated conductor was heat treated at high temperatures below the melting points of silver and YBCO at different oxygen partial pressures. Current carrying capacity and microstructure were varied depending on the presence of silver protection layer. Critical current of coated conductor without silver protection layer was not changed when heat treatment was performed at $850^{\circ}C$ for 2 hr in an oxygen atmosphere. However, coated conductor with silver protection layer revealed abrupt drop of $I_c$ from 140A to 8A when heat treatment was performed at $800^{\circ}C$ for 2 hr in an oxygen atmosphere. Coated conductor with silver protection layer retained $70{\sim}80$ percent of its original $I_c$ when heat treatment was performed at $800^{\circ}C$ for 2 hr in an argon atmosphere containing 1000ppm oxygen. SEM and XRD observations showed the presence of interaction between YBCO and silver depending on the atmosphere of heat treatment. The reaction between YBCO superconductor and silver was accelerated at high oxygen partial pressure and resulted in the change in microstructure and decrease of critical current density even by the heat treatment performed at temperature much lower than the melting points of silver and YBCO.
질산염 전구체 원료로 분무 열분해 방법에 의한 YBCO 박막 증착
김병주,홍석관,김재근,이종범,이희균,홍계원,Kim, Byeong-Joo,Hong, Seok-Kwan,Kim, Jae-Geun,Lee, Jong-Beom,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2010 Progress in superconductivity Vol.12 No.1
Y123 films have been deposited on $LaAlO_3$ (100) single-crystal and IBAD substrates by spray pyrolysis method using nitrate precursors. Ultrasonic atomization was adopted to decrease the droplet size, spraying angle and its moving velocity toward substrate for introducing the preheating tube furnace in appropriate location. A small preheating tube furnace was installed between spraying nozzle and substrate for fast drying and enhanced decomposition of precursors. C-axis oriented films were obtained on both LAO and IBAD substrates at deposition temperature of around $710{\sim}750^{\circ}C$ and working pressures of 10~15 torr. Thick c-axis epitaxial film with the thickness of $0.3{\sim}0.6\;{\mu}m$ was obtained on LAO single-crystal by 10 min deposition. But the XRD results of the film deposited on IBAD template at same deposition condition showed that the buffer layers of the IBAD metal substrate was affected by long residence of metal substrate at high temperature for YBCO deposition.
분무 열분해 CVD법으로 이동 중인 LaAlO_3(100) 단결정 위에 증착시킨 YBCO 박막의 특성
김재근,홍석관,김호진,유석구,조한우,안지현,주진호,이희균,홍계원,Kim, Jae-Gun,Hong, Suk-Kwan,Kim, Ho-Jin,Yu, Seok-Koo,Cho, Han-Woo,Ahn, Jin-Hyun,Joo, Jin-Hoo,Lee, Hee-Gyoun,Hong, Gye-Won 한국초전도학회 2006 Progress in superconductivity Vol.8 No.1
YBCO films were deposited on a moving substrate by a spray pyrolysis method using nitrate aqueous solution as precursors. Deposition was made on $LaAlO_3$(100) single crystal substrate by spraying precursor droplets generated by a concentric nozzle. The cation ratio of precursor solution was Y:Ba:Cu=1:2.65:4.5. The distance between nozzle and substrate was 15 cm. Substrate was transported with a speed ranging from 0.23 cm/min to 0.5 cm/min. Films were deposited at the pressure ranging from 10 Torr to 20 Torr and the deposition temperature was ranged from $740^{\circ}C\;to\;790^{\circ}C$. Oxygen partial pressure was controlled between 1 Tow and S Torr. Superconducting YBCO films were obtained from $740^{\circ}C\;to\;790^{\circ}C$ with an oxygen partial pressure of 3 Torr. Scanning electron microscope(SEM) and X-ray diffraction(XRD) observation revealed that films are smooth and highly texture with(001) plans parallel to substrate plane. Highest Jc was 0.72 $MA/cm^2$ at 77K and self-field for the film with a thickness of 0.15 m prepared at a substrate temperature of $740^{\circ}C$ and $PO_2$=3 Torr.
Fabrication of $YBa_{2}Cu_{3}O_{7-x}$-Ag Composite Superconductors by Pyrophoric Synthetic Method
양석우,김찬중,홍계원,신형식,Yang, Seok-U,Kim, Chan-Jung,Hong, Gye-Won,Sin, Hyeong-Sik Materials Research Society of Korea 1998 한국재료학회지 Vol.8 No.12
$YBa_2$$Cu_3$$O_{7-y}$ (123) 초전도체에서 은 입자의 미세분산을 얻고자 말릭산을 사용한 발화합성과 고상반응법으로 123와 123-Ag 복합 초전도분말을 제조하였다. 발화합성분말을 원료로 사용할 시 마이크론 미만의 미세한 123 분말과 은 분말의 복합체를 얻을 수 있었다. 원료로 사용된 산화은($Ag_2O$) 분말은 발화합성과정 중금속 은으로 환원되었다. 원료분말에 첨가된 금속 은에 의한 반응 물질간의 확산 촉진으로 123상이 단시간내에 생성되었고 입자성장도 촉진되었다. 발화합성법으로 제조한 시편은 기계적 혼합공정으로 제조한 시편에 비해 은 입자들은 미세하게 분산시킬 수 있어서 초전도체의 임계전류밀도가 향상되었다. To obtain fine dispersion of Ag particles in $YBa_2$$Cu_3$$O_{7-y}$ (123) superconductors, 123 samples were made by pyrophoric synthetic method using malic acid and the subsequent solid- state reaction. As the pyrophoric synthetic powder was used as a precursor material, fine 123 powder of submicron size was produced in a short reaction time. The added $Ag_2$O was converted to metallic Ag during Pyrophoric reaction and it accelerated both the formation of 123 phase and the grain growth via the enhanced mass transfer. The Ag particles of the sample sintered using the pyrephoric synthetic powder were more finely dispersed in the 123 matrix, compared to those of the sample sintered using the mechanically mixed powder, attributing to the improvement of the superconducting properties.
Deposition of Epitaxial YBCO Films on $LaAlO_3$(100) Substrate by Spray Pyrolysis Method
김호진,주진호,홍석관,이선왕,임선원,이희균,홍계원,Kim Ho-Jin,Joo Jinho,Hong Suk-Kwan,Lee Sun-Wang,Lim Sun-Weon,Lee Hee-Gyoun,Hong Gye-Won The Korean Superconductivity Society 2005 Progress in superconductivity Vol.7 No.1
[ $YBa_{2}Cu_{3}O_y$ ] superconducting films were prepared on $LaAlO_3$(100) single crystal substrate by spray pyrolysis method. The precursor solution was prepared by dissolving nitrate powders in de-ionized water. Both of ultrasonic and concentric nebulizers were used in order to generate fine droplets of precursor solution. C-axis oriented films were obtained at deposition temperature of $750\~850^{\circ}C$ and working pressure of 100 Torr and 500 Torr. In case of ultrasonic nebulizer, films showed rough and porous surface morphology due to formation of enormous droplets, while smooth and dense films were obtained for concentric nebulizer. A transport $J_c$ value of $0.43\;MA/cm^2$ at 77 K and self field was achieved on $LaAlO_3$(100) single crystal substrate.