• Journal of the Korean Ceramic Society
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• v.39 no.4
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• pp.346-351
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• 2002

The electrical conductivity and phase stability of $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ were investigated in order to search for better solid electrolyte material for solid oxide fuel cell. Present study showed that $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ exhibited no phase transition during the heat treatment up to $1350^{Circ}C∼1550^{Circ}C$ and was stable as a cubic phase in whole temperature ranges. The $ZrO_2$ doped with $Sc_2O_3$ and $CeO_2$ showed much higher electrical conductivity than YSZ in the temperature range of $300∼^{Circ}C$ and better long term stability than other sc-$ZrO_2$ based electrolyte that showed the possibility as a strong candidate electrolyte material for intermediate-or low-temperature SOFC.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.6
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• pp.309-312
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• 2017

The ceria powder is excellent in oxygen storage capacity (OSC) through the oxidation and reduction reaction of Ce ions and is used as a typical material for a three-way catalyst of an automobile which purifies the exhaust gas. However, since ceria generally has poor thermal stability at high temperatures, it is doped with metal ions to improve thermal stability. Therefore, in this study, Zr ions were doped into ceria powder, and their characteristics were further improved due to the increase of specific surface area with decreasing particle size due to doping. In this study, the synthesis of zirconium doped ceria nanopowder was synthesized by hydrothermal process. In order to synthesis Zr ion doped ceria nanopowder, the precursor reaction at was $200^{\circ}C$ for 6 hours. The average particle size of synthesized Zr doped $CeO_2$ nanopowder was below 20 nm. The specific surface area of synthesized Zr ion doped ceria nanopowder increased from $52.03m^2/g$ to $132.27m^2/g$ with Zr increased 30 %.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.301-304
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• 2002

We investigated the structural and electrical properties of Ce-doped Ba($Zr_{0.2}Ti_{0.8}$)$O_3$(BCZT) thin films with a mole fraction of x=0.2 and a thickness about 100 nm. BCZT films were prepared on Pt/Ti/$SiO_2$/Si substrate by a RF magnetron sputtering system. We have measured the thickness profile with Ar/$O_2$ ratio and the surface roughness. It was observed that the oxygen gas, which introduced during the film deposition, have an influence on the roughness of the film and the film roughness was reduced by annealing from 2.33 nm to 2.02 m (RMS at $500^{\circ}C$, Ar:6 scrim, $O_2$:6 sccm). We have found that annealing procedure after top electrode deposit can reduce the dissipation factor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.361-364
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• 2003

It was investigated that the structural and electrical Properties of Ce-doped Ba(Zr$_{x}$Ti$_{1-x}$ )O$_3$ (BCZT) thin films with a mole fraction of x=0.2 and a thickness about 100 nm. BCZT films were prepared on Pt/Ti/SiO$_2$/Si substrate by a RF magnetron sputtering system. We have measured the thickness profile with Ar/O$_2$ ratio and the surface roughness. It was observed that the oxygen gas, which introduced during the film deposition, have an influence on the roughness of the film and the film roughness was reduced by annealing from 2.33 nm to 2.02 nm (RMS at 500 $^{\circ}C$, Ar:6 sccm, $O_2$:6 sccm). It was found that annealing procedure after top electrode deposit can reduce the dissipation factor.

• Applied Science and Convergence Technology
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• v.25 no.1
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• pp.19-24
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• 2016

In this study, we evaluated the change of electronic structure during redox process in cerium-doped $ZrO_2$ grown by sol gel method. By sol-gel method, we could obtain cerium-doped $ZrO_2$ in high oxygen partial pressure and low temperature. After post annealing process in nitrogen ambient, the film is deoxidized. We used spectroscopic and theoretical methods to analysis change of electronic structure. X-ray absorption spectroscopy (XAS) for O K1-edge and Density Functional Theory (DFT) calculation using VASP code were performed to verify the electronic structure of the film. Also, high resolution x-ray photoelectron spectroscopy (HRXPS) for Ce 3d was carried out to confirm chemical bond of cerium doped $ZrO_2$. Through the investigation of the electronic structure, we verified as followings. (1) During reduction process, binding energy of oxygen is increase. Simultaneously, oxidation state of cerium was change to 4+ to 3+. (2) Cerium 4+ and cerium 3+ states were generated at different energy level. (3) Absorption states in O K edge were mainly originated by Ce 4+ $f_0$ and Ce 3+, while occupied states in valance band were mainly originated from Ce 4+ $f_2$.

