The anisotropy of ac conductivity and dielectric constant of anisotropic conductor–insulator composites

2010 ◽  
Vol 45 (11) ◽  
pp. 2843-2851 ◽  
Author(s):  
Yuichi Hazama ◽  
Jun Nakamura ◽  
Akiko Natori
Keyword(s):  
Dielectric Constant ◽  
Ac Conductivity

scholarly journals Preparation, Structural, Electrical, and Ferroelectric Properties of Lead Niobate–Lead Zirconate–Lead Titanate Ternary System

2015 ◽  
Vol 2015 ◽  
pp. 1-12 ◽  
Author(s):  
Rashmi Gupta ◽  
Seema Verma ◽  
Vishal Singh ◽  
K. K. Bamzai
Keyword(s):  
Dielectric Constant ◽  
Ternary System ◽  
Lead Titanate ◽  
Ac Conductivity ◽  
Perovskite Phase ◽  
Ferroelectric Properties ◽  
Ternary Systems ◽  
Lead Zirconate ◽  
X Ray ◽  
Dispersive Nature

A ternary system of lead niobate–lead zirconate–lead titanate with composition xPN–yPZ–(x-y)PT where x=0.5 and y=0.15, 0.25, and 0.35 known as PNZT has been prepared by conventional mixed oxide route at a temperature of 1100°C. The formation of the perovskite phase was established by X-ray diffraction analysis. The surface morphology studied by scanning electron microscopy shows the formation of fairly dense grains and elemental composition was confirmed by energy dispersive X-ray analysis. Dielectric properties like dielectric constant and dielectric loss (ε′ and tan⁡δ) indicate poly-dispersive nature of the material. The temperature dependent dielectric constant (ε′) curve indicates relaxor behaviour with two dielectric anomalies. The poly-dispersive nature of the material was analysed by Cole-Cole plots. The activation energy follows the Arrhenius law and is found to decrease with increasing frequency for each composition. The frequency dependence of ac conductivity follows the universal power law. The ac conductivity analysis suggests that hopping of charge carriers among the localized sites is responsible for electrical conduction. The ferroelectric studies reveal that these ternary systems are soft ferroelectric.

scholarly journals Synthesis and Characterization of CaxSryBa1-x-yFe12-zLazO19 by Standard Ceramic Method

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Rohit K. Mahadule ◽  
Purushottam R. Arjunwadkar ◽  
Megha P. Mahabole
Keyword(s):  
Dielectric Constant ◽  
Ac Conductivity ◽  
Phenomenological Theory ◽  
Dielectric Polarization ◽  
Ceramic Method ◽  
Chemical Phase ◽  
Ferrite Structure ◽  
Magnetic Dilution ◽  
Chemical Phase Analysis

The polycrystalline compounds with chemical formula CaxSryBa1-x-yFe12-zLazO19 (CSBFLO) were synthesized via standard ceramic method. The chemical phase analysis was carried out by X-ray powder diffraction (XRD) method, which confirmed the formation of the magnetoplumbite phase belonging to ferrite structure. The frequency dependence of AC conductivity and dielectric constant was studied in the frequency range of 10 Hz to 2 MHz. The experimental results revealed that AC conductivity increases with increasing frequency, which is in agreement with Koop’s phenomenological theory. However, variation in dielectric constant required explanation in light of dielectric polarization. Magnetic characterization included studies of parameters such as Ms, Mr, Hc, and Tc, and results were explained via magnetic dilution and canting spin structure.

