• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.258-262
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• 2016

The effect of zirconium dioxide ($ZrO_2$) on the properties of color conversion glasses was examined in the $BaO-ZnO-B_2O_3-SiO_2$ system. The difference in refractive index between glass and phosphor affect the optical properties of the color conversion glass because of light scattering. Reducing the difference in refractive index is a method to improve the luminous efficacy of color conversion glasses. As a reference, a type of glass that contains 25 mol% of each component was used. To increase the refractive index of the glass samples, the BaO content was increased from 25 to 40 mol%, and $ZrO_2$ was added at levels of 1, 3, and 5 mol%. Color conversion glasses were prepared by sintering a mixture of glass and 5 wt% $YAG:Ce^{3+}$ phosphor. As a result, the refractive index of the glass was found to be dependent on the BaO and $ZrO_2$ contents in the BaO-ZnO-$B_2O_3-SiO_2$ system. As the BaO and $ZrO_2$ contents were increased, the luminous efficacy of the color conversion glass was improved because the refractive index difference between the glass and the $YAG:Ce^{3+}$ phosphor decreased.

• Journal of Sensor Science and Technology
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• v.17 no.2
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• pp.127-132
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• 2008

The effect of $CeO_2$ as a sintering additive on the microstructure and the piezoelectric property of yPb$(Sb_{0.5}Nb_{0.5})O_3$-(1-y)Pb$(Zr_{0.52}Ti_{0.48})O_3$ ($0{\leq}y{\leq}0.1$, PSN-PZT) for a hypersonic sound speaker (HSS) application was investigated. The samples were sintered at $1250^{\circ}C$ for 2 h. The crystal structure and surface morphology of the samples were examined using XRD and FE-SEM, respectively. Study on the influence of $CeO_2$ additives on the dielectric and piezoelectric properties indicated that the $CeO_2$-added PSN-PZT system had a high piezoelectric properties. The optimized results of ${\varepsilon}_r=1209$, $K_p$=52% $d_{33}$=351(pC/N) and $Q_m$=1230.16 were obtained at 0.4 wt.% $CeO_2$-added PSN-PZT.

• Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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• 2003.02a
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• pp.129-132
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• 2003

Yttria stabilized zirconia (YSZ) buffer layers were deposited by a metal organic chemical vapor deposition (MOCVD) technique using single liquid source for the application of YBa$_2$Cu$_3$$O_{7-x}$ (YBCO) coated conductor. Y:Zr mole ratio was 0.2:0.8, and tetrahydrofuran (THF) was used as a solvent. The (100) single crystal MgO substrate was used for searching deposition condition. Bi-axially oriented CeO$_2$ and NiO films were fabricated on {100}〈001〉 Ni substrate by the same method and used as templates. At a constant working pressure of 10 Torr, the deposition temperatures (660~80$0^{\circ}C$) and oxygen flow rates (100~500 sccm) were changed to find the optimum deposition condition. The best (100) oriented YSZ film on MgO was obtained at 74$0^{\circ}C$ and $O_2$ flow rate of 300 sccm. For YSZ buffer layer with this deposition condition on CeO$_2$/Ni template, full width half maximum (FWHM) values of the in-plane and out-of-plane alignments were 10.6$^{\circ}$ and 9.8$^{\circ}$, respectively. The SEM image of YSZ film on CeO$_2$/Ni showed surface morphologies without microcrack.k.

• Journal of the Korean Ceramic Society
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• v.56 no.1
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• pp.91-97
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• 2019

The effect of different Ni-containing additives on the sintering behavior and electric conductivity of the proton conducting electrolyte $BaCe_{0.35}Zr_{0.5}Y_{0.15}O_{3-{\delta}}$ (BCZY5) was investigated. Ni-doped, NiO-added, and $BaY_2NiO_5$(BYN)-added (all 4 mol%) BCZY5 samples were prepared by the solid state synthesis method and sintered at $1400^{\circ}C$ for 6 h. Among the three samples, the onset of densification was observed at the lowest temperature for NiO-added BCZY5, which is attributed to the formation of an intermediate phase at a low melting temperature. The BYN-added sample, where no consumption of the constitutional elements of the electrolyte was expected during sintering, exhibited the highest electrical conductivity whereas the doped sample had the lowest conductivity. The electrical conductivities at $500^{\circ}C$ under humid argon atmosphere were measured to be 2.0, 4.8, and $6.2mS{\cdot}cm^{-1}$ for Ni-doped and NiO- and BYN-added samples, respectively.

• The Korean Journal of Ceramics
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• v.4 no.2
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• pp.146-150
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• 1998

The total conductivity and oxygen permeation in (Ce1-xZrxO2)0.9(CaO)0.1 solid solutions were measure das a function of temperature and oxygen partial pressure. Empirically, σ at given x and T was expressed essentially by σ=σo2+σeo Po2-1/4, where σo2 and σeo are constant. Applying a standard defect model in which major defects are Cace", Cece' and Vo in ideal solution, we can assign σo2 as the oxide ion conductivity decreases while the electronic conductivity increases with the increase in Zr content. Using the oxide ion and electronic conductivities thus determined, the oxygen permeation flux was calculated for respective Po2 and T conditions at which the measurements were made. The calculated values were found to agree with the observed ones.

