• Proceedings of the Korean Nuclear Society Conference
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• 1998.10a
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• pp.267-267
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• 1998

• Progress in Superconductivity
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• v.13 no.3
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• pp.163-168
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• 2012

The effects of Ta substitution on the superconducting and magnetic properties of the $(Ru_{1-x}Ta_x)Sr_2(Gd_{1.4}Ce_{0.6})Cu_2O_z(0{\leq}x{\leq}0.5)$ system have been investigated. The X-ray diffraction measurements indicate that the Ta ion replaces Ru sites up to x = 0.4. It is found that the Ta substitution for Ru significantly reduces the weak-ferromagnetic component of the field-cooled magnetic susceptibility without an appreciable change of room temperature thermopower at lower Ta doping level below x = 0.2. The resistive transition temperature tends to decrease monotonically from 27 K for the x = 0 sample to 16 K (9 K) for the x = 0.4 (x = 0.5) sample. These results suggest that superconductivity of the $(Ru_{1-x}Ta_x)Sr_2(Gd_{1.4}Ce_{0.6})Cu_2O_z$ compound is not significantly affected by the magnetic state of the Ru sublattice. The experimental results are discussed in connection with previous reports on the effects of Nb substitution.

• Journal of the Korean Ceramic Society
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• v.42 no.5 s.276
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• pp.346-351
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• 2005

The linear thermal expansions of $UO_2$ and $(U_{1-y}Ce_y)O_2$ pellet were measured from room temperature to $1400^{\circ}C$ as a function of Ce contents (0, 7.63, 14.84, and $21.68 mol\%$) by using the TMA(Thermo-Mechanical Analysis) method. From the measured data, the linear thermal expansion rate, the coefficient of linear thermal expansion and density variation with temperature were calculated, and the best-fitted temperature-dependent equations were recommended. It was shown that the rate and coefficient of $(U_{1-y}Ce_y)O_2$ thermal expansion increased and the density decreased with increasing Ce contents.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.2
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• pp.152-157
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• 2001

For the fabrication of YBa$_2$Cu$_3$O$_{x}$ thick film using diffusion process between $Y_3$BaCuO$_{5}$ and BaO+CuO, each material was selected as substrate and doping material. In this paper, we investigated the characteristic of YBa$_2$Cu$_3$O$_{x}$ thick film due to both addition of CeO$_2$into substrate and initial particle size of doping material. Through X-ray diffraction patterns and SEM photographs, the variation of composition and thickness of the formed phase was observed. It was from the experiment obtained that the addition of CeO$_2$into $Y_2$BaCuO$_{5}$ substrate and the initial particle size of doping material play important part in promoting the reaction between substrate and doping material.aterial.

• Korean Journal of Metals and Materials
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• v.50 no.6
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• pp.439-443
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• 2012

YAG:Ce phosphor were prepared in a self-propagating high-temperature synthesis (SHS) using a $1.5Y_2O_3+2.5Al_2O_3+0.116CeO_2+3.0KClO_3+kCO(NH_2)_2+m(C_2F_4)_n$ precursor mixture. The heat for the combustion propagation was provided by the reaction of a $KClO_3+CO(NH_2)_2+(C_2F_4)n$ mixture. Pure-phase YAG phosphor was synthesized at the combustion temperature of $1210^{\circ}C$ from k=3.6 mole and m=0.3 mole. The as-prepared YAG:Ce phosphor had a particle size of $2-10{\mu}m$. The addition of Teflon to the precursor mixture increased the YAG particle size and its luminescent intensity. The emission peak of the YAG phosphor was blue-shifted with an increase of Teflon concentration.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2002.10b
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• pp.439-440
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• 2002

Nano-Crystalline $CeO_2$ particles were dispersed in deionized water with controlled slurry chemicals for CMP test. According to the CMP test, the removal rate of $SiO_2$ layer was mainly controlled by the size and crystallinity of $CeO_2$ particles which can be controlled by the heat-treatment condition during $CeO_2$ synthesis. In contrast, the removal rate of $Si_3N_4$ layer was significantly influenced by the passivation reagent which protects the $Si_3N_4$ surface layer from excessive dissolution during CMP.

