scholarly journals Evidence of a third kind of Johnscher’s like universal dielectric response

2018 ◽  
Vol 08 (04) ◽  
pp. 1850028 ◽  
Author(s):  
Maheswar Panda
Keyword(s):  
Dielectric Constant ◽  
Dielectric Response ◽  
Entire Range ◽  
Polyvinylidene Fluoride ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Process Conditions ◽  
Dipolar Relaxation ◽  
Polymer Metal ◽  
The Difference

Polymer/metal composites (PMC) comprising of polyvinylidene fluoride/nanocrystalline nickel with varying volume fractions of nickel ([Formula: see text]) prepared under cold press show an insulator to metal transition (IMT) at percolation threshold ([Formula: see text]). The two kinds of generalized Johnscher’s universal dielectric response (UDR) laws on both sides of IMT hold good, while for the percolative sample, none of the two laws hold good. Neither the concept of dipolar relaxation nor anomalous low frequency dispersion stands valid for [Formula: see text], while a completely different, neutral and competing electrical behavior is observed over the entire range of frequencies. The emerged third kind of Johnscher’s like UDR for [Formula: see text] is observed and the relaxation law has been formulated as the ratio of imaginary and real parts of dielectric constant remains constant over the entire range of frequency starting from dc to any higher frequency. The value of the constant is attributed to depend on the PMC, the dielectric constant of the polymer, the differences of conductivity and fractions of the components of the PMC and also on their connectivity arising due to the difference of their process conditions. The emerged unique dielectric relaxation consists of multiple relaxations arising due to the combination of other relaxations (arising due to the two different types of species) present in the sample, [Formula: see text]. This novel material may be suitable for certain specific applications in electrical and electronics engineering.

scholarly journals Dielectric spectroscopy of polymer-metal composites across the percolation threshold

2014 ◽  
Vol 04 (04) ◽  
pp. 1450027 ◽  
Author(s):  
Maheswar Panda ◽  
V. Srinivas ◽  
A. K. Thakur
Keyword(s):  
Percolation Threshold ◽  
Volume Fraction ◽  
Strong Dependence ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Process Conditions ◽  
Predominant Role ◽  
Dipolar Relaxation ◽  
Metal Composites ◽  
Polymer Metal

Polymer (polar/nonpolar)/metal composites (PMC) were prepared under different process conditions. In polar PMC, dipolar relaxation plays a predominant role below percolation threshold (fc) and anomalous low frequency dispersion (ALFD) becomes dominant above fc while ALFD is the only likely possibility for nonpolar PMC above fc. The magnitude of relaxation exponents "m", "p" and "n", evaluated from the experimental results using Jonscher's universal dielectric response (JUDR) laws, falls within the universal limit ~ [0, 1] with additional feature of strong dependence on volume fraction of conductor (f con ). The decrease in the relaxation exponent "m" with an increase of f con is directly linked with decrease in the number of dipoles of the polymer in the composite and is accompanied by a distribution of relaxation time due to increased heterogeneity of the system. The magnitude of the relaxation exponent "n" decreases at fc, due to the prevalence of Maxwell–Wagner–Sillar polarization contributed by uncorrelated electrons.

Dielectric Response of Structured Multilayered Polyvinylidene Fluoride Films

2013 ◽  
Vol 721 ◽  
pp. 121-124
Author(s):  
Long Jiang ◽  
Qiong Fu ◽  
Wei Ping Li
Keyword(s):  
Dielectric Constant ◽  
Theoretical Model ◽  
Dielectric Property ◽  
Spin Coating ◽  
Dielectric Response ◽  
Polyvinylidene Fluoride ◽  
High Energy ◽  
Multilayer Films ◽  
Material Structure ◽  
Number Of Layers

To make clear the effect of thickness and layer number on the dielectric property of poly (vinylidenedi fluoride) (PVDF), the different multilayer films were prepared by spin coating. The relation between them has been explained by both experimental results and theoretical model. It is found the dielectric constant of multilayer increase linearly with the number of layers but decrease with the thickness. It is helpful to optimize the material structure and size parameters of polymer films for high energy capacitors.

