• Journal of the Korean Applied Science and Technology
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• v.27 no.1
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• pp.29-36
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• 2010

The effects of La addition to Ni/$CeO_2$ methane partial oxidation catalysts were investigated. Catalysts were prepared by the impregnation and urea methods. In the preparation of catalysts, La content was changed from 1 wt% to 3wt%. Catalysts that contain 2wt% La showed the highest methane conversion of about 80% and CO selectivity of 84% and $H_2$ selectivity of 70%. This result may be stemmed from that, when La content is 2wt%, a fluorite oxide-type structure is well formed and carbon deposition is also decreased. Among the catalysts, 2.5wt% Ni/Ce(La)Ox showed the highest catalytic activity. From the experiment of changing reaction temperature with 2.5wt% Ni/Ce(La)Ox catalyst, it was found that the optimum reaction temperature is $750^{\circ}C$ and at this temperature methane conversion was about 90%, CO and $H_2$ selectivities were 94 and 80%, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.8
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• pp.830-834
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• 2004

In this study, lead-free pirzoelectric ceramics were investigated for pressure sensor applications as a function of the amount of ${La}_2{O}_3$ addition at $Bi(Na, K)Ti{O}_3-SrTi{O}_3$system. With increasing the amount of addition, the density and dielectric constant increased up to 0.9 wt% ${La}_2{O}_3$ addition and decreased above 0.9 wt% ${La}_2{O}_3$addition. Electromechanical coupling factor( $K_{P}$) showed the maximum value at 0.2 wt% ${La}_2{O}_3$addition and decreased above 0.2 wt% ${La}_2{O}_3$ addition. Electromechanical coupling $factor{(K)}_P$, density, dielectric constant$(\varepsilon_\Gamma)$, piezoelectric constant$(d_33)$ and curie temperature$(T_C)$ showed optimum value of 0.40, 5.75 g/㎤, 768, 215 pC/N and 320 $^{\circ}C$ at 0.2 wt%${La}_2{O}_3$addition, respectively.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.33A no.2
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• pp.87-95
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• 1996

We have studied the effects of La concentration on the optical and electrical properties of lead lanthanum titanate (PLT) thin films by using sol-gel method. Both the optical and electrical properties are greatly affected by the La concentration. The refreactiv eindices of the films varied from 2.23 to 1.93 with varying La concentration in the range from 15 to 33 mol%. The dielectric constants of the films vary form 340 to 870 with varying La concentration in the range form 15 to 33 mol%. Hysteresis loop becomes slimmer with the increase of La concentration form 15 to 28mol% and little fatter again with the increase of La concentration form 28 to 33 mol%. Among the films investigated in this research, PLT(28) thin film shows the best dielectric properties for the application to the dielectrics of ULSI DRAM's. At the frequency of 100Hz, the dielectric constant and the loss tangent of PLT(28) thin films are 940 and 0.08 respectively. Its leakage current density at 1.5${\times}10^{5}$V/cm is 1${\times}10^{-6}A/cm^{2}$. The comparision between the simulated and the experimental curves for the switching transient characteristics shows that PLT (28) thin films behaves like normal dielectrics.

• The Journal of Natural Sciences
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• v.15 no.1
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• pp.35-46
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• 2005

$LaFeO_3$ and substituted $LaFeO_3$ mixed oxides were prepared by Citrate and Cyanide method in air $850^{\circ}C$/24h. These oxides of orthorhombic perovskite were characterized by XRD and IR, but substituted $LaFeO_3$ with 0.5mol Cu at B site was not obtained single phase. Also, reduction reaction of un-substituted $LaFeO_3.17$ were two steps but each site substituted oxides were three steps reactions. These means that new reduction step of each site substituted oxides were atributed tot dopant.

• Journal of the Korean Ceramic Society
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• v.25 no.3
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• pp.268-276
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• 1988

Ba or La-Substituted lead niobate $(Pb_{1-x}Ba_x)_{1-y}La_{2y/3}Nb_2O_6$(PBLN), powders having needle shape are prepared by flux method using KCl and the effect of Ba or La substitution on morphology of obtained powders is examined. From these needle shape powders, grain-oriented ceramics are made by doctor-blade method and two-stage hot-pressing technique. The dielectric, piezoelectric and optical properties of the ceramics are also investigaated. Heating condition and the amount of substituted Ba or La have remarkable effects have large anisotropy in both permittivity and coupling factor depending on the pressing direction.