• The Korean Journal of Ceramics
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• v.5 no.1
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• pp.73-77
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• 1999

Capsule free hot isostatic pressing (HIPing) of 12 mol% $CeO_2-88 mo% ZrO_2 (12CeO_2-88ZrO_2)$ powder was conducted at 1100~$1200^{\circ}C$ using the powder crystallized in supercritical methanol followed by supercritical drying. Porous $12CeO_2-88ZrO_2$ ceramics with ~35% open porosity, micropore diameter of ~23 nm and a narrow pore size distribution were fabricated by capsule free hot isostatic pressing at $1100^{\circ}C$. The porosity increased with decrease in HIPing temperature and was accompanied by a steady decrease in fracture strength.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.1 no.1
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• pp.5-16
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• 1991

It was grown Cubic $ZrO_2(10 mol% Y_2O_3)$ single crystals doped with 1 wt% rare earth metal oxides (RE=Ce, Pr, Nd, Eu, Er) by Skull method. It was investigated electrical properties on (111) plane of grown single crystals by Impedance Spectroscopy. It was potted relation between temperature and electrical conductivities and observed the transition at $약300-400^{\circ}$ It was obtained activation energy on the migration of oxygen vacancy between low temperature (before the transition) and high temperature (after the transition till ${\11}500^{\circ}$) and its difference can be seen the activation energy of the formation of oxygen vacancies by break up defect complexes. It was obtained the activation energy according as add yttria and rare earth metal oxides and discussed ionic conduction mechanism. Grown single crystals showed Ce: orange - red, Pr: golden - yellow, Nd: lilac, Eu: light pink, Er: pink due to dopant effect from the light absorption data in the visible range.

• Nuclear Engineering and Technology
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• v.54 no.7
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• pp.2427-2434
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• 2022

Series of unequal quantity Nd/Ce co-doped ceramic nuclear waste forms, (Gd, Nd)₂(Zr, Ce)₂O₇, were prepared to tailor its ordered pyrochlore or disordered fluorite structure. The phase transition, microtopography, and elemental composition of the ceramic samples were systematically investigated, especially the effect of order-disorder structure on the chemical stability. It was confirmed that unequal quantity of Nd/Ce could synchronously replace the Gd/Zr-sites of Gd₂Zr₂O₇. And the phase transition of order-disorder structure could be successfully tailored by regulating the average cationic radius ratio of (Gd, Nd)₂(Zr, Ce)₂O₇ series. The elements of Gd, Nd, Zr, and Ce are uniformly distributed in the ordered or disordered structures. The MCC-1 leaching results showed that (Gd, Nd)₂(Zr, Ce)₂O₇ pyrochlore ceramic nuclear waste forms had excellent chemical stability, whose elements' normalized leaching rates were as low as 10^-4-10^-7 g·m^-2·d^-1 after 7 days. In particular, the chemical stability of disordered structure was superior to that of ordered structure. It was proposed that the force constant and the closest packing were changed with the structure transformation resulting the chemical stability difference.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.6
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• pp.311-317
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• 2009

3Y-TZP block doped with $HfO_2$ and $CeO_2$ for dental ceramic block to the proliferation of CAD/CAM systems was prepared by heating at $800{\sim}1100^{\circ}C$ and then sintering at $1450^{\circ}C$. The influences of heating temperature and addition of $HfO_2$ and $CeO_2$ on the mechanical and chemical properties of 3Y-TZP block were investigated. Using the EDS mapping images, $HfO_2$ and $CeO_2$ was well dispersed in the 3Y-TZP matrix. 3 wt% $HfO_2$ doped block showed the optimum biaxial strength (1 GPa), while 3 wt% $CeO_2$ doped block enhanced the stability of $t-ZrO_2$ under hydrothermal atmosphere.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.11a
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• pp.113-113
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• 2003

고체전해질체로 사용되는 산소이온전도체로는 $Y_2$O$_3$ 안정화 ZrO$_2$가 널리 연구되어 왔고, 실질적으로 많이 사용되고 있다. 그러나 특히 대전력을 얻고자 하는 고체전해질 연료전지 분야에 있어서는 다른 재료를 찾고자 하는 많은 노력이 이루어지고 있다. 이에 CeO$_2$계 세라믹스는 ZrO$_2$계보다 낮은 온도에서 더 높은 이온전도도를 가지고 있어 많은 주목을 받고 있다. 그러나 이 CeO$_2$계를 소결시키는 데는 1$600^{\circ}C$이상의 고온을 필요로 한다. 이 런 고온의 소결온도를 낮추기 위한 방안으로는 균일하고 미세한 출발원료를 사용하거나 소결조제를 첨가하는 것 등이 있다. 균일하고 미세한 출발원료를 제조하는 연구는 국내외에서 많이 이루어지고 있으나 소결조제 첨가에 대한 연구는 별로 이루어진게 없다. 다만 국외에서 Co$_3$O$_4$, Fe$_2$O$_3$, CoO 첨가에 의한 연구가 최근에 이루어지고 있으며, 본 연구실을 중심으로 Ga$_2$O$_3$, $Al_2$O$_3$ 첨가에 대한 연구가 이루어지고 있다. 본 연구실에서는 그간 공침법으로 제조되는 소결조제 첨가 Gd$_2$O$_3$-doped CeO$_2$ 분말을 사용하여 소결조제 첨가효과를 살펴보았다.