• Current Applied Physics
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• v.18 no.12
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• pp.1513-1522
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• 2018

Bismuth telluride ($Bi_2Te_3$) thin films were prepared with various electrolyte temperatures ($10^{\circ}C-70^{\circ}C$) and concentrations [$Bi(NO_3)_3$ and $TeO_2:1.25-5.0mM$] in this study. The surface morphologies differed significantly between the experiments in which these two electrodeposition conditions were separately adjusted even though the applied current density was in the same range in both cases. At higher electrolyte temperatures, a dendrite crystal structure appeared on the film surface. However, the surface morphology did not change significantly as the electrolyte concentration increased. The dendrite crystal structure formation in the former case may have been caused by the diffusion lengths of the ions increasing with increasing electrolyte temperature. In such a state, the reactive points primarily occur at the tops of spiked areas, leading to dendrite crystal structure formation. In addition, the in-plane thermoelectric properties of $Bi_2Te_3$ thin films were measured at approximately 300 K. The power factor decreased drastically as the electrolyte temperature increased because of the decrease in electrical conductivity due to the dendrite crystal structure. However, the power factor did not strongly depend on the electrolyte concentration. The highest power factor [$1.08{\mu}W/(cm{\cdot}K^2$)] was obtained at 3.75 mM. Therefore, to produce electrodeposited $Bi_2Te_3$ films with improved thermoelectric performances and relatively high deposition rates, the electrolyte temperature should be relatively low ($30^{\circ}C$) and the electrolyte concentration should be set at 3.75 mM.

• Journal of Sensor Science and Technology
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• v.23 no.3
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• pp.170-172
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• 2014

$CO_2$ sensor was used only one solid electrolyte in many cases. To improve the sensing characteristics of $CO_2$ sensors, solid electrolyte $CO_2$ sensor has been developed by bi-electrolyte type sensor using Na-Beta-alumina and YSZ. However, in many further studies, bi-electrolyte type sensor was made by pellet pressed by press machine and additional treatment for formation of interface. In the aspect of mass production, using thick film and additional treatment is not suitable. In this study, $CO_2$ sensor was fabricated by bi-electrolyte structure which was made by an NBA paste layer deposited on YSZ pellet and fired at $1650^{\circ}C$ for 2 hour. The formation of stable interface between YSZ and NBA were confirmed by SEM image. When the type IV electrochemical cell arrangement represented by $CO_2,O_2,Pt{\mid}Li_2CO_3-CaCO_3{\parallel}NBA{\parallel}YSZ{\mid}O_2,Pt$ is used to measure the $CO_2$ concentration in air. This sensor EMF should depend only on the concentration of $CO_2$ by logarithmic. Also, sensor shows $P_{CO_2}$ and EMF relationship like nerstian reaction at a temperature of $450^{\circ}C$.

• Journal of the Korean Ceramic Society
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• v.32 no.2
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• pp.248-256
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• 1995

The electrical conducton in the sintered 3Bi2O3.WO3 solid electrolyte was investigated by measuring the conductivity and ionic transport number. The electrical conductivity was about three to ten times higher than that of YSZ at temperatures between 300 and 80$0^{\circ}C$. D.C. polarization method confirmed that 3Bi2O3.WO3 was predominantly an ionic conductor. Unlike the instability of high conductive fcc phase in the rare-earth oxide-Bi2O3 or Y2O3-Bi2O3 systems at temperature below $700^{\circ}C$, fcc phase in the 3Bi2O3.WO3 exhibited no transformation even after annealing over 900 hrs at 600 and $650^{\circ}C$. Two samples which had different grain sizes showed almost the same conductivity. This result suggests that the electrical properties of grain and grain boundry were very similar.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1003-1004
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• 2011

• Bulletin of the Korean Chemical Society
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• v.33 no.5
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• pp.1541-1546
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• 2012

The early stages of bismuth (Bi) electrodeposition on glass carbon electrode from alkaline electrolyte were studied by cyclic voltammetry, chronoamperometry, scanning electron microscopy, atomic force microscopy and X-ray diffraction. The CV analysis showed that the electrodeposition of Bi was determined to be quasireversible process with diffusion controlled. The current transients for Bi electrodeposition were analyzed according to the Scharifker-Hills model and the Heerman-Tarallo model. It can be concluded that the nucleation and growth mechanism was carried out under a 3D instantaneous nucleation, which was confirmed by SEM analysis. The kinetic growth parameters were obtained through a nonlinear fitting. In addition, the Bi film obtaining at -0.86 V for 1 hour was of compact and uniform surface with good smoothness, small roughness and a very high purity. The Bi film were indexed to rhombohedral crystal structure with preferred orientation of (0 1 2) planes to growth.

