The Metallic State of Conducting Polymers: Microwave Dielectric Response and Optical Conductivity

1993 ◽  
Vol 328 ◽  
Author(s):  
A. J. Epstein ◽  
J. Joo ◽  
R. S. Kohlman ◽  
A. G. Macdiarmid ◽  
J. M. Weisinger ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Conducting Polymers ◽  
Three Dimensional ◽  
Microwave Frequency ◽  
Linear Increase ◽  
Metallic State ◽  
Microwave Dielectric ◽  
Conducting Polyaniline ◽  
New Generation ◽  
Domain Length

ABSTRACTRecent advances in processing of polyaniline and polyacetylene have resulted in a new generation of conducting polymers with higher dc conductivities. We present the temperature (T) dependent microwave frequency dielectric constant, dc conductivity, and Kramers-Kronig analysis of conducting polyaniline and polyacetylene. The low temperature dielectric constant, ε, increases with the square of the x-ray crystalline domain length for preparations of HCl protonated polyaniline. For the highest crystalline polyaniline samples, ε increases dramatically with increasing T, supporting formation of three-dimensional (3-D) coupled “mesoscopic” Metallic regions. A “metallic” negative ε is observed for d,1-camphor sulfonie acid doped polyaniline prepared in m-cresol. Optical studies show a linear increase in reflectivity below 7000 cm-1. Below 600 cm-1 the reflectance increases rapidly. Kramers-Kronig analysis of the ir-visible results are presented. Highly conducting polyaniline is shown to have two plasma frequencies, one at ∼ 1.1 eV involving all the conduction band electrons, and one at ∼0.015 eV (120 cm-1) that is suggested to arise from the most delocalized electrons. The concept of inhomogeneous disorder is introduced. The results for polyaniline are compared to those of highly doped polyacetylene which also show metallic negative ε demonstrating the intrinsic metallic nature of the new generation of conducting polymers.

Microwave dielectric properties of RETiTaO6 (RE = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) ceramics

2002 ◽  
Vol 17 (10) ◽  
pp. 2561-2566 ◽  
Author(s):  
Kuzhichalil Peethambaran Surendran ◽  
Sam Solomon ◽  
Manoj Raama Varma ◽  
Pezholil Mohanan ◽  
Mailadil Thomas Sebastian
Keyword(s):  
Dielectric Constant ◽  
Ionic Radius ◽  
Microwave Dielectric Properties ◽  
Microwave Frequency ◽  
Rare Earth Ions ◽  
Ionic Radii ◽  
Low Dielectric ◽  
Microwave Dielectric ◽  
State Ceramic ◽  
High Dielectric

Microwave dielectric ceramics based on RETiTaO6 (RE = La, Cc, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Y, Er, Yb, Al, and In) were prepared using a conventional solid-state ceramic route. The structure and microstructure of the samples were analyzed using x-ray diffraction and scanning electron microscopy techniques. The sintered samples were characterized in the microwave frequency region. The ceramics based on Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy, which crystallize in orthorhombic aeschynite structure, had a relatively high dielectric constant and positive τf while those based on Ho, Er, and Yb, with orthorhombic euxenite structure, had a low dielectric constant and negative τf. The RETiTaO6 ceramics had a high-quality factor. The dielectric constant and unit cell volume of the ceramics increased with an increase in ionic radius of the rare-earth ions, but density decreased with it. The value of τf increased with an increase in RE ionic radii, and a change in the sign of τf occurred when the ionic radius was between 0.90 and 0.92 Å. The results indicated that the boundary of the aeschynite to euxenite morphotropic phase change lay between DyTiTaO6 and HoTiTaO6. Low-loss ceramics like ErTiTaO6 (εr = 20.6, Quxf = 85,500), EuTiTaO6 (r = 41.3, Quxf = 59,500), and YtiTaO6 (εr = 22.1, Quxf = 51,400) are potential candidates for dielectric resonator applications.

scholarly journals Dielectric Behavior of Low Microwave Loss Unit Cell for All Dielectric Metamaterial

2015 ◽  
Vol 2015 ◽  
pp. 1-6 ◽  
Author(s):  
Tianhuan Luo ◽  
Bo Li ◽  
Qian Zhao ◽  
Ji Zhou
Keyword(s):  
Dielectric Constant ◽  
Microwave Frequency ◽  
Calcium Titanate ◽  
Dielectric Behavior ◽  
Unit Cell ◽  
Solid State Method ◽  
Microwave Dielectric ◽  
Unit Cells ◽  
Microwave Permittivity ◽  
Lower Loss

With a deep study of the metamaterial, its unit cells have been widely extended from metals to dielectrics. The dielectric based unit cells attract much attention because of the advantage of easy preparation, tunability, and higher frequency response, and so forth. Using the conventional solid state method, we prepared a kind of incipient ferroelectrics (calcium titanate, CaTiO3) with higher microwave permittivity and lower loss, which can be successfully used to construct metamaterials. The temperature and frequency dependence of dielectric constant are also measured under different sintering temperatures. The dielectric spectra showed a slight permittivity decrease with the increase of temperature and exhibited a loss of 0.0005, combined with a higher microwave dielectric constant of ~167 and quality factorQof 2049. Therefore, CaTiO3is a kind of versatile and potential metamaterial unit cell. The permittivity of CaTiO3at higher microwave frequency was also examined in the rectangular waveguide and we got the permittivity of 165, creating a new method to test permittivity at higher microwave frequency.