• Proceedings of the Materials Research Society of Korea Conference
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• 2008.11a
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• pp.35.2-35.2
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• 2008

• Economic and Environmental Geology
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• v.30 no.1
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• pp.1-14
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• 1997

The shales from the Euiseong area are interbedded along the bedding in Cretaceous Gyeongsang Supergroup, which are composed mainly of quartz, plagioclase, K-feldspar and associated with trace amount of biotite, muscovite, chlorite, pyrite, hematite, carbonate and clay minerals. The ratio of $Al_2O_3/Na_2O$ and $K_2O/Na_2O$ in shales from the Shindong Group are ranged from 9.16 to 24.32 and from 1.70 to 5.97, and the Hayang Group ranged from 2.76 to 8.89 and from 0.42 to 2.74, which are negative correlated between $K_2O/Na_2O$ and $Al_2O_3/Na_2O$ against $SiO_2/Al_2O_3$ respectively. Those are suggested that controlled of mineral compositions in shales due to substitution and migration of elements by sedimentation and diagenesis. These shale formation were deposited in basin of terrestrial environments originated from the igneous rocks, and the REE of these rocks are not influenced with diagenesis and hydrothermal alterations on the basis of $Al_2O_3$ versus La, La against Ce, Zr versus Yb, the ratios of La/Ce (0.43 to 0.62) and Th/U (1.11 to 10.71). The narrow range in trace and REE element characteristics as Co/Th (0.63 to 1.92), La/Sc (1.98 to 5.90), Sc/Th (0.58 to 1.30), V/Ni (0.90 to 3.25), Cr/V (0.45 to 1.78), Ni/Co (1.88 to 6.67) and Zr/Hf (30.04~60.87) of these shales argues for inefficient mixing of the simple source lithologies during sedimentation. These rocks also show much variation in $La_N/Yb_N$ (6.90 to 17.02), Th/Yb (4.17 to 13.68) and La/Th (1.98 to 5.90), and their origin is explained by derivation from a mixture of intermediate to acidic igneous rocks.

• Journal of Korea Foundry Society
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• v.39 no.2
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• pp.21-25
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• 2019

Microstructural and corresponding hardness changes of TiFe compounds with Zr (0~6 at%) or Ce (0~3 at%) were studied using samples prepared at different solidification rates. In arc-melted (TiFe)-Zr samples, the $Fe_{23}$ $Zr_6$ and $(Ti,\;Zr)_2Fe$ phases formed in the TiFe matrix, while in the (TiFe)-Ce sample, the $CeO_2$ phase formed along the grain boundary of the TiFe matrix. As the Zr content was increased, the volume fractions of the $Fe_{23}$ $Zr_6$ and $(Ti,\;Zr)_2Fe$ phases increased, forming a network structure. Accordingly, the hardness values of the samples also increased. With a small addition of Ce of approximately 0.1 at%, the as-cast microstructure could be effectively refined, reducing the average grain boundary diameter from ${\sim}100{\mu}m$ to ${\sim}14{\mu}m$. In the rapidly solidified sample prepared through a melt-spinning method, the constituent phases were identical to those of the arc-melted samples while the grains were refined. The microstructural changes of TiFe alloys can affect the hydrogen storage ability as well as the mobility of the hydrogen atoms in the alloys.

• Journal of the Korean Solar Energy Society
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• v.37 no.5
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• pp.27-37
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• 2017

In this study, an artificial solar simulator composed of a 2.5 kW Xe-Arc lamp and mirror reflector was used to carry out the solar thermal two step thermochemical water decomposition cycle which can produce high efficiency continuous hydrogen production. Through various operating conditions, the change of hydrogen production due to the possibility of a dual-zone reactor and heat recovery were experimentally analyzed. Based on the reaction temperature of Thermal-Reduction step and Water-Decomposition step at $1,400^{\circ}C$ and $1,000^{\circ}C$ respectively, the hydrogen production decreased by 23.2% under the power off condition, and as a result of experiments using heat recovery technology, the hydrogen production increased by 33.8%. Therefore, when a thermochemical two-step water decomposition cycle is conducted using a dual-zone reactor with heat recovery, it is expected that the cycle can be operated twice over a certain period of time and the hydrogen production amount is increased by at least 53.5% compared to a single reactor.

• Journal of the Korean Ceramic Society
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• v.54 no.5
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• pp.422-428
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• 2017

Single-phase yellow phosphor, $CaGd_{2-x}ZrSc(AlO_4)_3:xCe^{3+}$ ($CGZSA:Ce^{3+}$), possessing cubic symmetry with varied $Ce^{3+}$ concentrations, was synthesized using the solid-state reaction method. The samples were characterized using X-ray diffraction (XRD), excitation spectra, emission spectra, thermal quenching, and decay curves. The cubic phase of $CGZSA:Ce^{3+}$ phosphor was confirmed via XRD analysis. The photoluminescence spectra of $CGZSA:Ce^{3+}$ phosphor demonstrated that the phosphor could be excited at the wavelength of 440 nm; a broad yellow emission band was centered at 541 nm. These results indicate that the phosphors are adequately excited by blue light and have the potential to function as yellow-emitting phosphors for applications in white light-emitting diodes.