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Title: Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique

Abstract

The distribution of relaxation times approach, a less frequently employed dielectric data analysis technique, is utilized to better understand the relaxation characteristics of composites consisting of metal-coated, hollow glass spheres dispersed in a paraffin wax matrix. The dielectric properties of the composite samples are measured by means of impedance spectroscopy in the frequency range 0.1 mHz to 10 MHz. The application of a mixture law is not appropriate for the analysis of the frequency-dependent properties of the considered system on this broad frequency range. However, utilization of the distribution of relaxation times procedure to study the dielectric behaviour shows clear trends in the mixtures' relaxation spectra. Relaxation processes of the paraffin wax and those specific to the composites are found from the extracted distribution of relaxation times spectra. The influence of the filler concentration, q, on the dielectric properties is examined; a relaxation with a narrow distribution at intermediate frequencies becomes broad with the addition of the filler. This relaxation, in the form of the low-frequency-dispersions (also known as constant phase angle) phenomenon, dominates the dielectric properties of the composites with high bead concentration, q>0.15. The variation in dielectric properties of individual samples whose bead concentrations q are nominally themore » same is discussed in terms of possible microstructural variations.« less

Authors:
 [1];  [2];  [3];  [4]
  1. ORNL
  2. Center for Nondestructive Evaluation, Ames, Iowa
  3. DSTL, Porton Down, Salisbury, Wiltshire, UK
  4. QinetiQ Ltd, Hampshire, UK
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
OE USDOE - Office of Electric Transmission and Distribution
OSTI Identifier:
1003676
DOE Contract Number:
DE-AC05-00OR22725
Resource Type:
Journal Article
Resource Relation:
Journal Name: Philosophical Magazine; Journal Volume: 86; Journal Issue: 16
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; DATA ANALYSIS; DIELECTRIC MATERIALS; DIELECTRIC PROPERTIES; DISTRIBUTION; FILLERS; FREQUENCY RANGE; GLASS; IMPEDANCE; MIXTURES; PARAFFIN; RELAXATION; RELAXATION TIME; SPECTRA; SPECTROSCOPY

