• Journal of Ceramic Processing Research
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• 제13권spc2호
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• pp.163-165
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• 2012

Impedance spectroscopy informs electrical properties of materials as accumulated charges, contact status between electrode and organic materials. We carried out impedance spectroscopy of organic light-emitting diodes as ITO/Alq3(60 nm)/Al on temperatures from 10 K to 300 K. The result described Z'-Z" plot, cole-cole plot and dielectric relaxation time τ. Z'-Z" plot means that real and imaginary part of materials in organic and electrode by frequencies and temperature. Z' as real part of impedance by applied frequency depending on temperature shows the plateau in low frequency region as Rs+ Rp and over 100 kHz in high frequency region as Rs. Cole-cole plot shows resistance of materials in equivalent circuit of the device by temperatures. And equivalent circuit and dielectric relaxation could be accomplished by using the complex impedance analysis.

• KIEE International Transactions on Electrophysics and Applications
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• 제4C권3호
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• pp.81-89
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• 2004

Frequency Domain Spectroscopy (FDS) measurements were performed on pressboard samples containing different moisture contents and on insulation system of power transformers. The results were used for evaluating sensitivity of the so-called X - Y model, which is applied for estimating moisture content in transformer insulation using the results of FDS measurements. Based on the observations of this analysis a simplified model, called X model, was introduced in which the presence of spacers in transformer insulation has been neglected. Finally, reliability of the X model was assessed by comparing estimates of moisture contents based on FDS measurements on field installed power transformers with moisture contents obtained from chemical analyses of their oil samples.

• Advances in materials Research
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• 제2권3호
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• pp.141-153
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• 2013

Nanocrystalline Barium niobate ($BaNbO_3$) has been synthesized by a novel auto-igniting combustion technique. The X-Ray diffraction studies reveals that $BaNbO_3$ posses a cubic structure with lattice constant $a=4.071{\AA}$. Phase purity and structure of the nano powder are further examined using Fourier-Transform Infrared and Raman spectroscopy. The average particle size of the as prepared nano particles from the Transmission Electron Microscopy is 20 nm. The UV-Vis absorption spectra of the samples are recorded and the calculated average optical band gap is 3.74eV. The sample is sintered at an optimized temperature of $1425^{\circ}C$ for 2h and attained nearly 98% of the theoretical density. The morphology of the sintered pellet is studied with Scanning Electron Microscopy. The dielectric constant and loss factor of a well-sintered $BaNbO_3$ at 5MHz sample is found to be 32.92 and $8.09{\times}10^{-4}$ respectively, at room temperature. The temperature coefficient of dielectric constant was $-179pp/^{\circ}C$. The high dielectric constant, low loss and negative temperature coefficient of dielectric constant makes it a potential candidate for temperature sensitive dielectric applications.

• 한국재료학회지
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• 제29권12호
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• pp.753-756
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• 2019

Orthorhombic dysprosium manganite DyMnO₃ with single phase is synthesized using solid-state reaction technique and the crystal structure and dielectric properties as functions of temperature and frequency are investigated. Thermally activated dielectric relaxations are shown in the temperature dependence of the complex permittivity, and the respective peaks are found to be shifted to higher temperatures as the measuring frequency increases. In Arrhenius plots, activation energies of 0.32 and 0.24 eV for the high- and low-temperature relaxations are observed, respectively. Analysis of the relationship between the real and imaginary parts of the permittivity and the frequencies allows us to explain the dielectric behavior of DyMnO₃ ceramics by the universal dielectric response model. A separation of the intrinsic grain and grain boundary properties is achieved using an equivalent circuit model. The dielectric responses of this circuit are discerned by impedance spectroscopy study. The determined grain and grain boundary effects in the orthorhombic DyMnO₃ ceramics are responsible for the observed high- and low-temperature relaxations in the dielectric properties.

• Advances in materials Research
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• 제2권2호
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• pp.99-109
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• 2013

In the present investigation, nanocomposite films with poly(methyl methacrylate) (PMMA) as a polymer matrix and barium titanate as a filler were prepared by solution casting method. Barium titanate nano particles were prepared using Ti(IV) triethanolaminato isopropoxide and hydrated barium hydroxide as precursors and tetra methyl ammonium hydroxide (TMAH) as a base. The nanocomposite films were characterized using XRD, FTIR, SEM and dielectric spectroscopy techniques. Dielectric measurements were performed in the frequency range 100 Hz-10 MHz. Dielectric constant of nanocomposites were found to depend on the frequency, the temperature and the filler fraction. Dissipation factors were also influenced by the frequency and the temperature but not much influenced by the filler fractions. The 10 wt% of BT-PMMA nanocomposite had the lowest dielectric constant of 3.58 and dielectric loss tangent of 0.024 at 1MHz and $25^{\circ}C$. The dielectric mixing model of Modified Lichtenecker showed the close fit to the experimental data.

