• Macromolecular Research
• /
• v.17 no.10
• /
• pp.785-790
• /
• 2009

In this paper, the relaxation behavior of the regenerated silk fibroin (SF) films was investigated using dielectric thermal analysis (DETA), and compared with the dynamic mechanical behavior obtained from dynamic mechanical thermal analysis (DMTA), in order to gain a better understanding of the characteristics of dielectric behavior of SF film and identify the differences between the two analyses. Compared to DMTA, DETA exhibited a higher sensitivity on the molecular relaxation behaviors at low temperature ranges that showed a high $\gamma$-relaxation peak intensity without noise. However, it was not effective to examine the relaxation behaviors at high temperatures such as $\alpha-$ and ${\alpha}_c$-relaxations that showed a shoulder peak shape. On the contrary, DMTA provided more information regarding the relaxation behaviors at high temperatures, by exhibiting the changes in width, intensity and temperature shift of the $\alpha$-relaxation peak according to various crystallinities. Conclusively, DETA and DMTA can be utilized in a complementary manner to study the relaxation behavior of SF over a wide temperature range, due to the different sensitivity of each technique at different temperatures.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2001.07a
• /
• pp.470-473
• /
• 2001

In this study, 70/30 mol% P(VDF-TrFE) copolymer thin films were prepared by physical vapor deposition, and dielectric properties with frequency were investigated. From results of TA(Thermal Analysis), the Curie transition temperature and melting temperature were observed at 118.8$^{\circ}C$ and 146$^{\circ}C$, respectively. Therefore, while thin films were prepared, the substrate temperature was varied from 30$^{\circ}C$ to 90$^{\circ}C$. The dielectric constant decreased with increasing frequency. At measuring frequency of 1kHz, the relative dielectric constant increased from 3.643 to 23.998 with increasing substrate temperature from 30$^{\circ}C$ to 90$^{\circ}C$. As a result of dielectric loss factor, ${\alpha}$-relaxation and ${\beta}$-relaxation were observed near at 100Hz and 1MHz, respectively. And the magnitude of ${\alpha}$-relaxation decreased and that of ${\beta}$-relaxation increased with increasing substrate temperature.

• Journal of the Korean Chemical Society
• /
• v.56 no.4
• /
• pp.416-423
• /
• 2012

Using time domain reflectometry, the complex dielectric spectra between 10 MHz to 20 GHz has been measured in the whole composition range at 10, 20, 30 and $40^{\circ}C$ for the binary mixtures of ethylene glycol and dimethyl sulfoxide. For all the mixtures, only one dielectric loss peak was observed in this frequency range. The relaxation in these mixtures can be described by a single relaxation time using the Debye model. A systematic variation is observed in dielectric constant (${\varepsilon}_0$) and relaxation time (${\tau}$). The excess permittivity (${\varepsilon}^E$), excess inverse relaxation time $(1/{\tau})^E$, Kirkwood correlation factor (g) and thermodynamic parameters viz. enthalpy of activation (${\Delta}H$) and Gibbs free energy of activation (${\Delta}G$) have been determined, to confirm the formation of hydrogen bonded homogeneous and heterogeneous cooperative domains, the dynamics of solute - solute interaction and the hindrance to molecular rotation in the hydrogen bonded glass forming ethylene glycol - dimethyl sulphoxide system.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.9
• /
• pp.1403-1407
• /
• 2004

Dielectric relaxation measurements on 3-nitrotoluene (3-NT) mixture of dimethylacetamide (DMA), dimethylformamide (DMF) and dimethysulphoxide (DMSO) have been carried out across the entire concentration range using Time domain reflectometry technique at 15, 25, 35 and $45^{\circ}C$ over the frequency range from 10 MHz to 20 GHz. For all the mixtures, only one dielectric loss peak was observed in this frequency range and the relaxation in these mixtures can be well described by a single relaxation time using Debye model. Bilinear calibration method is used to obtain complex permittivity ${\varepsilon}^{*}({\omega})$ from complex reflection coefficient ${\rho}^{*}({\omega})$ over frequency range 10 MHz to 20 GHz. The excess permittivity, excess inverse relaxation time, Kirkwood correlation factor, molar energy of activation are also calculated for these mixtures to study the solute-solvent interaction.