Citation Formats

Tuncer, Enis, Bowler, Nicola, Youngs, I. J., and Lymer, K. P. Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique. United States: N. p., 2006. Web. doi:10.1080/14786430500527361.
Tuncer, Enis, Bowler, Nicola, Youngs, I. J., & Lymer, K. P. Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique. United States. doi:10.1080/14786430500527361.
Tuncer, Enis, Bowler, Nicola, Youngs, I. J., and Lymer, K. P. Sun . "Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique". United States. doi:10.1080/14786430500527361.
@article{osti_1003676,
title = {Investigating low-frequency dielectric properties of a composite using the distribution of relaxation times technique},
author = {Tuncer, Enis and Bowler, Nicola and Youngs, I. J. and Lymer, K. P.},
abstractNote = {The distribution of relaxation times approach, a less frequently employed dielectric data analysis technique, is utilized to better understand the relaxation characteristics of composites consisting of metal-coated, hollow glass spheres dispersed in a paraffin wax matrix. The dielectric properties of the composite samples are measured by means of impedance spectroscopy in the frequency range 0.1 mHz to 10 MHz. The application of a mixture law is not appropriate for the analysis of the frequency-dependent properties of the considered system on this broad frequency range. However, utilization of the distribution of relaxation times procedure to study the dielectric behaviour shows clear trends in the mixtures' relaxation spectra. Relaxation processes of the paraffin wax and those specific to the composites are found from the extracted distribution of relaxation times spectra. The influence of the filler concentration, q, on the dielectric properties is examined; a relaxation with a narrow distribution at intermediate frequencies becomes broad with the addition of the filler. This relaxation, in the form of the low-frequency-dispersions (also known as constant phase angle) phenomenon, dominates the dielectric properties of the composites with high bead concentration, q>0.15. The variation in dielectric properties of individual samples whose bead concentrations q are nominally the same is discussed in terms of possible microstructural variations.},
doi = {10.1080/14786430500527361},
journal = {Philosophical Magazine},
number = 16,
volume = 86,
place = {United States},
year = {Sun Jan 01 00:00:00 EST 2006},
month = {Sun Jan 01 00:00:00 EST 2006}
}
  • The distribution of relaxation times approach, a less frequently employed dielectric data analysis technique, is utilized to better understand the relaxation characteristics of composites consisting of metal-coated, hollow glass spheres dispersed in a paraffin wax matrix. The dielectric properties of the composite samples are measured by means of impedance spectroscopy in the frequency range 0.1mHz to 10 MHz. The application of a mixture law is not appropriate for the analysis of the frequency-dependent properties of the considered system on this broad frequency range. However, utilization of the distribution of relaxation times procedure to study the dielectric behaviour shows clear trendsmore » in the mixtures' relaxation spectra. Relaxation processes of the paraffin wax and those specific to the composites are found from the extracted distribution of relaxation times spectra. The influence of the filler concentration, q, on the dielectric properties is examined; a relaxation with a narrow distribution at intermediate frequencies becomes broad with the addition of the filler. This relaxation, in the form of the low-frequency-dispersions (also known as constant phase angle) phenomenon, dominates the dielectric properties of the composites with high bead concentration, q > 0:15. The variation in dielectric properties of individual samples whose bead concentrations q are nominally the same is discussed in terms of possible microstructural variations.« less
  • Dielectric spectroscopy is carried out for intrinsic and aluminum-doped TiO{sub 2} rutile films which are deposited on RuO{sub 2} by the atomic layer deposition technique. Capacitance and conductance are measured in the 0.1 Hz–100 kHz range, for ac electric fields up to 1 MV{sub rms}/cm. Intrinsic films have a much lower dielectric constant than rutile crystals. This is ascribed to the presence of oxygen vacancies which depress polarizability. When Al is substituted for Ti, the dielectric constant further decreases. By considering Al-induced modification of polarizability, a theoretical relationship between the dielectric constant and the Al concentration is proposed. Al doping drastically decreasesmore » the loss in the very low frequency part of the spectrum. However, Al doping has almost no effect on the loss at high frequencies. The effect of Al doping on loss is discussed through models of hopping transport implying intrinsic oxygen vacancies and Al related centers. When increasing the ac electric field in the MV{sub rms}/cm range, strong voltage non-linearities are evidenced in undoped films. The conductance increases exponentially with the ac field and the capacitance displays negative values (inductive behavior). Hopping barrier lowering is proposed to explain high-field effects. Finally, it is shown that Al doping strongly improves the high-field dielectric behavior.« less
  • Ba{sub 0.5}Sr{sub 0.5}TiO{sub 3}-Mg{sub 2}TiO{sub 4} composite ceramics are fabricated via the conventional solid-state reaction method. The microstructures, dielectric tunability, and microwave properties of composite ceramics are investigated. The dielectric constant is tailored from 335 to 35 by manipulating the addition of Mg{sub 2}TiO{sub 4} from 50% to 80% weight ratio and the tunability is 10.8% measured at 10 kHz for the 80% Mg{sub 2}TiO{sub 4} addition. The composite ceramics with high Q value (>200) at L band are useful for potential tunable microwave device applications in the wireless communication system.
  • A detailed structural study of the {ital c}(2{times}2)Cl/Cu(001) adsorbate system was made, using the angle-resolved photoemission extended-fine-structure (ARPEFS) technique at low temperature, which yields both more accurate surface structural information and near-surface structural information for deeper substrate layers. Electrons were detected along two emission directions, (001) and (011), and at two temperatures, 110 and 300 K. The Cl atoms were found to adsorb in the fourfold hollow site, 1.604(5) A above the first copper layer, with a Cl-Cu bond length of 2.416(3) A (in which the errors in parentheses are statistical standard deviations only). These values are in excellent agreementmore » with a previous low-energy electron-diffraction study by Jona {ital et} {ital al}. The {ital c}(2{times}2)Cl-covered first copper layer showed no relaxation with respect to the bulk position. However, a small corrugation of the second copper layer was found: The second-layer copper atoms below the Cl atoms move 0.042(12) A away from the surface, while those in open positions remain in their bulk positions. The distances from the Cl atoms to the third and fourth copper layers were found to be 5.222(25) and 7.023(22) A, respectively, yielding a bulklike interlayer spacing. Thus the depth sensitivity of the low-temperature ARPEFS facilitated definitive referencing of near-surface atomic positions to the underlying lattice.« less
  • The disordered structures and low temperature dielectric relaxation properties of Bi{sub 1.667}Mg{sub 0.70}Nb{sub 1.52}O{sub 7} (BMN) and Bi{sub 1.67}Ni{sub 0.75}Nb{sub 1.50}O{sub 7} (BNN) misplaced-displacive cubic pyrochlores found in the Bi{sub 2}O{sub 3}-M{sup II}O-Nb{sub 2}O{sub 5} (M=Mg, Ni) systems are reported. As for other recently reported Bi-pyrochlores, the metal ion vacancies are found to be confined to the pyrochlore A site. The B{sub 2}O{sub 6} octahedral sub-structure is found to be fully occupied and well-ordered. Considerable displacive disorder, however, is found associated with the O'A{sub 2} tetrahedral sub-structure in both cases. The A-site ions were displaced from Wyckoff position 16d (1/2more » , 1/2 , 1/2 ) to 96 h (1/2 , 1/2 -{epsilon}{sub A}, 1/2 +{epsilon}{sub A}) while the O' oxygen was shifted from position 8b (3/8 , 3/8 , 3/8 ) to Wyckoff position 32e (3/8 +{epsilon}{sub o}{sup '}, 3/8 +{epsilon}{sub o}{sup '}, 3/8 +{epsilon}{sub o}{sup '}). The refined displacement magnitudes off the 16d and 8b sites for the A and O' sites were 0.408 A/0.423 A and 0.350 A/0.369 A for BMN/BNN, respectively. - Graphical abstract: The final displacively disordered average structure of Bi{sub 1.667}Mg{sub 0.70}Nb{sub 1.52}O{sub 7} (BMN) projected along a close to <110> direction.« less