Non-Debye and CPA Behaviors of Ionic Materials

1997 ◽  
Vol 500 ◽  
Author(s):  
J. C Wang
Keyword(s):  
Dielectric Loss ◽  
Complex Impedance ◽  
Thermal Fluctuations ◽  
Wide Frequency Range ◽  
Loss Peak ◽  
Warburg Impedance ◽  
Interfacial Processes ◽  
Wide Range ◽  
Ionic Materials ◽  
Hopping Models

ABSTRACTNon-Debye and constant-phase-angle (CPA) behaviors associated with the bulk and interfacial processes involving ionic materials are discussed in terms of complex impedance, admittance, and dielectric spectra. The yielding of a CPA and/or a broad non-Debye dielectric loss peak in a spectrum from fractal, pore, and ion-hopping models are compared and reviewed. The observed wide frequency ranges of the CPA behavior suggest that the fractal and pore models, which require a wide range of special structures down to very fine scales, may not be realistic. The ion-hopping model treats the bulk and interfacial processes as a chemical reaction having a thermally-activated Arrhenius form. Because of thermal fluctuations, the activation energies for ion hopping (e.g., in a potential double-well) have a double-exponential distribution which yields a non-Debye dielectric loss peak and a CPA spectrum over a wide frequency range above the loss peak. The distribution also has a special temperature dependence which may explain the invariance of dielectric spectral shapes with temperature, an observation by Joscher. The construction of CPA elements (in a generalized Warburg impedance form) using three distinct types of resistor-capacitor networks are presented and used to aid the discussion.

Solid State Sintering and Microstructural Evolution on Wide Frequency Range Dielectric Responses of Mechanically Activated CaTiO3 Ceramics

2015 ◽  
Vol 1107 ◽  
pp. 38-44
Author(s):  
Wong Yick Jeng ◽  
Hassan Jumiah ◽  
Mansor Hashim
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Sintering Temperature ◽  
Microstructural Analysis ◽  
High Energy ◽  
Wide Frequency Range ◽  
Milling Process ◽  
Frequency Range ◽  
Wide Range

The CaTiO3samples were prepared by high-energy ball milling process followed by sintering process from 1040 to 1200°C. X-ray diffraction (XRD), microstructural analysis, and dielectric properties over a wide range of frequency varying from 0.01 Hz to 1 GHz at room temperature were investigated. The formation of a single phase CaTiO3with orthorhombic structure was achieved at 1120°C and above. From a morphological point of view, sintering temperature promoted grain growth. Dielectric properties in the frequency range 0.01 Hz - 1 MHz revealed a relaxation-type process. Interfacial phenomena were the possible physical mechanisms that gave rise to these relaxation-type plots. Extending the frequencies above ~1 MHz yielded a frequency-independent characteristic of dielectric constant (ε'). These turned out to the relatively small dielectric loss (tan δ) values. The origin of the dielectric responses in the frequency range 1 MHz - 1 GHz was attributed to the domination of dipolar polarization. The grain size effect in sintered CaTiO3samples was prominent, notably in dielectric responses above ~1 MHz. Increase in sintering temperature remarkably led to an enhancement in dielectric constant values and reduction in dielectric loss values. Therefore, a significant correlation existed between microstructural features and dielectric properties.

Relaxation of Dielectric Loss Peak over Intermediate Temperature Range in Bi 5 TiNbWO 15 Intergrowth

2009 ◽  
Vol 26 (4) ◽  
pp. 047701 ◽  
Author(s):  
Wang Wei ◽  
Wang Xiao-Juan ◽  
Zhu Jun ◽  
Mao Xiang-Yu ◽  
Chen Xiao-Bing
Keyword(s):  
Dielectric Loss ◽  
Intermediate Temperature ◽  
Loss Peak ◽  
Temperature Range ◽  
Intermediate Temperature Range

