• Applied Science and Convergence Technology
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• 제24권6호
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• pp.224-227
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• 2015

Ferroelectric $Pb_2(Sc,Nb)O_6$ were prepared under two different sintering conditions using the oxide mixing method and the electrical properties were measured. The sintering conditions were $1350^{\circ}C$ for 25 minutes and $1400^{\circ}C$ for 20 minutes. EDX spectroscopy and XRD were used to determine the crystalline characteristic of the $Pb_2(Sc,Nb)O_6$ compositions Pyrochlore phase showed about 2% in all $Pb_2(Sc,Nb)O_6$ specimens. It expands the growth of crystals in samples sintered at $1400^{\circ}C$ than $1350^{\circ}C$, but all samples were the optimal crystallization. The temperature and frequency dependence of the complex dielectric constant and admittance were measured to analyze the electrical properties. The high dielectric constant of the specimens reflects the good stoichiometry and crystallization. The maximum value of the dielectric constant in the two specimens treated with sintering at $1350^{\circ}C$ and $1400^{\circ}C$ were more than 27,000, and the dielectric loss at room temperature is smaller than 0.05. The maximum dielectric constant decreased with increasing frequency, the transition temperature also increased in $Pb_2(Sc,Nb)O_6$ compositions. The admittance and susceptance values reach a peak at all temperatures, and the magnitude of the peak increases with increasing measuring temperature. Strong frequency dependent of maximum admittance, susceptance, dielectric constant and dielectric loss were observed.

• Journal of Electrical Engineering and Technology
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• 제9권3호
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• pp.978-983
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• 2014

The polymer nano composite possess good priority recently for engineering applications. Especially the electrical insulating materials attract the high performance of nano composites. In this work the ballmill synthesiation process of nano sized Alumina ($Al_2O_3$), the preparation of new nano composite material with an content of enamel and synthesized Alumina as 1wt%, 3wt% and 5wt%. Experimental investigation has been carried out for the prepared nano composites materials with respect to dielectric parameter measurements such as dielectric loss (tan ${\delta}$), dielectric constant (${\varepsilon}$), dielectric strength under various temperature. The partial discharge level also measured for all the samples and the PD inception voltage is also observed and compared. Weight loss of the material has been analyzed through TGA. It has been experimentally proved that 3wt% of Alumina nano filler added enamel has significant improvement in the dielectric and thermal properties.

• 한국세라믹학회지
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• 제19권4호
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• pp.281-286
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• 1982

The composition of glasses to be suitable for crystallisation of $BaTiO_3$ by heat-treatment and the dielectric properties of the glass-ceramics were investigated. The composition of the family of glasses was defined by the formula $\chi$ $BaTiO_3 + (100-$\chi$)Al_2O_3$.$2SiO_2$ and excess BaO. Data were presented on dielectric constant and loss tangent at various frequencies. The effects of excess BaO on dielectric properties were investigated. The additions of $Na_2O$ and $Nb_2O_5$ shifted the Curite temperature of these glass-ceramics. The glass composition which was able to be melted at 145$0^{\circ}C$ and moulded as homogeneous glass phase without devitrification should contain $Al_2O_3$.$2SiO_2$ more than 30 mole %. The more the amount of additive BaO increased, the more dielectric constant increased. When the maximum heat-treatment temperature was 105$0^{\circ}C$, we obtained higher dielectric constant than that of 95$0^{\circ}C$. The dielectric constant and the dielectric loss were stable at frequencies between 5$\times$104 and 107 cycle per second. When $Na_2O$ and $Nb_2O_5$ were added, the Curie temperature, presented at 14$0^{\circ}C$ to 15$0^{\circ}C$, shifted to lower temperature. Therefore, the glass-ceramics having high dielectric constant at room temperature were obtained.

• Applied Science and Convergence Technology
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• 제25권4호
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• pp.77-80
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• 2016

The $PbSc_{1/2}Nb_{1/2}O_3$ ceramics at a relatively low temperature of $1300^{\circ}C$ was successful synthesized. Solid state reaction of two-step process is not necessary. The dielectric constant, dielectric loss and admittance of ceramic samples were determined. The pyroelectric characteristics are in good agreement with the dielectric properties. Ferroelectric properties of well-formed the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics are in agreement with broad distribution of relaxation phenomenon. Relatively strong frequency dependent of dielectric constant is observed at about $110^{\circ}C$. The distinct thermal hysteresis was observed in the measurement of the dielectric constant and dielectric loss. The critical exponents of during cooling and heating measurements in the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics were 1.14 and 1.59 at 1 kHz, respectively.

