• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.20 no.6
• /
• pp.249-253
• /
• 2010

After the specimen of A-site defect perovskite $La_{1/3}NbO_3$ single crystal was manufactured, the dielectric properties were studied between the temperature range of 10 and 800 K. The dielectric anomaly appeared at 50 K and 650 K, and, at about 650 K, the thermal hysteresis of dielectric constant was shown. The ac-conductivity of bulk showed the lowest activation energy of 0.43 eV at 560~690 K. Based on the results, it is assumed that the dielectric anomaly at 50K and 650 K was due to the antiparallel shift of $Nb^{5+}$-ion and the rearrangement of $Nb^{3+}$-ion, respectively.

• Journal of the Korean Ceramic Society
• /
• v.43 no.2 s.285
• /
• pp.131-135
• /
• 2006

In this study, the dielectric, magnetic and transport properties of $Gd_{0.33}Sr_{0.67}FeO_3$ have been analyzed. The dielectric loss anomaly was found to be around 170 K. The activation energy corresponding to relaxation process of this dielectric anomaly was 0.17 eV. From the temperature dependence of the characteristic frequency, we concluded that the elementary process of the dielectric relaxation peak observed is correlated with polaron hopping between $Fe^{3+}\;and\;Fe^{4+}$ ions. The electrical resistivity displayed thermally activated temperature dependence above 200 K with an activation energy of 0.16 eV. In addition, the temperature dependence of thermoelectric power and resistivity suggests that the charge carrier responsible for conduction is strongly localized.

• Journal of Surface Science and Engineering
• /
• v.33 no.4
• /
• pp.217-221
• /
• 2000

The gate oxide thickness is becoming thinner and thinner in order to speed up the semiconductor CMOS devices. We have investigated very thin$ SiO_2$ gate oxide layers and found anomaly between the thickness determined with capacitance measurement and these obtained with cross-sectional high resolution transmission electron microscopy. The thicknesses difference of the two becomes important for the thickness of the oxide below 5nm. We propose that the variation of dielectric constant in thin oxide films cause the anomaly. We modeled the behavior as (equation omitted) and determined $\varepsilon_{bulk}$=3.9 and $\varepsilon_{int}$=-4.0. We predict that optimum $SiO_2$ gate oxide thickness may be $20\AA$ due to negative contribution of the interface dielectric constant. These new results have very important implication for designing the CMOS devices.s.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.30 no.6
• /
• pp.215-219
• /
• 2020

After the specimen of A-site defect double Perovskite La1/3TaO3 single crystal was manufactured, the dielectric properties have been studied between the temperature range of 10 and 800 K. Under 500 K, a paraelectric behavior has been shown, and above 550 K, a dielectric anomaly and a thermal history of dielectric constant has been shown. An activation energy by measurement of ac-conductivity has been the largest with 1.83 eV in the areas below 560 K, 0.35 eV in the areas of 560~690 K, and 0.28 eV in the areas of high temperature above 690 K. From these results, it is assumed that in the areas below 500 K, La3+-ion and vacancy-site are arranged in disorder to maintain a paraelectric phase. And in the areas near 560 K with the highest activation energy, a dielectric anomaly is attributes to rearrangement of La3+-ion due to conduction to vacancy-site or jumping.

• The Journal of Natural Sciences
• /
• v.8 no.1
• /
• pp.17-22
• /
• 1995

Dielectric constant was measured near the consolute point of a binary mixture of water and Poly[bis(methoxyethoxyethoxy)phosphazene], MEEP. Dielectric constant changed incontinously at phase separation temperature plotted against the concentration to abtain coexistence curve. The critical temperatures and the critical concentration were $71^{\circ}C$, 5.5% as determined from the coexistence curve, respectivley. The critical exponent of dielectric constant, $\theta$, was 0.85. The dependence of dielectric constant on frequency is discussed in this report.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2002.10a
• /
• pp.86.1-86
• /
• 2002

• Geophysics and Geophysical Exploration
• /
• v.5 no.4
• /
• pp.280-290
• /
• 2002

Three-dimensional (3-D) electromagnetic (EM) modeling algorithm has been developed using finite element method (FEM) to acquire more efficient interpretation techniques of EM data. When FEM based on nodal elements is applied to EM problem, spurious solutions, so called 'vector parasite', are occurred due to the discontinuity of normal electric fields and may lead the completely erroneous results. Among the methods curing the spurious problem, this study adopts vector element of which basis function has the amplitude and direction. To reduce computational cost and required core memory, complex bi-conjugate gradient (CBCG) method is applied to solving complex symmetric matrix of FEM and point Jacobi method is used to accelerate convergence rate. To verify the developed 3-D EM modeling algorithm, its electric and magnetic field for a layered-earth model are compared with those of layered-earth solution. As we expected, the vector based FEM developed in this study does not cause ny vector parasite problem, while conventional nodal based FEM causes lots of errors due to the discontinuity of field variables. For testing the applicability to high frequencies 100 MHz is used as an operating frequency for the layer structure. Modeled fields calculated from developed code are also well matched with the layered-earth ones for a model with dielectric anomaly as well as conductive anomaly. In a vertical electric dipole source case, however, the discontinuity of field variables causes the conventional nodal based FEM to include a lot of errors due to the vector parasite. Even for the case, the vector based FEM gave almost the same results as the layered-earth solution. The magnetic fields induced by a dielectric anomaly at high frequencies show unique behaviors different from those by a conductive anomaly. Since our 3-D EM modeling code can reflect the effect from a dielectric anomaly as well as a conductive anomaly, it may be a groundwork not only to apply high frequency EM method to the field survey but also to analyze the fold data obtained by high frequency EM method.

• Proceedings of the Korean Ceranic Society Conference
• /
• 2000.10a
• /
• pp.153.2-153
• /
• 2000

• Proceedings of the Materials Research Society of Korea Conference
• /
• 2000.11a
• /
• pp.41-41
• /
• 2000

• Journal of Advanced Navigation Technology
• /
• v.16 no.4
• /
• pp.635-640
• /
• 2012

In this paper, The TE (Transverse Electric) scattering problems by a perfectly conducting strip grating over a grounded two dielectric layers are analyzed by applying the conductive boundary condition and the FGMM (Fourier-Galerkin Moment Method) known as a numerical procedure, then the induced surface current density is expanded in a series of the multiplication of the unknown coefficient and the exponential function as a simple function. Generally, the reflected power gets increased according as the relative permittivity ${\epsilon}_{r2}$ and the thickness of dielectric layer $t_2$ of the region-2 in the presented structure gets increased, respectively. The sharp variations of the reflected power are due to resonance effects were previously called wood's anomaly, the numerical results show in good agreement with those of the existing papers.