• 한국전기전자재료학회논문지
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• 제29권9호
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• pp.565-570
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• 2016

In this work, the complex permittivity of epoxy resins is measured. Epoxy resins, epoxy with micro size fillers and epoxy with micro+nano alumina composites have been evaluated for dielectric properties according to frequency variation. The dielectric spectroscopy measurement and analyses are carried out in the frequency range of $10^{-2}Hz$ to 1MHz and constant to room temperature. The results of dielectric loss suggest that significant improvement in the electrical performance can be expected by using samples containing nano and micro fillers mixture when compared to materials containing only microfillers. As the result, we verified the specific characteristics of dielectric permittivity and dielectric loss namely, relative permittivity become low with improving dispersibility of nano+micro mixture composites and become rise with agglomerate of nano particles.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.381-381
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• 2010

$(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films as gate dielectrics have been proposed to overcome the problems of tunneling current and degradation mobility inachieving a thin equivalent oxide thickness. An extremely thin $SiO_2$ layer is used in order to separate the carrier in MOSFET channel from the dielectric field fluctuation caused by phonons in the dielectric which decreases the carrier mobility. The electronic and optical properties influenced the device performance to a great extent. $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric films on p-Si (100) were grown by atomic layer deposition method, for which the conduction band offsets, valence band offsets and band gapswere obtained by using X-ray photoelectron spectroscopy and reflection electron energy loss spectroscopy. The band gap, valence and conduction band offset values for $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ dielectric thin film, grown on Si substrate were about 5.34, 2.35 and 1.87 eV respectively. This band alignment was similar to that of $ZrO_2$. In addition, The dielectric function (k, $\omega$), index of refraction n and the extinction coefficient k for the $(ZrO_2)_{0.66}(HfO_2)_{0.34}$ thin films were obtained from a quantitative analysis of REELS data by comparison to detailed dielectric response model calculations using the QUEELS-$\varepsilon$(k, $\omega$)-REELS software package. These optical properties are similar with $ZrO_2$ dielectric thin films.

• 한국광학회:학술대회논문집
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• 한국광학회 2002년도 하계학술발표회
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• pp.172-173
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• 2002

As feature sizes of circuits and devices approach 100 m and chip frequencies climb into the upper gigahertz to terahertz range, it becomes increasingly important to have a convenient method of characterizing properties of thin dielectric films in the GHz to THz frequency range [1]. To measure the dielectric and optical properties of materials at THz frequency, a TH2 time-domain spectroscopy has been utilized during past decade. (중략)

• The Korean Journal of Ceramics
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• 제2권2호
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• pp.76-82
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• 1996

PLZT ceramics having two nominal compositions, $Pb_{1-3x/2}La_xV_{x/2}(Zr_{03}Ti_{03})O_3$ and $Pb_{1-x}La_x(Zr_{0.2}Ti_{0.5})_{1-x/4}V_{x/4}O_3$ (V: vacancy) with x=0.00~0.30, were prepared. The physical, structural, and dielectric properties were investigated by X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and measurements of bulk density and dielectric constant. The two series with A-stie and B-site vacancies showed different physical, structural, dielectric properties, and, specially, Curie temperature. In comparison to PLZT with B-site vacancies, PLZT with A-site vacancies showed high Curie temperatures and low maxima of dielectric constant. Consequently, it is evident that the properties of PLZT ceramics depend on the vacancy formula adopted as a batch composition in preparation.

• Macromolecular Research
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• 제17권8호
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• pp.585-590
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• 2009

The cure behaviors, dielectric characteristics and fracture toughness of diglycidylether of bisphenol-A (DGEBA)/poly(ethylene terephthalate) (PET) blend system were investigated. The degree of conversion for the DGEBA/PET blend system was measured using Fourier transform infrared (FTIR) spectroscopy. The cure kinetics were investigated by measuring the cure activation energies ($E_a$) with dynamic differential scanning calorimetry (DSC). The dielectric characteristic was examined by dielectric analysis (DEA). The mechanical properties were investigated by measuring the critical stress intensity factor ($K_{IC}$), critical strain energy release rate ($G_{IC}$), and impact strength test. As a result, DGEBAIPET was successfully blended. The Ea of the blend system was increased with increasing PET content to a maximum at 10 phr PET. The dielectric constant was decreased with increasing PET content. The mechanical properties of the blend system were also superior to those of the neat DGEBA. These results were attributed to the increased cross-linking density of the blend system, resulting from the interaction between the epoxy group of DGEBA and the carboxyl group of PET.