• Proceedings of the KIEE Conference
• /
• 2005.11a
• /
• pp.77-78
• /
• 2005

A high Tc superconducting with a nominal composition of $Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{Y}$ was prepared by the citarte method. The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. After pyrolysis at $400^{\circ}C$ and calcination at $840^{\circ}C$ for 4h, the (001)peak of the high Tc phase was cleary observed. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important factro in determining whether it is easy to form the high Tc phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1988.10a
• /
• pp.98-101
• /
• 1988

The material system (Bi$\sub$0.7/Pb$\sub$0.3/)Sr$_1$Ca$_1$Cu$\sub$1.8/Ox forms, at 845$^{\circ}C$, two major phases having a high Tc(100K) and a low Tc(∼70K) both of which consists of platelets and a non-superconducting minor phase which has rod-like shape and isolated by the major phases. As the sintering period increases, the amount of high Tc phase increases accompanying the decrease in low Tc phase while the amount of the non-superconducting phase is sintering period independent, resulting in a superconductor with Tc of 100K. Changes in compositions of each phase also occur during sintering due to evaporation of bismuth and lead.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.07a
• /
• pp.270-271
• /
• 2005

A high Tc superconducting with a nominal composition of $Bi_2Sr_2Ca_2Cu_3O_Y$ was prepared by the citarte method. The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. After pyrolysis at $400^{\circ}C$ and calcination at $840^{\circ}C$ for 4h, the (001)peak of the high Tc phase was cleary observed. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important factro in determining whether it is easy to form the high Tc phase or not. because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.153-154
• /
• 2005

A high Tc superconducting with a nominal composition of $Bi_2Sr_2Ca_2Cu_3O_Y$ was prepared by the citarte method. The solid precursor produced by the dehydration of the gel at 120$^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. After pyrolysis at 400$^{\circ}C$ and calcination at 840$^{\circ}C$ for 4h, the (001)peak of the high Tc phase was cleary observed. Experimental results suggest that the intermediate phase formed before the formation of the superconducting phase may be the most important factro in determining whether it is easy to form the high Tc phase or not, because the nucleation barriers of the two superconducting phase may be altered by the variation of the crystal structures of those intermediate phase.

• Journal of the Korean Ceramic Society
• /
• v.29 no.2
• /
• pp.95-100
• /
• 1992

A high-Tc superconducting phase was obtained using long sintering time of 210 hours. From XRD and SEM analyses, it could be confirmed that the particles were plate phase, of which the structure is tetragonal system with lattice parameter a=b=5.44${\AA}$, C=37.18${\AA}$. Resistance and current density measurements were carried out using 4 probe method. The experimental data revealed that the stable high-Tc superconducting phase was easily formed by addition of Pb to Bi-system. Therefore, we could find the sintering condition to synthesis the system having the largest fraction of high Tc phase.

• International Journal of Safety
• /
• v.7 no.2
• /
• pp.7-11
• /
• 2008

In this paper, a Magnetic Core Reactor (MCR) which forms a part of the DC reactor type three-phase high-Tc superconducting fault current limiter (SFCL) has been developed. This SFCL is more economical than other types with three coils since it uses only one high-Tc superconducting (HTS) coil. When DC reactor type three-phase high-Tc SFCL is developed using just one coil, fewer power electronic devices and shorter HTS wire are needed. The SFCL proposed in this paper needs a power-linking device to connect the SFCL to the power system. The design concept for this device was sprang from the fact that the magnetic energy could be changed into the electrical energy and vice versa. Ferromagnetic material is used as a path of magnetic flux. When high-Tc superconducting DC reactor is separated from the power system by using SCRs, this device also limits fault current until the circuit breaker is opened. The device mentioned above was named Magnetic Core Reactor (MCR). MCR was designed to minimize the voltage drop and total losses. Majority of the design parameters was tuned through experiments with the design prototype. In the experiment, the current density of winding conductor was found to be $1.3\;A/mm^2$, voltage drop across MCR was 20 V and total losses on normal state was 1.3 kW.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1990.10a
• /
• pp.26-30
• /
• 1990