Influence of Iodine on Low Frequency Dielectric Properties of Anthrone

1995 ◽  
Vol 60 (11) ◽  
pp. 1809-1814
Author(s):  
Grzegorz W. Bak ◽  
Marian Kryszewski
Keyword(s):  
Charge Transfer ◽  
Dielectric Properties ◽  
Dielectric Response ◽  
Charge Transfer Complex ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Low Loss ◽  
Remarkable Change ◽  
Ct Complex

Low frequency dielectric properties of polycrystalline anthrone and anthrone/iodine charge-transfer complex are presented. Polycrystalline anthrone proves to be a typical low-loss material. Iodization of anthrone pellets leads to a remarkable change in dielectric properties. Dielectric response of anthrone/iodine CT complex shows comparatively strong low frequency dispersion. The change in dielectric properties proves to be reversible to great extend as removing of iodine by heating at 373 K for a few hours almost completely restores the dielectric values of a virgin anthrone sample.

scholarly journals Frequency-dependent scaling behavior of polyvinylidene fluoride/metal composites

2019 ◽  
Vol 09 (02) ◽  
pp. 1950010
Author(s):  
Maheswar Panda
Keyword(s):  
Polyvinylidene Fluoride ◽  
Dielectric Constants ◽  
Scaling Behavior ◽  
Process Conditions ◽  
Polarization Model ◽  
Metal Composites ◽  
Frequency Dependent ◽  
Alloy Particles ◽  
Polymer Metal ◽  
Experimental Values

The frequency-dependent percolation and scaling behavior of a variety of polymer/metal composites (PMC), based on polyvinylidene fluoride (PVDF) matrix and various types of fillers such as; metal/alloy particles of different sizes, prepared through cold/hot pressing process conditions have undergone investigation. The universal percolation behavior in the vicinity of percolation threshold ([Formula: see text]), i.e., [Formula: see text] and [Formula: see text] is well satisfied, which suggests [Formula: see text] to be independent of frequency, where [Formula: see text] and [Formula: see text] are the effective ac conductivity and effective dielectric constants of the composite and [Formula: see text] is the frequency of applied ac signal. The obtained experimental values of the exponents are consistent with the inter-cluster polarization model ([Formula: see text] and [Formula: see text]), satisfying [Formula: see text]. The widely used percolative equations are well fitted with the experimental results of all PMC at all values of the frequency. The value of [Formula: see text] is found to be independent of frequency of the applied signal, suggesting the studied PMC are real percolating systems. The critical exponents ([Formula: see text] and [Formula: see text]) which characterize the divergence of [Formula: see text] and [Formula: see text] in the vicinity of [Formula: see text] are found to decrease with the increase of frequency. The rate of decrease of ‘[Formula: see text]’ and ‘[Formula: see text]’ with increase of frequency is attributed to the method of preparation, size of the fillers, adhesiveness of polymer/filler and the rate of decrease of [Formula: see text] with frequency (due to the absence of different extents of contributions of various types of conventional polarizations).

Dielectric and impedance spectroscopy of K+-doped MgAl2O4 nanoparticles

2018 ◽  
Vol 32 (15) ◽  
pp. 1850189
Author(s):  
Javed Ahmad ◽  
S. H. Bukhari ◽  
M. Qadeer Awan ◽  
M. Ehsan Mazhar ◽  
A. R. Makhdoom
Keyword(s):  
Dielectric Constant ◽  
Impedance Spectroscopy ◽  
High Frequency ◽  
Dielectric Response ◽  
Room Temperature ◽  
Parent Compound ◽  
Low Frequency ◽  
Space Charge Polarization ◽  
Relaxation Phenomena ◽  
Frequency Range

In this study, the dielectric response of Potassium (K[Formula: see text])-doped magnesium aluminates nanoparticles (Mg[Formula: see text]K[Formula: see text]Al2O4, x = 0.0, 0.25, 0.5, 0.75, 1.0) have been investigated as a function of frequency (20 Hz to 2 MHz) at room-temperature. Interestingly, the behavior of dielectric constant indicated the ionic or space charge polarization in the low-frequency range and it remains almost constant at high frequency. However, the value of conductivity increases at higher frequencies which is consistent with the previously reported results for the parent compound MgAl2O4. Moreover, the Cole–Cole plots represent various relaxation phenomena reflecting the existence of grain (boundaries) resistance effects.