• Progress in Superconductivity
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• v.10 no.2
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• pp.128-132
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• 2009

Polycrystalline samples of $(Ru_{0.8}Nb_{0.2})Sr_2(Gd_{1.5-x}Nd_xCe_{0.5})Cu_2O_z$($ 0{\leq}x{\leq}1.25$) have been synthesized by a solid-state reaction route. The X-ray diffraction data revealed that the Nd solubility limit can be placed between x=0.5 and x=0.75. The superconducting transition temperature decreased with increasing Nd content, confirming that Nd entered the lattice. Room-temperature thermoelectric power measurements showed that all the samples are in the underdoped state and the partial substitution of Nd for Gd resulted in a decrease in the carrier density on the superconducting layers.

• Current Applied Physics
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• v.18 no.12
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• pp.1465-1472
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• 2018

The magnetic and optical properties of Ce-doped ZnO systems have been widely demonstrated, but the effects of different strains of Ce-doped ZnO systems remain unclear. To solve these problems, this study identified the effects of biaxial strain on the electronic structure, absorption spectrum, and magnetic properties of Ce-doped ZnO systems by using a generalized gradient approximation + U (GGA + U) method with plane wave pseudopotential. Under unstrained conditions, the formation energy decreased, the system became stable, and the doping process became easy with the increase in the distances between two Ce atoms. The band gap of the systems with different strains became narrower than that of undoped ZnO without strain, and the absorption spectra showed a red shift. The band gap narrowed, and the red shift became weak with the increase of compressive strain. By contrast, the band gap widened, and the red shift became significant with the increase of tensile strain. The red shift was significant when the tensile strain was 3%. The systems with -1%, 0%, and 1% strains were ferromagnetic. For the first time, the magnetic moment of the system with -1% strain was found to be the largest, and the system showed the greatest beneficial value for diluted magnetic semiconductors. The systems with -3%, -2%, 2%, and 3% strains were non-magnetic, and they had no value for diluted magnetic semiconductors. The ferromagnetism of the system with -1% strain was mainly caused by the hybrid coupling of Ce-4f, Ce-5d, and O-2p orbits. This finding was consistent with Zener's Ruderman-Kittel-Kasuya-Yosida theory. The results can serve as a reference for the design and preparation of new diluted magnetic semiconductors and optical functional materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.29 no.2
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• pp.110-113
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• 2016

(YNdSm)-Ba-Cu-O system high Tc composite superconductors were directionally grown by zone melting process, having large temperature gradient, in air atmosphere. Cylindrical green rods of $(YNdSm)_{1.8}Ba_{2.4}Cu_{3.4}O_x$ [(YNS)1.8]composite oxides by CIP (cold isostatic pressing) method using rubber mold were fabricated. The microstructure and superconducting properties were investigated by XRD, TEM and SQUID magnetometer. The size of nonsuperconducting $(YNdSm)_2BaCuO_5$ inclusions of the melt-textured (YNS)1.8 sample with $CeO_2$ additive were remarkably reduced and uniformly distributed within the superconducting (YNS)1.8 matrix. (YNS)1.8 samples, with / without $CeO_2$ additive, showed an onset $T_c{\geq}90K$ and sharp superconducting transition. The critical current density $J_c$ value of the (YNdSm)1.8 superconductor with $CeO_2$ additive were 840 A, $1.2{\times}104A/cm^2$ in 77 K, 0 Tesla by direct current transport method.

• Journal of the Korean Ceramic Society
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• v.50 no.6
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• pp.485-488
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• 2013

A SiC-$CeO_2$ composite membrane was successfully fabricated using an ally-hydridopolycarbosilane (AHPCS) binder and treated by dip-coating at 60 times with a $CeO_2$ sol solution. The dip-coated SiC membrane was calcined at 773 K and then sintered at 1173 K under an air atmosphere. The coated membrane was characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM) and a BET surface analysis. The difference in permeation performance between $H_2$ and CO gases was measured by varying the temperature. The permeation flux of $H_2$ on the SiC membrane with layered $CeO_2$ was obtained as $8.45{\times}10^{-6}\;mol/m^2sPa$ at room temperature. The CO permeation flux was $2.64{\times}10^{-6}\;mol/m^2sPa$ at room temperature. The reaction enthalpy (${\Delta}H^{\circ}$) for the hydrogen permeation process was calculated as -7.82 J/mol by Arrhenius plots.