Pavement Damage Due to Conventional and New Generation of Wide-Base Super Single Tires

2005 ◽  
Vol 33 (4) ◽  
pp. 210-226 ◽  
Author(s):  
I. L. Al-Qadi ◽  
M. A. Elseifi ◽  
P. J. Yoo ◽  
I. Janajreh
Keyword(s):  
Carrying Capacity ◽  
Material Properties ◽  
Three Dimensional ◽  
Fe Analysis ◽  
Load Carrying Capacity ◽  
Inflation Pressure ◽  
3D Finite Element ◽  
Load Carrying ◽  
Pavement Damage ◽  
New Generation

Abstract The objective of this study was to quantify pavement damage due to a conventional (385/65R22.5) and a new generation of wide-base (445/50R22.5) tires using three-dimensional (3D) finite element (FE) analysis. The investigated new generation of wide-base tires has wider treads and greater load-carrying capacity than the conventional wide-base tire. In addition, the contact patch is less sensitive to loading and is especially designed to operate at 690kPa inflation pressure at 121km/hr speed for full load of 151kN tandem axle. The developed FE models simulated the tread sizes and applicable contact pressure for each tread and utilized laboratory-measured pavement material properties. In addition, the models were calibrated and properly validated using field-measured stresses and strains. Comparison was established between the two wide-base tire types and the dual-tire assembly. Results indicated that the 445/50R22.5 wide-base tire would cause more fatigue damage, approximately the same rutting damage and less surface-initiated top-down cracking than the conventional dual-tire assembly. On the other hand, the conventional 385/65R22.5 wide-base tire, which was introduced more than two decades ago, caused the most damage.

Microstructure and Microwave Dielectric Properties of BaTi4O9 Ceramics Derived from a Sol-Gel Precursor

2011 ◽  
Vol 326 ◽  
pp. 127-130
Author(s):  
Xian Li Huang ◽  
Fu Ping Wang ◽  
Ying Song
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sol Gel ◽  
Microwave Dielectric Properties ◽  
Sintering Process ◽  
Temperature Coefficients ◽  
Microwave Dielectric ◽  
Ceramic Samples ◽  
Quality Factor Q

In the present work, the microstructure and microwave dielectric properties of BaTi4O9 ceramics derived from a sol-gel precursor were presented. Density measuring results demonstrated that the largest densities of ceramic sample about 96.7% could be reached by virtue of a cool iso-static press and a sintering process at at 1300 °C for 6 hours. The dielectric constant (εr), quality factor (Q×f) and the temperature coefficients (τf) of the BaTi4O9 ceramic samples were 36.65, 28000 GHz, +20.2 ppm/°C, respectively. XRD, SEM and XPS were used to characterize the microstructure of the ceramics samples. Substantial Ti3+ was proposed to be the cause of dielectric loss.

Effect of Sintering Behavior on Microwave Properties of (Ca0.8Sr0.2)ZrO3 Ceramics for Resonators

2014 ◽  
Vol 787 ◽  
pp. 338-341
Author(s):  
Cheng Hsing Hsu ◽  
Chia Hao Chang ◽  
Wen Shiush Chen ◽  
Jenn Sen Lin ◽  
Chun Hung Lai
Keyword(s):  
Dielectric Constant ◽  
Sintering Temperature ◽  
Microwave Dielectric Properties ◽  
Sintering Behavior ◽  
Passive Components ◽  
Suitable Candidate ◽  
Solid State Route ◽  
Microwave Dielectric ◽  
Microwave Ceramic ◽  
Conventional Solid State Route

Microwave dielectric properties and microstructures of (Ca0.8Sr0.2)ZrO3 ceramics prepared by the conventional solid-state route have been studied. The values of the dielectric constant (εr) were 22-26. The Q×f values of 10400–11500 GHz were obtained when the sintering temperatures were in the range of 1400–1490°C. The temperature coefficient of the resonant frequency τf was not sensitive to the sintering temperature. The εr value of 26, the Q×f value of 11500 GHz, and the τf value of-9 ppm/°C were obtained for (Ca0.8Sr0.2)ZrO3 ceramics sintering at 1490°C. The ceramic, (Ca0.8Sr0.2)ZrO3 is proposed as a suitable candidate material for application in highly selective microwave ceramic passive components.

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