• Electrical & Electronic Materials
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• v.7 no.4
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• pp.281-288
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• 1994

According to spread volume of B(BiPbCuO) layer, composition ratio and each stage of sintering process, we studied stability of high Tc superconductor phase and generation and growth movement of superconducting phase. The dual layer composed of SrCaCuO and BiPbCuO compound were prepared to develop the Bi-2223 superconductor[108K] through interaction and diffusion during sintering process. The dual layer samples were sintered at 830.deg. C for 0-210 hours. From the result, the optimum conditions were : spread volume(A:B=1:0.6), sintering time(210h) and composition ratio(A:S $r_{2}$C $a_{2}$C $u_{2}$- $O_{x}$, B:B $i_{1.9}$P $b_{0.5}$C $u_{3}$ $O_{y}$) at 830.deg. C.. C.C.C.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 1999.02a
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• pp.3-9
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• 1999

The grain morphology, the changes in morphology and Jc with the thermo-mechanical treatment (TMT) history, the field dependence of Jc and the nature of intergranular bonding were studied in $T_{10.8}$$Pb_{.2}$$Bi_{0.2}$$Sr_{1.8}$$Ba_{0.2}$$Ca_{2.2}$$Cu_{3}$$O_{z}$/Ag tapes. As a result, incorporation of intermediate rolling during the final heat-treatment resulted in of plate-like TI-1223 grains, and thus enhanced Jc. Jc's near 2.5$\times$104 A/cm2 at 77 K and 0 T were obtained in just rolled tapes with an excellent reproducibility. The high Jc's seem to grain-connectivity easy recovery of excellent grain-connectivity during final heat-treatment after inter -mediate rolling, probably due to retarded T1 evaporation and excessive Ca content in the present composition. The strong field dependence of Jc even in low fields, however, indicated that there still existed significant weak-links and the degree of directional grain-alignment was far from the desired one. The intergranular binding in the tapes seemed to be mainly dominated by SIS junctions.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.252-254
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• 2003

A magnetic field sensor is fabricated with superconducting ceramics system. The sensor at liquid nitrogen temperature shows the increase in electrical resistance by applying magnetic field. Actually, the voltage drop across the sensor is changed from zero to a value more than $100{\mu}V$ by the applied magnetic field. The change in electrical resistance depends on magnetic field. The sensitivity of this sensor is 2.9 ohm/T. The increase in electrical resistance by the magnetic field is ascribed to a modification of the Josephson junctions due to the penetrating magnetic flux into the superconducting material.

• Journal of the Korean Ceramic Society
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• v.40 no.5
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• pp.405-409
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• 2003

The effect of substitution of Gd ions for Ca ions in the B $i_{1.84}$P $b_{0.34}$S $r_{1.91}$(C $a_{1-x}$ G $d_{x}$)$_{2.03}$ C $u_{3.06}$ $O_{ 10+{\delta}}$/ (x=0.0~0.06) was investigated by measuring x-ray diffraction patterns, lattice constants, do resistivity and Hall effect. We found the solubility limit of Gd in the 110 K phase to be x < 0.015. Within the solubility limit, the c-axis seemed to decrease with increasing x. In the region of the 110 K single phase, the critical temperature $T_{c}$ gradually decreased with an increasing the Gd concentration x, corresponding to a small change of the carrier concentration.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2000.02a
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• pp.6-8
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• 2000

The critical current density, Jc, of superconductor tape significantly depends on microstructural evolution during mechanical deformation. In this study, we fabricated Bi-2223 superconductor tape by PIT technique, and investigated mechanical properties of mono- and 61-filamentary tapes and their joined tapes. The strength of mono-filament tape was higher than those of 61-filament tape was higher than those of 61-filament tape, respectively. On the other hand, elongation of mono-filament tape, respectively. On the other hand, elongation of mono-filament tape was lower than 61 filament tape. The joined tapes shows lower strength and irreversible strain than those of unjoined tapes. The reduced strength and irreversible strain for joined tape is probably related to the induced damages such as irregular interface and Ag-instrusion in the transition region which acts as a stress concentration.