• JSTS:Journal of Semiconductor Technology and Science
• /
• v.14 no.5
• /
• pp.543-548
• /
• 2014

In this paper, the dielectric relaxation and reliability of high capacitance density metal-insulator-metal (MIM) capacitors using $Al_2O_3-HfO_2-Al_2O_3$ and $SiO_2-HfO_2-SiO_2$ sandwiched structure under constant voltage stress (CVS) are characterized. These results indicate that although the multilayer MIM capacitor provides high capacitance density and low dissipation factor at room temperature, it induces greater dielectric relaxation level (in ppm). It is also shown that dielectric relaxation increases and leakage current decreases as functions of stress time under CVS, because of the charge trapping effect in the high-k dielectric.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.11
• /
• pp.1231-1235
• /
• 2001

Pseudotetragonal ZrO0.75S whose space group is P212121 was synthesized and the cell dimensions were a=5.110(2) $\AA$, b=5.110(7) $\AA$, and c=5.198(8) $\AA.$ The space group P212121 seems to be resulted from lowering the symmetry of cubic ZrOS structure with P213 space group by lattice distortion due to the oxygen defects. In the distorted structure, bond shortening between metal-nonmetal by reduction of cell volume and alternation of Zr-Zr distance were observed. Dielectric constant and loss data of the bulk material in temperature range -170 to 20 $^{\circ}C$ and frequency range 50 Hz to 1 MHz showed that there was dielectric transition at around -70 $^{\circ}C$ originated from the relaxation of Zr-S segment. Comparing with ZrO2 exhibited the dielectirc constants, 9.0 at room temperature, ZrO0.75S showed high dielectric constant, k = 200.2 at 100 kHz. The activation energy of relaxation time due to dielectric relaxation of Zr-S was 0.47 eV (11.3 kcal/mole). According to the impedance spectra, ZrO0.75S showed more parallel circuit character between the resistance and capacitance components at the temperature (-70 $^{\circ}C)$ that the Zr-S dielectric relaxation was observed.

• Applied Science and Convergence Technology
• /
• v.24 no.3
• /
• pp.47-52
• /
• 2015

The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition $PbSc_{0.5}Nb_{0.5}O_3$, was prepared by conventional solid state synthesis. Conductance Y'(G), susceptance Y"(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent ${\gamma}$=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between $Sc^{3+}$ and $Nb^{5+}$ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and $900cm^{-1}$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2003.07b
• /
• pp.822-825
• /
• 2003

Maxwell displacement current (MDC) measurement has been employed to study the dielectric property of Langmuir-films. A method for determining the dielectric relaxation time $\tau$ of floating monolayers on water surface is presented. WC flowing across monolayers is analyzed using a rod-like molecular model. It is revealed that the dielectric relaxation time $\tau$ of monolayers in the isotropic polar orientational phase is determined using a liner relationship between the monolayer compression speed ${\alpha}$ and the molecular area Am. Compression speed ${\alpha}$ was about 30, 40, 50mm/min.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1998.06a
• /
• pp.173-176
• /
• 1998

We experimentally investigated the dielectric relaxation phenomena of a liquid crystal monolayers by the Displacement current techique and displacement current flowing across monolayers is analyzed using rod-like molecular model. It is revealed that the dielectric reaxation time $\tau$ of monolaters in the isotropic polar orientational phase is determined using a linear relashionship between the monolayers compression speed $\alpha$ and the molecular area. The dielectric relaxation time of phospholipid monolayers was examined on the basis of the analysis developed here.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2000.11a
• /
• pp.279-282
• /
• 2000

The displacement current measurement has been employed to study the dielectric properties of Langmuir films. A method for determining the dielectric relaxation time $\tau$ of floating monolayers on water surface is presented. The displacement current flowing across monolayers is analyzed using a rod-like molecular model. It's revealed that the dielectric relaxation time $\tau$ of monolayers in the isotropic polar orientational phase is determined using a liner relationship between the monolayers compression speed $\alpha$ and the molecular maximum area $A_{m}$. The compression speed $\alpha$ was about 30, 40, 50mm/minmm/min