• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.6
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• pp.455-459
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• 2001

In this paper, the dielectric and pizoelectric properties of 0.05Pb(M $n_{04}$ $W_{0.2}$N $b_{0.4}$) $O_3$-0.95(PbZ $r_{x}$ $Ti_{1-x}$ ) $O_3$+yN $b_2$ $O_{5}$ , are investigated as a function of the mole ratio of Zr and the amount of N $b_2$ $O_{5}$ . Also, the phase is analyzed by XRD. When the mole ratio of Zr is 0.51, the electromechanical coupling coefficient( $k_{p}$ ), relative dielectric constant ($\varepsilon$$^{T}$ $_{33}$ /$\varepsilon$$_{0}$ ), piezoelectric stain constrain ( $d_{33}$ and dielectric loss tangent show maximum, while the mechanical quality factor shows minimum value ; $k_{p}$ =56.5%, $d_{33}$ =258pC/N, $\varepsilon$$^{T}$ $_{33}$ /$\varepsilon$$_{0}$ =1170, $Q_{m}$ =1150, tan$\delta$=0.51%. At that composition, MPB which rhombohedral and tetragonal phase coexist in this ternary system is shown by the results of XRD analysis. Also, when the amount of N $b_2$ $O_{5}$ is 0.3wt%, the mechanical quality factor is increased to about 2000. The phase transition temperature of the ternary piezoelectric ceramic system showed about 35$0^{\circ}C$.TEX>.>.>.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2005.11a
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• pp.35-38
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• 2005

The Objective of this work was to design Composite Antenna Structures (CAS) and investigate impact behavior of CAS which was various curvature. This term, CAS, indicates that structural surface becomes antenna. Constituent materials were selected considering electrical properties, dielectric constants and tangent loss as well as mechanical properties. For the antenna performance, microstrip antenna layers inserted into structural layers were designed for satellite communication at the resonant frequency of 12.5 GHz and final demonstration article was. After making five kinds of curved CAS, which radii of curvature are flat, 200, 150, 100, 50 mm. The antenna performance changed in accordance with variation of curvature. The Reflection coefficient was independent of curvature but the gain decreased with the radius of curvature. The impact test equipment was Dyna-8250 drop weight tester. The impact characteristic in accordance with curvature is maximum absorb energy is same each other. The impact energy was 8.5 J. For various Impact energy test, five energy levels 3 J, 5 J, 7 J, 10 J, 20 J were used. The performance of impact damaged antenna was estimated by measuring the return loss and the radiation pattern. It was revealed that the performance of antenna was not related to the impact damage. Because the impactor did not damage the patch directly. CAS have good impact stability for the antenna performance.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.10a
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• pp.453-456
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• 2009

In this paper, a Microstrip antenna for wireless LAN is designed in HyperLAN 5GHz. The IEEE 802.11a have allocated HyperLAN band. We proposed CPW-fed antenna structure for compact antenna. This structure shows that a ground plane and a patch plane are existed at one layer. The proposed antenna is designed on FR-4 substrate with a relative dielectric constant 4.3, thickness of 1.5mm and tangent loss 0.02. The designed antenna shows that VSWR is below 2 and has good return loss below -10dB over the 5.725~5.825GHz bandwidth with HyperLAN.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.12
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• pp.2823-2830
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• 2014

The antenna miniaturization technique involves the increment of the electrical length of the resonator the variation of the physical appearance of the antenna. The most typical method of size reduction is designing helical antenna, meander antenna, and fractal antenna. Size reduction using fractal antenna is proposed in this paper. Fractal koch curve has been etched in microstrip patch antenna to downsize the antenna at ISM (Industrial Scientific and Medical) frequency band of 2.45 GHz koch curve microstrip patch antenna ha FR4 epoxy substrate with dielectric constant 4.7, loss tangent equal to 0.02 and dielectric high of 1.6 mm. The designed antenna is fabricated using etching process. The fabricated antenna has return loss of 2.45 GHz, VSWR of 1.1492, and impedance is matched to $46{\Omega}$.

• Journal of the Korean Ceramic Society
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• v.45 no.7
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• pp.411-417
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• 2008

Aerosol Deposition Method (ADM) is a novel technique to grow ceramic thick films with high density and nano-crystal structure at room temperature. $^{1,2)}$ For these unique advantages of ADM, it would be applied to the fabrication process of 3-D integration ceramic modules effectively. However, it is critical to control the properties of starting powders, because a film formation through ADM is achieved by impaction and consolidation of starting powders on the substrates. We fabricated alumina thick films by ADM for the application to integral substrates for RF modules. When the as-received alumina powders were used as a starting material without any treatments, it was observed that the dielectric properties of as-deposited alumina films, such as relative permittivity and loss tangent, showed high dependency on the frequency. In this study, some techniques of powder pre-treatments to improve the dielectric properties of alumina thick films will be shown and the effects of starting powders on the properties of AD films will be discussed.

