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白鉉德 홍익대학교 산업기술연구소 1998 産業技術 Vol.8 No.-
Electrical conduction of BaTh_0.9Y_0.1O_2.96 ceramics was investigated at 1276K. Total and partial conductivities were modeled using a method previously reported by the present author. The parameters used were derived based on the work of Tsuji and coworkers. Calculated conductivities showed a good agreement with the experimental results. The electrical conduction was dominated by holes in dry air and gradually dominated by protons with an increasing water pressure.
白鉉德 홍익대학교 산업기술연구소 1993 産業技術 Vol.2 No.-
The stability of Bi_2O_3 against reduction was investigated in the bismuth sesquioxide and alkaline earth oxide binary system. Using cells with alkaline earth fluoride as the solid electrolyte, the activity of CaO, SrO and BaO was measured. Then using Gibbs-Duhem integration, the activities of Bi_2O_3 were determined. In the high-ionic-conductive rhombohedral phase region, the activity of Bi_2O_3 decreased substantially in all three systems and showed negative deviation from Raoult's Law. The rhombohedral phase in the Bi_2O_3-SrO system showed the lowest activity of Bi_2O_3, 0.117 in the SrO-richest composition, (Bi_2O_3)_0.57(SrO)_0.43 at 630℃.
Ce_(1-x)Ca_(x)O_(2-δ) (x=1/6)에서의 프로톤 전도도
白鉉德 弘益大學校 産業技術硏究所 2004 産業技術 Vol.14 No.-
Electrical conductivity of sintered Ce_(1-x)Ca_(x)O_(2-δ) (x=1/6) was measured at temperatures 750, 800 and 850℃ in dry and wet air. No measurable conductivity increase was observed in wet atmosphere, as expected in usual proton-conducting oxides such as BaCeO₃, and thus it was concluded that no proton conduction occurs in this oxide due to the water absorption.
Y-도핑된 SrZrO_3 - 금속전극계의 전기전도 특성
白鉉德 홍익대학교 산업기술연구소 2001 産業技術 Vol.11 No.-
Electrical conduction in SrZr_xY_1-xO_3-δ(x= 0.05, 0.10)-metal electrode system was investigated by impedance spectroscopy and two-probe d.c. conductivity measurement. In 10%-doped samples, electrode conductivity in anodic direction varies with P_w^1/2 and that in cathodic direction with P_o2^1/4 in oxidizing atmosphere. In hydrogen atmosphere, the addition of water vapor increased the electrode conductivity both in anodic and cathodic direction. Increasing dopant concentration from 5 to 10% showed more than four times increase in anodic conduction as well as bulk conductivity of the solid electrolyte. This observation may be due the fact that the effective oxygen vacancy concentration is not proportional to the apparent dopant content. The activation energy of d.c. conductivity in Pt and Ag electrode was nearly same, which means the rate of cathodic reaction is determined by the reaction in the electrolyte surface rather than on the metal electrodes.
고온 프로톤전도체의 수소 분위기 하에서의 전기전도 특성
白鉉德 홍익대학교 산업기술연구소 2000 産業技術 Vol.10 No.-
Electronic conductivity was predicted for high-temperature proton-conductors based on their defect structure in the condition ionic defects are dominent over electronic ones. Electronic conductivity was expressed as a function of vapor pressures of oxygen and water vapor, not explicitly of hydrogen vapor pressure. Dissolution of water into the crystals of HTPCs bring about an increase in electronic conduction as well as proton conduction, and total conductivity was expected to show a rapid increase with an increasing water vapor pressure.
白鉉德 弘益大學校 産業技術硏究所 2007 産業技術 Vol.17 No.-
In the chemical diffusion of oxygen, given by ◁수식 삽입▷(원문을 참조하세요) the effect of the thermodynamic factors, Wc' and WVo' was studied. As the concentration of the charge carriers, oxygen vacancies or electrons, increases, the corresponding thermodynamic factor, Wv_(o') or Wv_(e'), is expected to decrease, and thus the contribution of the charge carrier whose concentration is larger than the other becomes smaller. In case the concentartion of electron increases, the effect of transport number being considered together in the given equation of ◁수식 삽입▷(원문을 참조하세요) above, the values of ◁수식 삽입▷(원문을 참조하세요) and ◁수식 삽입▷(원문을 참조하세요) reduce and that of ◁수식 삽입▷(원문을 참조하세요) become more significant. Analogously an enhanced concentration of oxygen vacancies will give rise to reductions of ◁수식 삽입▷(원문을 참조하세요) and ◁수식 삽입▷(원문을 참조하세요) and an increase in ◁수식 삽입▷(원문을 참조하세요). As a result, obviously it is shown that the chemical diffusion coefficient is controlled by the diffusion coefficient of charged species of a lower concentration.
白鉉德 홍익대학교 산업기술연구소 1994 産業技術 Vol.4 No.-
The free energy of formation of SrBi_2O_4 from its constituent oxides was determined at 630℃. The activity values of Bi_2O_3 and SrO were measured by the electrochemical e.m.f measurement method and free energy of formation was obtained to be -65.7kJ/mol by the relevant thermodynamic relation.
ABO₃형 페로브스카이트 산화물에서의 첨가산화물의 양이온의 크기에 따른 수증기 용해도 및 프로톤 전도도
白鉉德 홍익대학교 산업기술연구소 2006 産業技術 Vol.16 No.-
Doped cationic radius effect was studied on the water solubility and proton conductivity in doped ABO3-type perovskites. A similar ionic size of the doped rare earth ions with B cat ions gives a high water uptake and thus enhanced proton conduction.
고온프로톤전도성 산화물에 대한 수중기 분위기에서 σ tot vs. Po_2^1/4 그림으로 부터 전기전도도의 모델링
朴漢壽,白鉉德 홍익대학교 산업기술연구소 1997 産業技術 Vol.7 No.-
This work demonstrates a method for modeling of electrical conductivity in high-temperature proton-conduction oxides. Total conductivity was calculated assuming that it comprises partial conductivities contributed by proton. oxygen ion and electron hole. From the plot σ_tot vs po_2^1/4 in wet atmosphere, thermodynamic and kinetic parameters were obtained representing transport properties such as concentration and mobility of the charge-carrying defects. The formulae for the calculation of partial conductivities were derived based on the defect structure of HTPCs. Illustrative calculations were made for SrCe_0.95Yb_0.05O_2.976.
BaZr_0.95Y_0.05O_2.975의 전기전도 특성
朴漢壽,白鉉德 홍익대학교 산업기술연구소 1999 産業技術 Vol.9 No.-
Electrical conduction in BaZr_0.95Y_0.05O_2.975. was invesigated. Aging effect was observed in total conductivity. Partial conductivities, contributed, by protons, oxygen ions and electron holes, were determined from the relationship of total conductivity vs. partial pressures of water vapor and oxygen. Protons were minority defects, which had been observed in other zirconate HTPCs. As a result, proton conductivity and total conductivity increased with P_w^1/2