Dielectric Loss in Vanadyl Pnictates

1990 ◽  
Vol 210 ◽  
Author(s):  
Joseph F. Lomax ◽  
John J. Fontanella ◽  
Mary C. Wintersgill ◽  
Anthony Kotarski
Keyword(s):  
Dielectric Loss ◽  
Complex Impedance ◽  
Audio Frequency ◽  
Vanadyl Phosphate ◽  
Nonstoichiometric Compound ◽  
Proton Movement ◽  
Related Compounds ◽  
Water Species ◽  
Acid Nature ◽  
Chemical Evidence

AbstractThe results of audio frequency complex impedance studies for vanadyl phosphate and its hydrates (VOPO4*nH2O;n=0,1,2) are reported. Measurements were made at seventeen frequencies between 10 and 105 Hz over the temperature range 5.5-380K. Two lowtemperature features were observed and are correlated with particular water species between the VOPO4 layers. In light of chemical evidence and compleximpedance measurements on related compounds, it is speculated that VOPCO4*nH2O (Pc = P, As) can be thought of as a mixed nonstoichiometric compound [VO(HPcO4)]x[VOPcO4O4]1-x*nH2O and the solid Brϕnsted acid nature of the compound is related to proton movement between layer pnictates and intralayer waters.

Polarization Dynamics in La5/3Sr1/3NiO4

1999 ◽  
Vol 602 ◽  
Author(s):  
N. Hakim ◽  
Z. Zhai ◽  
C. Kusko ◽  
P.V. Parimi ◽  
S-W. Cheong ◽  
...  
Keyword(s):  
Dielectric Loss ◽  
Dielectric Response ◽  
Charge Ordering ◽  
Dielectric Susceptibility ◽  
Dynamic Susceptibility ◽  
Loss Peak ◽  
Relaxation Rates ◽  
Relaxation Mode ◽  
Microwave Frequencies ◽  
Charge Stripe

AbstractDynamic susceptibility measurements at microwave frequencies (2 – 10GHz) are a sensitive probe of charge dynamcis in La5/3Sr1/3NiO4. Below the charge ordering temperature of 240K, a dielectric loss peak due to a relaxation mode with a large dielectric susceptibility is observed, and is associated with charge stripe formation. The dielectric response for Hω∥b (Eω ⊥ b) is well represented by ε(T) = εo/(1 – iωτ(T)), with εo, ∼ 50, and τ(T) = 2 × 10−9(sec) exp(−T/37K). Parallel conductivity σ(T) contributions dominate at higher temperatures and for Hω∥c (Eω ⊥ c). The dielectric loss peak observed indicates that the charge relaxation rates lie in the GHz frequency ranges.

Simulation of Dripping Using Dissipative Particle Dynamics

2010 ◽  
Author(s):  
Sorush Khajepor ◽  
Meysam Joulaian ◽  
Ahmadreza Pishevar ◽  
Yaser Afshar
Keyword(s):  
Dissipative Particle Dynamics ◽  
Thermal Fluctuations ◽  
Particle Dynamics ◽  
Fluid Density ◽  
Mesoscopic Simulation ◽  
Wall Boundary Condition ◽  
Wide Range ◽  
Breakup Time ◽  
Dpd Simulation ◽  
Good Agreement

Dissipative Particle Dynamics (DPD) is a mesoscopic simulation approach used in wide range of applications and length scales. In this paper, a DPD simulation is carried out to study dripping flow from a nozzle. The results of this study are used to answer this question that whether DPD is capable of simulating the free surface fluid on all different scales. A novel wall boundary condition is developed for the nozzle surface that controls its penetrability, near wall fluid density oscillations and the fluid slip close to the wall. We also utilize a new method to capture the real-time instantaneous geometry of the drop. The obtained results are in good agreement with the macroscopic experiment except near the breakup time, when the fluid thread that connects the primitive drop to the nozzle, becomes tenuous. At this point, the DPD simulation can be justified by thermal length of DPD fluid and the finest accuracy of the simulation that is the radius of a particle. We finally conclude that in spite of the fact that DPD can be used potentially for simulating flow on different scales, it is restricted to the nanoscale problems, due to the surface thermal fluctuations.