• Journal of the Korean Ceramic Society
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• v.42 no.12 s.283
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• pp.808-815
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• 2005

[ $Bi_xCe_{l-x}O_{2-x/2}$ ](BD C : Bismuth Doped Ceria) powders with x = 0.1, 0.2, and 0.3 were synthesized using the Glycine Nitrate Process (GNP). They were then calcined at $500^{\circ}C$ for 2 hand sintered in a pellet or rod form at 900, 1000 or $1100^{\circ}C$ for 4 h for characterization as the alternative electrolyte material for intermediate temperature solid oxide fuel cells. The BDC powder consisted of a single phase of $CeO_2-Bi_2O_3$ solid solution in the as-synthesized state as well as in the as-calcined state with a mean powder size of 4.5nm in the former state and 6.5 - 10.1nm in the latter. On the contrary, the second phase of $\alpha-Bi_2O_3$ was observed to have been formed in the sinter with its amount increasing roughly with increasing temperature or $Bi_2O_3$ content. The BOC powder was superior in sinterability to other alternative electrolyte materials such as GDC, ScSZ, and LSGM with the minimum sintering temperature for a relative density of $95\%$ or larger as low as $1100^{\circ}C$. The ionic conductivity of BOC increased with $Bi_2O_3$ content and the maximum value of 0.119 S/cm was obtained at $800^{\circ}C$ for $Bi_{0.3}Ce_{0.7}O_{1.85}$.

• Proceedings of the Materials Research Society of Korea Conference
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• 1993.11a
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• pp.126-126
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• 1993

• Journal of the Korean Ceramic Society
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• v.51 no.4
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• pp.289-294
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• 2014

The stability of a solid oxide fuel cell (SOFC) stack is strongly dependent on the magnitude and profile of the internal chemical potential of the solid electrolyte. If the internal partial pressure is too high, the electrolyte can be delaminated from the electrodes. The formation of high internal pressure is attributed to a negative cell voltage, and this phenomenon can occur in a bad cell (with higher resistance) in a stack. This fact implies that the internal chemical potential plays an important role in determining the lifetime of a stack. In the present work, we fabricate planar type anode-supported cells ($25cm^2$) with a bi-layer electrolyte (with locally increased electronic conduction at the anode side) to prevent high internal pressure, and we test the fabricated cells under a negative voltage condition. The results indicate that the addition of electronic conduction in the electrolyte can effectively depress internal pressure and improve the cell stability.

• Journal of Energy Engineering
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• v.20 no.2
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• pp.77-83
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• 2011

It is requested to improve negative electrode of Ni-Zn battery for industrial application. Ni-Zn battery has main problems not to commercialize because of short life cycle, heavy gassing and fast electrolyte vaporization so far. It has been studied on 8 cells performances under promoting electric, additional materials and binders changed. With these materials($Ca(OH)_2$, $Bi_2O_3$), negative electrolyte can be manufactured equal and tight as well as low gassing. Furthermore, to supply EG-EP#12(gravity 1.26), keeping stable electrolyte gravity in battery, the life cycle of Ni-Zn battery is extremely improved 200~300% than initial performance.

• 한국전기화학회:학술대회논문집
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• 1999.11a
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• pp.83-91
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• 1999

Technical advances in manufacturing techniques and applied technologies have been made for bi cell manufacture, and are currently being implemented in the areas of discrete electrode / bi cell assembly, and electrode / separator lamination. Not only have improvements been noted in the reliability of the mechanical assembly and the increase in yields and decrease in costs, battery electrical performance has also been enhanced thru these assembly techniques. Evidence has been shown that the lamination techniques can influence porosity and electrolyte dispersion, and therefore electrical performance and long term reliability of the cells.