• The Korean Journal of Ceramics
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• v.1 no.4
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• pp.204-208
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• 1995

The microstructure and electrical propetries were investigated for polycrystalline $Ba^{1-x}Sr_xTiO_3$(BST) thin films deposited on Pt/Ti/$SiO_2$(PTSS) and Pt/MgO(PM) substrates by metalorganic chemical vapor deposition (MOCVD). BST films on PTSS have coulmnar and porous structures, while on PM have an equiaxied and dense structure. The dielectric constant and a dissipation factor of BST films on PTSS and 20 fC/$\mu \textrm{cm}^3$ on PTSS and 12fC/$\mu \textrm{cm}^2$ on PM was obtained at an applied electric field of 0.06 MV/cm. Leakage current density of BST films on PM was smaller than that on PTSS. The leakage current density level was about $8\times10^{-8}A/\textrm{cm}^2$ at 0.04MV/cm.

• Proceedings of the KIEE Conference
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• 1990.07a
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• pp.462-464
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• 1990

We report the development of a surface discharge preionized KrF discharge Laser with a new type of high-brightness Corona preionizer using a segmented columnar $BaTiO_3$ dielectric. This Laser characteristic was higher value than that obtained with the conventional corona preionizer using a glass, $Al_2O_3ceramic$, Kapton film, or a Teflon insulator.

• Journal of the Korean Ceramic Society
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• v.40 no.4
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• pp.380-384
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• 2003

The effects of the mole concentrations of precursor solution on the microstructure and dielectric properties of sol-gel deposited $Ba_{0.85}$S $r_{0.15}$Ti $O_3$(BST) thin films have been investigated. The films were of single perovskite phase with strong (100) preferred orientation when grown on LaNi0$_3$ buffered Pt/Ti/ $SiO_2$Si substrates using a diluted precursor solution. Variation of the precursor solution concentration resulted in a different microstructure and, in turn, affected the tunability of the sol-gel deposited films. It was observed that leakage currents increased asymmetrically for the negative and positive bias voltage with decreasing thickness. Overall results suggest that those BST films have acceptable properties f3r applications as room-temperature tunable elements.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.9
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• pp.826-834
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• 2004

In this paper, we fabricated thick film monopole antennas using Bi$_2$O$_3$-doped BaTi$_4$$O_{9}$ ceramics for small size and broadband intenna. In the result, the high permittivity was fixed and the quality factor was also significantly decreased by the formation of secondary phase of Bi$_4$Ti$_3$O$_{12}$ repleced by addtion Bi. The antenna property influenced by the quality value more than the permittivity. The bandwidth of antenna was increased to 33 %. On the other hand, the gain was reduced to -4.3 dBi. Also radiation patterns were showed low dBi value by increasing of dielectric loss. Specially, Measured x-y plane radiation patterns was distorted as the dispersion of wavelength and high permittivity difference. But the result is showed execellent bandwidth because of low quality value in all formation range.nge.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.3
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• pp.274-279
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• 2024

Eu³⁺-doped BaZrO₃ (BaZrO₃:Eu³⁺) phosphor powders were prepared using a solid-state reaction by changing the molar concentration of Eu³⁺ within the range of 0.5 to 30 mol%. Irrespective of the molar concentration of Eu³⁺ ions, the crystal structures of all the phosphors were cubic. The excitation spectra of BaZrO₃:Eu³⁺ phosphors consisted of an intense broad band centered at 277 nm in the range of 230~320 nm. The emission spectra were composed of a dominant orange band at 595 nm arising from the ⁵D₀→⁷F₁ magnetic dipole transition of Eu³⁺ and two weak emission bands centered at 574 and 615 nm, respectively. As the concentration of Eu³⁺ increased from 0.5 to 10 mol%, the intensities of all the emission bands gradually increased, approached maxima at 10 mol% of Eu³⁺ ions, and then showed a decreasing tendency with further increase in the Eu³⁺ ions due to the concentration quenching. The critical distance between neighboring Eu³⁺ ions for concentration quenching was calculated to be 11.21 Å, indicating that dipole-dipole interaction was the main mechanism of concentration quenching of BaZrO₃:Eu³⁺ phosphors. The results suggest that the orange emission intensity can be modulated by doping the appropriate concentration of Eu³⁺ ions.

• Korean Journal of Materials Research
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• v.34 no.1
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• pp.34-43
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• 2024

New piezoelectric and triboelectric materials for energy harvesting are being widely researched to reduce their processing cost and complexity and to improve their energy conversion efficiency. In this study, BaTiO₃ films of various thickness were deposited on Ni foams by R.F. magnetron sputtering to study the piezoelectric and triboelectric properties of the porous spongy structure materials. Then piezoelectric nanogenerators (PENGs) were prepared with spongy structured BaTiO₃ and PDMS composite. The output performance exhibited a positive dependence on the thickness of the BaTiO₃ film, pushing load, and poling. The PENG output voltage and current were 4.4 V and 0.453 ㎂ at an applied stress of 120 N when poled with a 300 kV/cm electric field. The electrical properties of the fabricated PENG were stable even after 5,000 cycles of durability testing. The triboelectric nanogenerators (TENGs) were fabricated using spongy structured BaTiO₃ and various polymer films as dielectrics and operated in a vertical contact separation mode. The maximum peak to peak voltage and current of the composite film-based triboelectric nanogenerator were 63.2 V and 6 ㎂, respectively. This study offers new insights into the design and fabrication of high output nanogenerators using spongy structured materials.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.252-252
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• 2007

$Al_2O_3-TiO_2$(AT)ceramics shows great promise as a dielectric material for millimeter-wave use. The sintering temperature of AT ceramics was approximately $1450^{\circ}C$ and decreased to $900^{\circ}C$ with the addition of BaCu(B2O5) (BCB) ceramic powder. The presence, of the liquid phase was responsible for the decrease of the sintering temperature. The liquid phase is considered to have a composition similar to the BaO-deficient BCB. The Q-value initially increased with the addition of BCB, but decreased considerably when a large amount of BCB was added, because of the presence of the liquid phase. Good microwave dielectric properties of $Q{\times}f\;=\;16,200\;GHz$, ${\varepsilon}_r\;=\;9$ and ${\tau}_f\;=\;-4\;ppm/^{\circ}C$ were obtained for the 20.0 mol% BCB-added AT ceramics sintered at $900^{\circ}C$ for 2 h.