• 전기학회논문지
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• 제57권1호
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• pp.73-77
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• 2008

We have investigated dielectric polarization in organic light-emitting diodes using 8-hydroxyquinoline aluminum($Alq_3$) as an electron transport and emissive material. We analyzed the dielectric polarization of organic light-emitting diodes using characteristics of impedance and equivalent circuit of $ITO/Alq_3/Al$. Impedance characteristics was measured complex impedance Z and phase ${\theta}$ in the frequency range of $1{\times}40Hz\;to\;1{\times}10^8Hz$. We obtained complex electrical conductivity, dielectric constant, and loss tangent(tan${\delta}$) of the device at room temperature. And, we obtained the equivalent circuit of $ITO/Alq_3/Al$ through analyzing dielectric constant and dielectric loss tangent. From these analyses, we could interpret a conduction mechanism and dielectric polarization.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권11호
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• pp.603-608
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• 2000

$(Ba, Sr)TiO_{3}$[BST] thin films were fabricated on the Pt/TiO$_2$/SiO$_2$/Si substrate by the RF sputtering. The structure and dielectric properties of the BST thin films with the substrate temperature were investigated. Increasing the substrate temperature, The BST phase increased and barium multi titanate phases decreased. Increasing the frequency, the dielectric constant decreased and the dielectric loss increased. The dielectric constant and dielectric loss of the BST thin films deposited at 50$0^{\circ}C$ were 300 and 0.018, respectively at 1 kHz. The leakage current density of the BST thin films deposited at 50$0^{\circ}C$ was $10^{-9}$ A/$\textrm{cm}^2$ with applied voltage of 3V. Because of the high dielectric constant(300), low dielectric loss(0.018) and low leakage current($10^{-9}$ A/$\textrm{cm}^2$), BST thin films deposited at 50$0^{\circ}C$ is expecting for the application of DRAM.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 추계학술대회 논문집
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• pp.90-90
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• 2009

The $Sr_{0.7}Bi_{2.3}Nb_2O_9$(SBN) thin films are deposited on Pt-coated electrode($Pt/Ti.SiO_2/Si$) using RF sputtering method. The dielectric constant of SBN thin films were increased with the increase of annealing temperature. The maximum dielectric constant of SBN thin film is obtained by annealing at 700[$^{\circ}C$]. The dielectric constant and dielectric loss had a stable value within -5~+5[V].

• 한국전기전자재료학회논문지
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• 제11권11호
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• pp.1007-1013
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• 1998

In this paper, the dielectric properties of fabricated Polyvinylidene fluoride(PVDF, $PVF_2$) thin film with substrate temperature from 30 to at vapor deposition. The dielectric properties of PVDF thin film had been studied in the frequency range from 10Hz to 4MHz at measuring temperature between 20 and $100^{/circ}C$. The anomalous increasing in dielectric constant and dielectric loss at low frequencies and high temperature was described for PVDF thin film containing ion impurities. In particularly, ion mobility of fabricated PVDF thin film at substrate temperature at $30^{/circ}C$ decrease from $2\times10^{-5}\;to\;3.07$\times10^{-7}cm^2/V.s$ On the other hand, ion density increase abruptly from 1.49\times$$10^{13}$ to $1.5\times$10^{16}$cm^{-3}$ In spite of decreasing of ion mobility, dielectric constants and dielectric loss for PVDF thin film increase rapidly with decreasing frequency and high temperature. It was concluded that the dielectric constants and dielectric loss was related to ion density than to ion mobility at low frequency and high temperatures.

• Transactions on Electrical and Electronic Materials
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• 제10권2호
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• pp.49-52
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• 2009

Barium strontium calcium titanate powders were prepared with the sol-gel method. Ferroelectric $(Ba_{0.54}Sr_{0.36}Ca_{0.1})TiO_3$(BSCT) thick films were fabricated by the screen-printing method on alumina substrate. Then we investigated the structural and dielectric properties of the BSCT thick films at different sintering temperatures. The thermal analysis showed that the BSCT polycrystalline perovskite phase formed at around $660^{\circ}C$. The X-ray diffraction analysis showed a cubic perovskite structure with no second phase present in all of the BSCT thick films. The average grain size and the thickness of the specimens sintered at $1450^{\circ}C$ were about $1.6{\mu}m$ and $45{\mu}m$, respectively. The relative dielectric constant increased and the dielectric loss decreased as the sintering temperature was increased; for BSCT thick films sintered at $1450^{\circ}C$ the values of the dielectric constant and the dielectric loss were 5641 and 0.4%, respectively, at 1 kHz.

• Journal of Biosystems Engineering
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• 제24권2호
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• pp.123-134
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• 1999

The electrical properties such as dielectric constant, dielectric loss factor and AC conductivity of grain were presented to measure the moisture content of grain using RF impedance. At frequency ranging from 1 to 10MHz and room temperature, $20^{\circ}C$, vector network analyzer(HP4195) and coaxial type sample holder were used to analyze the electrical properties of paddy(11∼24%w.b.), brown rice(11∼18%w.b.), barley(11∼21%w.b.) and wheat(11∼23%w.b.) depending on the moisture content, frequency and bulk density. The dielectric constant and AC conductivity of grain samples increased with moisture content and bulk density. The dielectric constants decreased with frequency and could be expressed as function of the moisture density(decimal moisture $content{\times}bulk$ density).