Frequency Dependence of Dielectric Parameters and A. C. Conductivity of Mg-Co-Zn Nanoferrites Synthesized via Combustion Method

2012 ◽  
Vol 584 ◽  
pp. 295-298 ◽  
Author(s):  
B.J. Madhu ◽  
M. Kavya ◽  
S. Razika Banu ◽  
B. Shruthi ◽  
C.P. Sowmya ◽  
...  
Keyword(s):  
Dielectric Loss ◽  
Combustion Method ◽  
Cobalt Nitrate ◽  
Zinc Nitrate ◽  
Magnesium Nitrate ◽  
X Ray Diffraction ◽  
Dielectric Parameters ◽  
X Ray ◽  
Wide Range ◽  
Hopping Model

Mg-Co-Zn nanoferrite particles were prepared by combustion method using stoichiometric compositions of magnesium nitrate, cobalt nitrate and zinc nitrate as oxidizers and urea as a fuel. The structure of the sample is studied with X-ray diffraction (XRD) using Cu-Kα radiation. The X-ray diffraction analysis revealed the nanocrystalline nature in the prepared ferrite samples. Dielectric and a. c. conductivity studies have been undertaken over a wide range of frequencies (100-5MHz) for Mg-Co-Zn nanoferrites at room temperature. The dielectric properties such as dielectric loss tangent (D), dielectric constant (ε′) and dielectric loss factor (ε″) were found to decrease with an increase in the frequency. Further, a. c. conductivity of the Mg-Co-Zn nanoferrite was found to increase with the increase in the frequency. The electrical conduction mechanism in the Mg-Co-Zn nanoferrite has been understood on the basis of the electron hopping model.

scholarly journals Modelling thermal fluctuations in non-ideal fluids with the lattice Boltzmann method

2011 ◽  
Vol 369 (1944) ◽  
pp. 2274-2282 ◽  
Author(s):  
M. Gross ◽  
R. Adhikari ◽  
M. E. Cates ◽  
F. Varnik
Keyword(s):  
Ideal Fluid ◽  
Lattice Boltzmann ◽  
Exact Result ◽  
Thermal Fluctuations ◽  
Ideal Gas ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Wide Range ◽  
Ideal Fluids ◽  
Boltzmann Method

Recently, we proposed a theoretical framework to include thermal fluctuations into the Lattice Boltzmann (LB) method for non-ideal fluids. Here, we apply a variant thereof to a certain class of force-based non-ideal fluid LB models. We find that ideal-gas-like noise is an exact result of the fluctuation–dissipation theorem in the hydrodynamic regime. It is shown that satisfactory equilibration of the density and fluid momentum can be obtained in a simulation over a wide range of length scales.

Dielectric Properties of Eucalyptus urophylla Under an Ultra-Wide Frequency Range

2020 ◽  
Vol 12 (8) ◽  
pp. 1236-1241
Author(s):  
He Xia ◽  
Wang Yong ◽  
Li Yunyan ◽  
Wei Yanqiang ◽  
Quan Peng ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Loss ◽  
Dielectric Permittivity ◽  
Loss Factor ◽  
Wide Frequency Range ◽  
Dielectric Loss Factor ◽  
Regression Equations ◽  
Eucalyptus Urophylla ◽  
Frequency Range ◽  
Tangential Directions

