• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.9
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• pp.801-804
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• 2000

High-temperature superconductor of Bi-2212 system was fabricated by CFP(Centrifugal Forming Process). To make a uniform specimen slurry was prepared in the ratio of 7:3(powder : binder) and ball milled for 24 hours. Milled slurry was charged into a rotating mold with 450 rpm and dried at room temperature. Then the specimen was performed binder burn-out at 35$0^{\circ}C$ and heated for partial melting to 86$0^{\circ}C$. XRD analysis of most specimens were shown 2212 phase and observed a local plate shped microstructure with a well aligned c-axis direction from SEM images. Measured T$_{c}$(Critical temperature) was about 64 K.K.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.189-192
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• 2000

High-temperature superconductor of Bi-2212 system was fabricated by CFP(centrifugal forming process). To make a uniform specimen slurry was prepared in the ratio of 7:3(powder:binder) and ball milled for 24 hours. Milled slurry was charged into a rotating mold with 450 rpm and dried at room temperature. Then the specimen was performed binder burn-out at 35$0^{\circ}C$ and heated for partial melting to 86$0^{\circ}C$. XRD analysis of most specimens were shown 2212 phase and observed a local plate shaped microstructure with a well aligned c-axis direction from SEM images. T$_{c}$(Critical temperature) of Bi-2212 was 64K.K.

• Proceedings of the SAREK Conference
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• 2006.06a
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• pp.613-618
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• 2006

The 1st International Conference on Magnetic Refrigeration at Room Temperature was held at Montreux, Switzerland during September 27-30, 2005. The conference was the first of its kind to bring together about 140 scientists and engineers interested in magnetic refrigeration in one place. The magnetocaloric effect was discovered in 1881, however, magnetic refrigeration at room temperature was demonstrated to be viable in 1997 Since then, R&D efforts toward magnetic refrigeration have been on the rise around the world, in both areas of systems and materials. The conference reflected the recent R&D trend in magnetic refrigeration at room temperature, which includes the use of permanent magnet instead of superconductor magnet, switch from reciprocating to rotary magnetic refrigeration system, development of magnetic materials based on transition metal elements besides rare earth materials such as gadolinium(Gd).

• Progress in Superconductivity and Cryogenics
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• v.26 no.2
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• pp.5-8
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• 2024

Recently, Lee et al. claimed that LK-99 isthe first room-temperature superconductor at ambient pressure, which quickly captured the attention of both the scientific community and the general public. We tried to replicate Pb_10-xCu_x(PO₄)₆O, called as LK-99, and characterized its physical properties by measuring the electrical resistance and Meissner effect. The electrical resistance results for different batches exhibited structural phase transitions at different temperatures, and the magnetic measurements indicated weak diamagnetism at 300 K, which is weaker than that of water. Taken together with the structural analysis, these results suggest that the resistivity transitions are incurred by Cu-S compound generated as a byproduct during the synthesis of LK-99 and LK-99 is not a room-temperature superconductor.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.229-232
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• 1999

We have measured the temperature dependence of thermoelectric power (TEP) and resistivity for the Sr$_{1-x}K_xBiO_3$ superconductor (x=0.45-0.6). At T=10.2K, the resisitivity starts to increase from zero and a rather broad superconducting phase transition (${\Delta}$T ${\sim}$ 2.3K) is observed. TEP at room temperature has a small negative value ( S =-1.96${\mu}$V/K), characteristic of metallic-like TEP. The temperature dependence of TEP shows two distinct features. With decreasing temperature from room temperature, the absolute value of TEP decreases and the sign of TEP changes from negative to positive around 200k. Also, the negative slope of TEP(dS/dT) decreases substantially and becomes rather flat at around 160k, which is a feature already noted in Ba$_{1-x}K_xBiO_3$[1].

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.628-631
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• 2001

Current lead is one of the first proposed devices for the application of High Temperature-Superconductor(HTSC). The current lead provides high current for electrical machine using superconductor from room temperature. Its characteristics that is zero resistance and low heat transfer rate under critical temperature lead to research for the replacement of existing current lead with HTSC. In this paper, we investigated the temperature distributions of stacking type and rod type current lead with each cross-section area and length using Nastran program and compared each temperature distribution. It is obtained from this paper that stacking type current lead has flat temperature gradient and than rod type one and more stable operation as current lead is closely related with its cross-section area and length.

• 한국초전도학회:학술대회논문집
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• v.9
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• pp.13-15
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• 1999

A Josephson sampler circuit using high-Tc superconductor (HTS) ramp-edge junctions has been designed, fabricated, and experimentally tested. It consists of five ramp-edge junctions with a stacked groundplane and is based on single-flux-quantum (SFQ) operations. The sampler was used to measure current waveforms at picosecond and microampere resolutions. We are developing a system based on the sampler for measuring the current waveform in a room-temperature sample. And measuring current flowing through wiring in a semiconductor large-scale integrated circuit is a promising application for the HTS sampler system.

• Progress in Superconductivity
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• v.1 no.2
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• pp.81-84
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• 2000

A Josephson sampler circuit using high-Tc superconductor (HTS) ramp-edge junctions has been designed, fabricated, and experimentally tested. It consists of five ramp-edge junctions with a stacked groundplane and is based on single-flux-quantum (SFQ) operations. The sampler was used to measure current waveforms at picosecond and microampere resolutions. We are developing a system based on the sampler for measuring the current waveform in a room-temperature sample. And measuring current flowing through wiring in a semiconductor large-scale integrated circuit is a promising application for the HTS sampler system.

• Journal of Magnetics
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• v.6 no.3
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• pp.83-85
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• 2001

The magnetoresistance properties of NiO/NiFe/Cu/NiFe spin valve film deposited on MgO(100) substrate with YBa$_2$$Cu_3O_7$(YBCO) film were investigated at room temperature and at 77 K. The magnetoresistance (MR) curves of the hybrid superconductor-magnetoresistor film structure showed an exchange coupling field of 300 Oe and an inverse magnetoresistance ratio of -6.5%. The magnetization configurations of the two magnetic layers in the NiO spin valve were antiparallel due to an increment in the conduction electron flow to superconductor YBCO film. This sample showed an inverse MR ratio.

• Progress in Superconductivity and Cryogenics
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• v.18 no.1
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• pp.33-36
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• 2016

Suppression of the superconducting transition temperature ($T_c$) of NbN thin films in superconductor/ferromagnet multilayers has been investigated. Both superconducting NbN and ferromagnetic FeN layers were deposited on thermally oxidized Si substrate at room temperature by using reactive magnetron sputtering in an $Ar-N_2$ gas mixture. The thickness of FeN films was fixed at 20 nm, while the thickness of NbN films was varied from 3 nm to 90 nm. $T_c$ suppression was clearly observed in NbN layers up to 70 nm thickness when NbN layer was in proximity with FeN layer. For a given thickness of NbN layer, the magnitude of $T_c$ suppression was increased in the order of Si/FeN/NbN, Si/NbN/FeN, and Si/FeN/NbN/FeN structure. This result can be used to design a spin switch whose operation is based on the proximity effect between superconducting and ferromagnetic layers.