• Korean Journal of Optics and Photonics
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• v.7 no.2
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• pp.162-166
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• 1996

We report a fiber optic interferometric electric field sensor that utilizes electrostrictive ceramics-1%, 2%, 3%, La-doped 0.9MN/0.1PT, respectively-as the transducing elements. It is also experimentally observed that 3% La-doped PMN/PT among the three elements has the largest electrostrictive coefficient $M=3.87{\times}10^ {-16}(m/V)^2$ at 3.38 kHz and displays small hysteresis. The optical fiber sensor with the 3% La-doped PMN/PT exhibits minimum detectable field of 2.08(V/m)/ $\sqrt{Hz}$ and has a good linearity over the dynamic range 40 dB.

• Electrical & Electronic Materials
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• v.9 no.4
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• pp.379-384
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• 1996

The microwave dielectric properties of (I-x)CaTiO$_{3}$-xLaAIO$_{3}$ were investigated. The solid solution of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ had the perovskite structure in the range of all compositions. The crystal system of (1-x)CaTiO$_{3}$-xLaAIO$_{3}$ was transformed to orthorhombic(x.leq.0.4), psudo-cubic(x=0.5), and rhombohedral (x.geq.0.7) in turn, as the amount of LaAIO$_{3}$ increased. The dielectric constant and temperature coefficient of resonant frequency of solid solution were decreased with the content of LaAIO$_{3}$, whereas, the value of Q . f$_{o}$ was increased. The microwave dielectric material having Q . f$_{o}$ = 32, 500, .epsilon.$_{r}$ = 42, and .tau.$_{f}$ = 5 ppm/.deg. C was obtained from the 0.35CaTiO$_{3}$-0.65LaAIO$_{3}$ composition sintered at 1600.deg. C for 4hrs.hrs.hrs.

• Journal of the Korean Chemical Society
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• v.21 no.2
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• pp.89-93
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• 1977

Faujasite type zeolite synthesized from kaolin minerals was cation-exchanged and the catalytic activities of $1-Butene{\rightarrow}2-butene$ took place readily even on zeolites having no strong acid sites. The order of activity for isobutene formation was La > H > Zn > Na-faujasite, La-faujasite showing much higher activity. The same trend was observed for propylene formation except that both La-and H-faujasite showed comparable activity. The results seem to indicate that the activities for 1-buten cracking and isomerization on zeolite are directly related to the strength and concentration of the acid sites on zeolites.

• Food Science of Animal Resources
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• v.18 no.1
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• pp.9-18
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• 1998

This study was performed to obtain a large quantity of $\alpha$-lactalbumin ($\alpha$-LA) from milk by an improved separation and purification method. Functional properties-solubility viscosity, emulsifying activity, foamability surface hydrophobicity and gelation-of the purified $\alpha$-LA were investigated, $\alpha$-LA was purified in a large quantity by DEAE-Sephacel chromatography using 0.15M NaCl in 20mM Tris-HCl buffer(pH 7.2), as an eluent. The yield and purity of the purified $\alpha$-LA were 23.6%, 92.5%, respect-ively. The solubility viscosity and emulsifying activity of the purified $\alpha$-LA were 92.2$\pm$2% 3.46$\pm$0.19 cP and 345$\pm$5.0m^2$-/g respecively. The foamability of $\alpha$ -LA was 762 after 5min whipping which was lower than that of WPC and showed decreasing tendency with whipping time. The relative surface hydrophobicity of the $\alpha$-LA was formed when a 10% $\alpha$-LA solution containing 100mM NaCl and 20 mM $CaCl_2$ was heated at 92$^{\circ}C$for 40min. The $\alpha$-LA gel showed 31.5 as hardness and showed low springiness and cohesiveness.

• Transactions on Electrical and Electronic Materials
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• v.7 no.3
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• pp.123-128
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• 2006

The microstructure and electrical properties of the varistors, which are composed of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-La_2O_3-based$ ceramics, were investigated for different $La_2O_3$ contents. The increase of $La_2O_3$ content led to more densified ceramics, whereas abruptly decreased the nonlinear properties by incorporating beyond 1.0 mol%. The highest nonlinearity was obtained from 0.5 mol% $La_2O_3$, with the nonlinear coefficient of 81.6 and the leakage current of $0.2{\mu}A$. The increase of sintering time and temperature greatly decreased the nonlinear properties. As the $La_2O_3$ content increased, the donor density increased from $0.64\times10^{18}/cm^3\;to\;16.89\times10^{18}/cm^3$ and the barrier height greatly decreased with increasing $La_2O_3$ content, reaching a maximum (1.47 eV) in 0.5 mol% $La_2O_3$.