Electrical Performance of Cofired Alumina Substrates at High Temperatures

2013 ◽  
Vol 10 (3) ◽  
pp. 89-94 ◽  
Author(s):  
Liang-Yu Chen
Keyword(s):  
Dielectric Constant ◽  
High Temperature ◽  
Ac Conductivity ◽  
Large Scale ◽  
Dissipation Factor ◽  
Electrical Performance ◽  
Prototype System ◽  
Polycrystalline Aluminum ◽  
Polycrystalline Alumina ◽  
Dielectric Performance

A 96% polycrystalline alumina (Al2O3) based prototype packaging system with Au thick-film metallization successfully facilitated long term testing of high temperature SiC electronic devices for over 10,000 h at 500°C previously. However, the 96% Al2O3 chip-level packages of this prototype system were not fabricated via a commercial cofire process, which would be more suitable for large scale commercial production. The cofired alumina materials adopted by the packaging industry today usually contain several percent of glass constituents to allow cofiring processes at temperatures usually lower than the regular sintering temperature for alumina. In order to answer the question of whether cofired alumina substrates can provide a reasonable high temperature electrical performance comparable to regular 96% alumina sintered at 1700°C, this paper reports on the dielectric performance of a selected high temperature cofired ceramic (HTCC) alumina substrate and a low temperature cofired ceramic (LTCC) alumina (polycrystalline aluminum oxides with glass constituents) substrate from room temperature to 550°C at frequencies of 120 Hz, 1 KHz, 10 KHz, 100 KHz, and 1 MHz. Parallel-plate capacitive devices with dielectrics of these cofired alumina and precious metal electrodes were used for measurement of the dielectric properties of the cofired alumina materials in the temperature and frequency ranges. The capacitance and AC parallel conductance of these capacitive devices were directly measured by an AC impedance meter, and the dielectric constant and parallel AC conductivity of the dielectric were calculated from the capacitance and conductance measurement results. The temperature and frequency dependent dielectric constant, AC conductivity, and dissipation factor of selected LTCC and HTCC cofired alumina substrates are presented and compared with those of 96% alumina. Metallization schemes for cofired alumina for high temperature applications are discussed to address the packaging needs for low-power 500°C SiC electronics.

Dielectric and ac Conductivity Studies on Nanocrystalline Mn Modified Cobalt Ferrite

2018 ◽  
Vol 24 (8) ◽  
pp. 5629-5632 ◽  
Author(s):  
Sweety Supriya ◽  
Sunil Kumar ◽  
Manoranjan Kar
Keyword(s):  
Dielectric Constant ◽  
Frequency Response ◽  
Electrical Transport ◽  
Ac Conductivity ◽  
Cobalt Ferrite ◽  
Electrical Transport Properties ◽  
Arrhenius Behavior ◽  
Temperature Dependent ◽  
Two Layer Model ◽  
Frequency Temperature

The ac conductivity and dielectric properties on CoFe2−xMnxO4 for x = 0.00, 0.10, 0.15 and 0.20 have been studied in detail. All the samples were prepared in nanocrystalline size. These materials are found to be crystallized to Fd <mml:math display="block"> <mml:semantics> <mml:mover accent="true"> <mml:mi>3</mml:mi> <mml:mo>¯</mml:mo> </mml:mover> </mml:semantics> </mml:math> m space group in cubic spinel structure. The dielectric constant and ac conductivity has been discussed as a function of frequency, temperature and composition. The relation between dielectric constant and ac conductivity has been analyzed and the results validate each other. The frequency response of ac conductivity (σac) obeys Johnschers power law and the parameters obtained, explain the sources of ac and dc electrical conductivity in the material. The frequency response of σac follows Maxwell–Wagner two-layer model. The influence of frequency as pumping force on activation energy has been determined. The temperature dependent ac conductivity shows the Arrhenius behavior. The σac observed to be enhanced with increase in frequency as well as temperature. The semiconducting behavior (NTCR) was also evident from temperature dependent electrical transport properties study. The low value of ac conductivity suggests a possible use of this material in dielectric applications.

Dielectric constant and ac conductivity in polyaniline derivatives

1996 ◽  
Vol 97 (12) ◽  
pp. 1029-1031 ◽  
Author(s):  
N.J. Pinto ◽  
P.D. Shah ◽  
P.K. Kahol ◽  
B.J. McCormick
Keyword(s):  
Dielectric Constant ◽  
Ac Conductivity
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