Dielectric properties of Eucalyptus urophylla wood were measured by using a network analyzer over an ultrawide frequency range between 0.2 GHz and 20 GHz. The effects of moisture content (MC), temperature and frequency on the dielectric permittivity and the dielectric loss factor of Eucalyptus urophylla were investigated along different grain directions. The results showed that the dielectric permittivity along with the dielectric loss factor increased significantly with the elevation in MC. At the frequency of 2380 MHz with the MC increasing from 0% to 100%, the dielectric permittivity along different grain directions (including longitudinal, radial and tangential directions) increased by 180%, 110% and 112%, respectively, while the loss factor along these three directions increased by 1642%, 3703% and 5058%, respectively. In addition, the increase in dielectric properties of Eucalyptus urophylla wood was determined with the temperature elevating. When the temperature elevated from 20 °C to 140 °C, the dielectric permittivity at 2380 MHz along the longitudinal, radial and tangential directions, increased by 19%, 14% and 15%, respectively, while the loss factor increased by 133% at most. As the radio frequency increased, the dielectric permittivity of wood decreased. Regression equations satisfactorily described the dielectric properties of wood along different grain directions with different moisture contents.

Structural, dielectric, electrical and piezoelectric properties of Ba4SrRTi3V7O30 (R=Sm, Dy) ceramics

Open Physics ◽  
2008 ◽  
Vol 6 (4) ◽  
Author(s):  
Priyadarshini Sahoo ◽  
Anuradha Panigrahi ◽  
Sunanda Patri ◽  
Ram Choudhary
Keyword(s):  
Room Temperature ◽  
Single Phase ◽  
Complex Impedance ◽  
Tungsten Bronze ◽  
Negative Temperature ◽  
Scanning Electron Micrographs ◽  
Polarization Study ◽  
Semiconducting Properties ◽  
Wide Range

AbstractPolycrystalline samples of Ba4SrRTi3V7O30 (R=Sm and Dy), members of the tungsten-bronze family, were prepared using a high-temperature, solid-state reaction technique and studied their electrical properties (using complex impedance spectroscopy) in a wide range of temperature (31–500°C) and frequency (1 kHz-1 MHz). Preliminary structural (XRD) analyses of these compounds show the formation of single-phase, orthorhombic structures at room temperature. The scanning electron micrographs (SEM) provided information on the quality of the samples and uniform distribution of grains over the entire surface of the samples. Detailed studies of the dielectric properties suggest that they have undergone ferroelectric-paraelectric phase transition well above the room temperatures (i.e., 432 and 355°C for R= Sm and Dy, respectively, at frequency 100 kHz). Measurements of electrical conductivity (ac and dc) as a function of temperature suggest that the compounds have semiconducting properties much above the room temperature, with negative temperature coefficient of resistance (NTCR) behavior. The existence of ferroelectricity in these compounds was confirmed from a polarization study.

Role of Light Quality and Temperature on Pitted Morningglory (Ipomoea lacunosa) Germination with After-Ripening

Weed Science ◽  
2007 ◽  
Vol 55 (2) ◽  
pp. 111-118 ◽  
Author(s):  
Jason K. Norsworthy ◽  
Marcos J. Oliveira
Keyword(s):  
Red Light ◽  
Thermal Fluctuations ◽  
Ipomoea Lacunosa ◽  
Direct Exposure ◽  
Wide Range ◽  
Thermal Amplitude ◽  
Pitted Morningglory ◽  
Buried Seed ◽  
Time Of Year ◽  
Response To Temperature

Pitted morningglory seed were collected in the fall of 2003 from Blackville, SC, and 2004 from Pendleton, SC, to assess the effect of After-Ripening and burial on light and temperature requirements for germination. Pitted morningglory germination was evaluated over a 12-mo period after maturation. Germination was neither stimulated by red light or inhibited by far-red light, nor was it reversible by red or far-red light. Light was not essential for germination of buried seed. Direct exposure to sunlight prevented germination of recently mature seed, but not once seed had sufficiently after-ripened. Pitted morningglory was capable of germination in darkness over a wide range of constant and fluctuating temperatures immediately after maturation. Germination in response to temperature varied with time of year after maturation, with the population from Pendleton having increased germination in May. Thermal fluctuations increased germination of both populations at suboptimal temperatures. Thermal amplitude regulation of germination varied over time and appeared to play a more important role in germination of after-ripened seed than recently mature ones. The ecological significance of changes in germination requirements with After-Ripening is discussed.

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