• Proceedings of the KIEE Conference
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• 1998.07a
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• pp.349-352
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• 1998

In future superconducting electrical machines and device. AC loss in the superconducting windings are one of the most impotent design paramenters. This paper descriptions a series of Characteristic of a high-Tc superconducting Bi-Pb-Sr-Ca-Cu-O Ag-sheathed filament. In the case simulation and design to reduce ac loss is considered the filament number, twitch pith number and diameter of filament. A filament sample with Tc of 78K is made by $835^{\circ}C$ sintering for 50h and $0.33^{\circ}C$/min heating rate in an atmosphere. The experiment observations are compared with self-field loss and AC losses of Bi-Pb-Sr-Ca-Cu-O filament at 77K in following environments ; (i)AC external parallel magnetic field in different frequencies. And an analytical expression of the loss the derivation of transposition from an optimum condition was derived for the external AC magnetic field, theoretical predictions were found to coincide with the experimental observations.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.268-279
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• 1994

The x-ray powtler pattern of single phase $Bi_2S_2CaCu_2O_{8+x}$ has been identified and fullyindexed using a pseudotetragonal subcell with a= 5.408, c = 30.83 $\AA$ and an incommensurate supercellwith reciprocal lattice vector, X$q^*$, given by $q^*=0.211b^*-c^*$. The x -ray powder pattern of the Pb-free110K superconductor phase "$Bi_2S_2CaCu_2O_{10+x}$" has many lines which belong t.o an incommensuratesupercell. Using elect.ron d~ffraction pImt.ographs as a indexing guide, an indexing scheme for the powderpattern has been obtained. The unit cell has a geometrically orthorhombic subcell a=5.411, b= 5.420, c=37.29(2) $\AA$. Supercell reflections have indices that are derived from the subcell k, 1 indices by addition uf$\pm q^*$, where $\pm q^*=0.211b^*-0.78c^*$The incommensurate con~ponent In the b dwection, $\delta$, is the same for both phases but on going from2212 to 2223 phase, the superlattic component in the c direction changes from commensurate($\varepsilon$=1) toincommensurate($\varepsilon$=0.78).X>$\varepsilon$=0.78).

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.116.2-116.2
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.221-223
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• 1999

In this work, samples were manufactured variously by changing conventional calcining and sintering conditions and we tried the utilization by making the heat treatment time, which is demanded to high-Tc phase formation, much shorter. We found out optimal heat treatment conditions with the analysis on formation process at superconducting phase in term of the change of calcining and sintering time and then, examined X-ray diffraction(XRD) patterns, scanning electron microscope(SEM) measurement and energy dispersive X-ray spectrometer(EDX) of the samples manufactured under heat treatment conditions which we suggest here. As a result, 2223 high-$T_c$, phase of (Bi,Pb)SrCaCuO superconductor starting with ($Bi_l$ xPbx,)$_2$$Sr_2$$Ca_2$$Cu_3$$O_y$, composition was formed from 1 hr sintering sample at temperature nearby melting point and also the completed sample with calcining and sintering time of 9 hr was formed high-$T_c$.low-$T_c$ phase appearing in sight above the critical temperature of liquid $N_2$.

• Progress in Superconductivity and Cryogenics
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• v.21 no.4
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• pp.1-5
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• 2019

We investigated the effect of Fe₃O₄ addition on the critical temperature of (Bi, Pb)-2223 polycrystalline samples. Bi_1.6Pb_0.4Sr₂Ca₂Cu₃O_10+δ + x wt. % Fe₃O₄ (x = 0.0, 0.2, 0.4, 0.6, and 0.8) samples were prepared by using a solid-state reaction method. The analysis of X-ray diffraction data indicates that as Fe₃O₄ is added, dominant phase of the sample changes from Bi-2223 to Bi-2212 with an increasing Bi-2201 phase. The transition temperature of the samples drastically decreased with the Fe₃O₄ addition. The resistance data of samples with x = 0.2 and 0.4 showed a double transition indicating a coexistence of Bi-2223 and Bi-2212 phase while the samples with x = 0.6 and 0.8 showed a single transition with a semiconducting behavior. This phase transition may originate from changes in local structure of the Bi-2223 system by Fe₃O₄ addition. Analysis of the pair distribution function of the Cu-O pair in the CuO₂ plane calculated from extended X-ray absorption fine structure data revealed that the oxygen coordination of copper ion changes from CuO₄ planar type (x = 0.0 - 0.4) to CuO₅ pyramidal type (x = 0.6, 0.8). The correlated Debye-Waller factor, providing information on the atomic disorder within the CuO₂ plane, shows an inverse relation to the coordination number. These results indicate that addition of Fe₃O₄ changes the oxygen distribution around Cu in the CuO₂ plane, causing a phase transition from Bi-2223 to more stable Bi-2212/Bi-2201 phases.