scholarly journals Crystal Structure, Raman Spectroscopy and Dielectric Properties of New Semiorganic Crystals Based on 2-Methylbenzimidazole

Crystals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 573
Author(s):  
E. V. Balashova ◽  
F. B. Svinarev ◽  
A. A. Zolotarev ◽  
A. A. Levin ◽  
P. N. Brunkov ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Dielectric Constant ◽  
Dielectric Properties ◽  
Water Solution ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Xrd Analysis ◽  
Strong Increase ◽  
Chemical Compositions ◽  
X Ray Diffraction

New single crystals, based on 2-methylbenzimidazole (MBI), of MBI-phosphite (C16H24N4O7P2), MBI-phosphate-1 (C16H24N4O9P2), and MBI-phosphate-2 (C8H16N2O9P2) were obtained by slow evaporation method from a mixture of alcohol solution of MBI crystals and water solution of phosphorous or phosphoric acids. Crystal structures and chemical compositions were determined by single crystal X-ray diffraction (XRD) analysis and confirmed by XRD of powders and elemental analysis. Raman spectroscopy of new crystals evidences the presence in crystals of MBI-, H3PO3-, or H3PO4- and water molecules. Dielectric properties of crystals reveal strong increase and low frequency dispersion of dielectric constant and losses at heating, indicating the appearance of proton conductivity. At low temperatures in MBI-phosphate-2, an increase of dielectric constant analogous to quantum paraelectric state is observed.

scholarly journals Magnetic, Thermal and Electrical Transport Properties of o-Substituted Polyanilines Encapsulated with Fe2O3 Nanoparticles

2019 ◽  
Vol 32 (2) ◽  
pp. 265-270
Author(s):  
R. Suganthi ◽  
S. Padmaja ◽  
S. Jhancy Mary
Keyword(s):  
Dielectric Constant ◽  
Electrical Transport ◽  
Oxidative Polymerization ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Decomposition Temperature ◽  
Spectroscopic Techniques ◽  
Electrical Transport Properties ◽  
Frequency Independent

Poly(2-nitroaniline), poly(2-nitroaniline)-Fe2O3 and poly(2-methylaniline)-Fe2O3 nanocomposites synthesized by in situ chemical oxidative polymerization technique were characterized by XRD, thermal (TGA and DTA) and FTIR & UV-visible spectroscopic techniques. The thermal stability was confirmed by the integral procedural decomposition temperature (IPDT) and oxidation index (OI) calculations. The electrical conductivity and dielectric properties were also investigated. At low frequency region, the dielectric constant decreases with increase in frequency due to electrical relaxation process. At high frequencies, dielectric constant is independent of frequency. At low frequency, there was strong frequency dispersion of permittivity and above 3 Hz, a frequency independent behaviour in permittivity was observed. The materials exhibit ferromagnetic behaviour.

scholarly journals Synthesis and characterization of strontium-doped barium titanate thin film by dip and dry technique

2021 ◽  
pp. 2150002
Author(s):  
S. G. Chavan ◽  
A. N. Tarale ◽  
D. J. Salunkhe
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Dielectric Constant ◽  
Dielectric Loss ◽  
Complex Impedance ◽  
Low Frequency ◽  
Frequency Dispersion ◽  
Dip Coating ◽  
Morphological Properties ◽  
Constant Frequency

Thin films of polycrystalline (Ba[Formula: see text]Sr[Formula: see text]TiO3 ([Formula: see text] = 0.2 and 0.3) with Perovskite structure were prepared by a dip and dry technique on a platinum-coated silicon substrate. The good quality thin films with uniform microstructure and thickness were successfully produced by dip-coating techniques annealed at 730[Formula: see text]C for 1 h. The resulting thin film shows a well-developed dense polycrystalline structure with more uniform grain size distribution. The BST thin films were characterized for their structural, Raman spectroscopy, morphological properties, and complex impedance properties. The dielectric constant-frequency curve showed the good dielectric constant and loss dielectric loss with low-frequency dispersion. The BST 0.3 thin film reveals that the dielectric constant and dielectric loss at a frequency of 1 kHz were 578 and 0.02, respectively. The obtained results on dielectric properties can be analyzed in terms of the Maxwell–Wagner model.

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