• Korean Journal of Materials Research
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• v.4 no.3
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• pp.312-318
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• 1994

In this paper the breakdown and dielectric characteristics of purified transformer oil dissolved with $SF_6$ Gas are investigated with a few decade MHz frequency voltage. The results are as follows. 1) High frequency current is a approximately proportional to the square root of high frequency voltage in purified transformer oil. 2) As frequency increase breakdown voltage decrease inversely proportional to the square root of frequency and the high frequency breakdown voltage is lower about 35 percentage than that of AC 3) The breakdown voltage of high frequency has a little increase with the pressure increase of dissolved $SF_6$, Air and Ar Gas. 4) As voltage freguency increases the value of the dielectric loss tangent has increased almost exponentially and the dielectric constant ($\varepsilon$) has tended to decrease with a slope[0.6% MHz]. 5) When dissolved with $SF_6$ Gas, oil electrical characteristics has more increased about 25% than in Air or Ar gas with high voltage frequency.

• Proceedings of the IEEK Conference
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• 2000.06b
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• pp.28-31
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• 2000

In this paper, the effects of La addition of PLZT(x/30/70) thin films Prepared by sol-gel method are investigated for NVFRAM application. The tetragonality (c/a), the grain size, and the surface roughness of PLZT thin films decrease with an increase of La concentration. As the La concentration increases, the dielectric constants at 10 kHz increase from 450 to 600, while the loss tangent decrease from 0.075 to 0.025. Also, the leakage current density at 100kV/cm decrease from 5.83$\times$10$^{-7}$ to 1.38$\times$10$^{-7}$ 4/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$170kV/cm, the remanent polarization and the coercive field of PLZT thin films with La concentration from 0 to 10㏖％ decrease from 20.8 to 10.5 $\mu$C/cm and from 54.48 to 32.12kV/cm, respectively. After a fatigue measurement by applying 10$^{9}$ square pulses with $\pm$5V, the remanent polarizations of PLZT thin films with 0 and 10㏖％ La concentration decrease about 64 and 42 ％ from initial state. In the results of retention measurement after 10$^{5}$ s, PLZT thin films with 0 to 10mo1％ La concentration show that the remanent polarization is decreased about 43％ and 9％ from initial state, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.179-179
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• 2009

This is for the electrical characterization by IDC pattern using BST$(Ba_{0.5}Sr_{0.5}TiO_3)$ thin film. BST materials had been chosen for high frequency applications due to it's high permitivity and tunability. The BST thin films have been deposited on $Al_2O_3$ Substrates by Nd-YAG pulsed laser deposition with a 355nm wavelength at $700\;^{\circ}C$. The post deposition annealing at $750^{\circ}C$ in flowing $O_2$ atmosphere for 1 hours. The capacitance of IDC patterns have been measured from 1 to 10 GHz as a function of electric field ($\pm40$ KV/cm) at room temperature using inter-digital Au electrodes deposited on top of BST. The IDC patterns have three type of fingers number. For the 10 pairs finger was the best capacitance onto $Al_2O_3$ substrate. The capacitance was 0.9pF. Also Dielectric constant was been 351 at 100 mTorr and annealing temperature $750^{\circ}C$ for 1 hour. The loss tangent was been 0.00531.

• Transactions on Electrical and Electronic Materials
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• v.15 no.2
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• pp.100-102
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• 2014

$Ag(Ta,Nb)O_3$ materials have a perovskite structure with a low loss tangent. These materials have been widely researched for their applications as high-frequency, passive components. Also, $Ag(Ta,Nb)O_3$ materials have weak frequency dispersion with high dielectric permittivity which gives them enormous potential for use in electronic components, including the filters, and embedded capacitors. Therefore, our research will discuss the structural and electrical relaxation properties of $Ag(Ta_{0.8}Nb_{0.2})O_3$ ceramics for device applications. We will investigate using X-ray diffraction to understand their structural properties and will analyze voltage dependent leakage current and timedependent relaxation behavior to understand their material properties.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.195-198
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• 1999

A Bi$_4$Ti$_3$O$_{12}$ (BIT) thin film is prepared by sol-gel method using acetate precursors and evaluated whether it could be applied to NVFRAM. The drying and the annealing temperature are 40$0^{\circ}C$ and $650^{\circ}C$, respectively and they are determined from the DT-TG analysis. The BIT thin film deposited on Pt/Ta/SiO$_2$/Si substrate shows orthorhombic perovskite phase. The grain size and the surface roughness are about 100 nm and 70.2$\AA$, respectively. The dielectric constant and the loss tangent at 10 KHz are 176 and 0.038, respectively, and the leakage current density at 100㎸/cm is 4.71$mutextrm{A}$/$\textrm{cm}^2$. In the results of hysteresis loops measured at $\pm$250㎸/cm, the remanent polarization (Pr) and the coercive field (Ec) are 5.92$mutextrm{A}$/$\textrm{cm}^2$ and 86.3㎸/cm, respectively. After applying 10$^{9}$ square pulses of $\pm$5V, the remanent polarization of the BIT thin film decreases as much as about 33% from 5.92 $\mu$C/$\textrm{cm}^2$ of initial state to 3.95 $\mu$C/$\textrm{cm}^2$.