• Journal of Electrical Engineering and Technology
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• v.9 no.1
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• pp.273-279
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• 2014

Hexagonal Ba-ferrites are widely suggested as materials for small antennas. In this paper, the sintering behavior and magneto-electric properties of $Ba_3Co_{2-2x}Mn_{2x}Fe_{24}O_{41}$ ($0.1{\leq}x{\leq}0.5$) ceramics were investigated for small antenna application. All samples of $Ba_3Co_{2-2x}Mn_{2x}Fe_{24}O_{41}$ ceramics were prepared by the solid-state reaction method and sintered at $1250^{\circ}C$. From the XRD patterns of the sintered $Ba_3Co_{2-2x}Mn_{2x}Fe_{24}O_{41}$ceramics, the Z-type phases were found to be the main phases. The real part of permittivity and permeability of the $Ba_3Co_{2-2x}Mn_{2x}Fe_{24}O_{41}$ceramics decreased with frequency. On the other hand, loss tangents of permittivity and permeability tended to behave opposite to real part of permittivity and permeability. The real part of permeability was affected by Mn additions. The real part of permittivity, the loss tangent of permittivity and the real part of permeability, the loss tangent of permeability of $Ba_3Co_{0.2}Mn_{0.8}Fe_{24}O_{41}$ ceramics were 19.774, 0.176 and 15.183, 0.073, respectively, at 510 MHz. In order to investigate the effect of magneto-dielectric ceramics on antenna, PIFA (Planar Inverted F Antenna) was simulated with CST (Computer Simulation Technology). The operating frequency of antenna was decreased without considerable change of bandwidth by using the $Ba_3Co_{0.2}Mn_{0.8}Fe_{24}O_{41}$ ceramics as the carrier.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.15 no.1
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• pp.67-74
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• 2002

A phosphor for Plasma Display Panel, BaMgAl$_{10}$ O$_{17}$ :Eu$^{2+}$, showing a blue emission band at about 450nm was prepared by a solid-state reaction using BaCO$_3$, $Al_2$O$_3$, MgO, Eu$_2$O$_3$ as starting materials wish flux AlF$_3$. The study of the behaviour of Eu in BAM phosphor was carried out by the photoluminescence spectra and the Rietveld method with X-ray and neutron powder diffraction data to refine the structural parameters such as lattice constants, the valence state of Eu, the preferential site of Mg atom and the site fraction of each atom. The phenomenon of the concentration quenching was abound 2.25~2.3wt% of Eu due to a decrease in the critical distance for energy transfer of inter-atomic Eu. Through the combined Rietveld refinement, R-factor, R$_{wp}$, was 8.11%, and the occupancy of Eu and Mg was 0.0882 and 0.526 at critical concentration. The critical distance of Eu$^{2+}$ in BAM was 18.8$\AA$ at 2.25% Eu of the concentration quenching. Furthermore, c/a ratio was decreased to 3.0wt% and no more change was observed over that concentration. The maximum entropy electron density was found that the modeling of $\beta$-alumina structure in BaMgAl$_{10}$ O$_{17}$ :Eu$^{2+}$correct coincided showing Ba, Eu, O atoms of z= 1/4 mirror plane.e.ane.e.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.59-66
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• 2013

Opal glass samples having different chemical compositions were synthesized and transparent glass was obtained after melting. The effects of $TiO_2$, $BaF_2$, and $CeO_2$ content on the color of the opal glass were studied by observing images of the opal samples and analyzing the results via ultraviolet visible spectroscopy and color spectrometry. The aesthetic properties of the opal glass were determined by studying the transmittance of visible light in the 400 nm to 700 nm range. The basic chemical composition of opal glass was $SiO_2$ 52.9 wt%, $Al_2O_3$ 12.35 wt%, $Na_2CO_3$ 15.08 wt%, $K_2CO_3$ 10.35 wt%, $Ca_3(PO)_4$ 4.41 wt%, $MgCO_3$ 1.844 wt%, $LiCO_3$ 2.184 wt%, and $TiO_2$ 0.882 wt%. The glass samples were prepared by varying the weight percentage of $TiO_2$, $BaF_2$, and $CeO_2$. The transmittance of visible light was decreased from 95 % to 75 % in the glass samples in which $TiO_2$ content was increased from 0 to 3.882 wt%. In the blue spectrum region, as the content of $TiO_2$ increased, the reflectance value was observed to become higher. This implies that $TiO_2$ content induces more crystal formation and has an important effect on the optical properties of the glass. The opalescence of opal samples that contained $CeO_2$ or $BaF_2$ is stronger than that in the samples containing $TiO_2$. Opal glass samples comprising $TiO_2$ had tetragonal lattice structures; samples including $CeO_2$ as an additive had cubic lattice structures (FCC, $CeO_2$).