Low frequency divergence of the dielectric constant and signature of the Meyer–Neldel rule in the ac conductivity of PbS and PbS:Mn nanorods in polymer

2008 ◽  
Vol 103 (6) ◽  
pp. 064311 ◽  
Author(s):  
A. R. Mandal ◽  
L. Kabir ◽  
S. K. Mandal
Keyword(s):  
Dielectric Constant ◽  
Ac Conductivity ◽  
Low Frequency

Dielectric Properties of Polyester Reinforced with Carbon Black Particles

2011 ◽  
Vol 110-116 ◽  
pp. 170-176
Author(s):  
Omed Ghareb Abdullah ◽  
Dana Abdull Tahir ◽  
Gelas Mukaram Jamal ◽  
Salah Raza Saeed
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Carbon Black ◽  
Low Temperatures ◽  
Ac Conductivity ◽  
Low Frequency ◽  
Frequency Range ◽  
Exponential Factor ◽  
Increasing Temperature ◽  
Dielectric Permittivity And Loss

Dielectric constant and ac conductivity of Polyester doped with carbon black are investigated in the frequency range (0.5-103) KHz and within the temperature range (26-80) oC. Dielectric permittivity and loss tangent reduced with increasing frequency and increase with increasing temperature. The ac conductivity σac for all samples were found to be weak frequency dependent at low frequency, however vary with frequency as a power law ωs at higher frequency range. The variation of frequency exponential factor s between 0.63 and 0.77, indicates a dominant hopping process at low temperatures. From the temperature dependence of dc conductivity, the increase of activation energy was observed with carbon black concentrations.

Dielectric and structural properties of iron- and sodium-fumarates

2012 ◽  
Vol 36 (1) ◽  
pp. 21-29 ◽  
Author(s):  
Sonja Skuban ◽  
Tanja Džomié ◽  
Agneš Kapor ◽  
Željka Cvejić ◽  
Srđan Rakic
Keyword(s):  
Dielectric Constant ◽  
Ionic Conductivity ◽  
Structural Properties ◽  
Ac Conductivity ◽  
Loss Factor ◽  
Low Frequency ◽  
Relative Dielectric Constant ◽  
Frequency Range ◽  
Dielectric Parameters ◽  
Increasing Temperature

Abstract The behaviour of dielectric parameters such as the relative dielectric constant (ε''), the relative loss factor (ε'') and the ac conductivity of well known pharmaceutical materials Fe(II)-fumarate and Na-fumarate were studied as a function of temperature (in the range from 303K to 483 K) and frequency (in the range from 0.1 Hz to 100 kHz). The values of the conductivity are in the range of 10−5 Ω−1m−1 to 10−9 Ω−1m−1 for Fe(II)-fumarate and 10−6 Ω−1m−1 to 10−11 Ω−1m−1 for Na-fumarate. The conductivity of both materials increases with the increase in temperature and frequency. It was found that both ε' and ε'' decrease with increasing frequency and increase with increasing temperature for both materials. The highest changes are in the low frequency range. The obtained values of the dielectric parameters and conductivity suggest that these materials are dielectric with similar structure, most probably polymeric, with the mechanism of ionic conductivity.

scholarly journals The effects of additive on microstructure and electrical properties of batio3 ceramics

2004 ◽  
Vol 1 (3) ◽  
pp. 89-98 ◽  
Author(s):  
Vesna Paunovic ◽  
Ljiljana Zivkovic ◽  
Ljubomir Vracar ◽  
Vojislav Mitic ◽  
Miroslav Miljkovic
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Low Frequency ◽  
Dissipation Factor ◽  
The Other ◽  
Uniform Microstructure ◽  
Average Grain Size ◽  
Solid State Sintering ◽  
Curie Temperatures

In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2?m and 3-5?m respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

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.

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