Bi$\_$0.7/Pb$\_$0.3/Sr$_1$Ca$_1$Cu$\_$1.8/Ox thick films were screen printed on magnesia(MgO), silver and yttrium stabilized zirconia (YSZ) substrates and were sintered in a boat with cover to prevent the evaporation. The high-Tc phase increase and the low-Tc phase and Ca$_2$PbO$_4$ decrease with an increase in sintering temperature from 835$^{\circ}C$ to 860$^{\circ}C$. YSZ substrate interact strongly with the oxide resulting in poor superconductor, while the Ag and MgO substrates were satisfactory to make screen printed superconductors. The Bi$\_$0.7/Pb$\_$0.3/Sr$_1$Ca$_1$Cu$\_$1.8/Ox thick films screen printed both on Ag and MgO substrates show high Tc phase of ~85% and Tc of 96K.

• Proceedings of the KIEE Conference
• /
• 2006.07c
• /
• pp.1337-1338
• /
• 2006

BiSrCaCuO was prepared by the thermal pyrolysis method. The solid precursor produced by the dehydration of the gel at $120^{\circ}C$ for 12h is not in the amorphous state as expected but in a crystalline state. X-ray diffraction peaks of nearly the same angular position as the peaks of high Tc phase were observed in the precursor. After pyrolysis at $90^{\circ}C$ and calcination at $840^{\circ}C-920^{\circ}C$ for 4h, the high Tc phase was cleary observed. In this paper, the establishment of fabrication condition and additive effects of second elements were examined so as to improve the related properties to the practical use of BiSrCaCuO superconductor, and we reported the production of the BiSrCaCuO high Tc superconductor by the pyrolysis method.

• Korean Journal of Materials Research
• /
• v.1 no.2
• /
• pp.71-76
• /
• 1991

The superconducting powders in $YBa_2Cu_3O_{7-x}$ and Bi-Pb-Sr-Ca-Cu-O system were easily prepared from water in oil type emulsion by loading each cation into the aqueous phase. In $YBa_2Cu_3O_{7-x}$ system, the superconducting orthorhombic phase was formed by calcining at $750^{\circ}C$ for 10h in $O_2$. The size of the superconducting phase powders was submicron. The density of the sintered specimen using this powders was about 95% of the theoretical density and the resistance sharply decreases at about 90K, In Bi-Pb-Sr-Ca-Cu-O system the low Tc phase($(Bi, Pb)_2Sr_2Ca_1Cu_2O_y$) was formed by calcining at $800^{\circ}C$ for 10h in a low oxygen partial pressure of 1/20 atm The shape of clacined powder is thin plate of which size is about $2\mu\textrm{m}$ and thickness is smaller than $\mu\textrm{m}$. It was observed that the high Tc phase ($(Bi, Pb)_2Sr_2Ca_2Cu_3O_y$) was formed by sintering at $850^{\circ}C$ for 30h in oxygen pressure of 1/20 atm without intermediary grinding. The above sintered sample exhibited superconductivity with a Tc(zero)=105K.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.5C no.5
• /
• pp.217-220
• /
• 2005

We have fabricated a superconducting YBCO system according to the pyrolysis method and low pressure apparatus. In our experiment, the X-ray diffraction pattern of the non doped YBaCuO layer indicated that the superconductor contained only 90K phase crystal. The critical temperature and critical current density for a thick layer at $650^{\circ}C$ were Tc=90 K and $Jc=6{\times}10^{4}A/cm^2$ at 90K. In low pressure apparatus, the 90 K phase YBaCuO was grown at a lower temperature compared with the normal system. Tc and Jc at $650^{\circ}C$ were Tc = 90 K and $Jc=6{\times}10^{4}A/cm^2$ at 90K.