ChemInform Abstract: DIELECTRIC BEHAVIOR OF MIXED LITHIUM-NICKEL FERRITES AT LOW FREQUENCIES

1983 ◽  
Vol 14 (1) ◽  
Author(s):  
P. V. REDDY ◽  
T. S. RAO
Keyword(s):  
Dielectric Behavior ◽  
Low Frequencies

ON THE DIELECTRIC BEHAVIOR OF LiCo3/5Fe2/5VO4 CERAMICS

2010 ◽  
Vol 24 (07) ◽  
pp. 665-670
Author(s):  
MOTI RAM
Keyword(s):  
Activation Energy ◽  
Dielectric Constant ◽  
Frequency Dependence ◽  
Chemical Method ◽  
Arrhenius Plot ◽  
Dielectric Behavior ◽  
Tangent Loss ◽  
Low Frequencies ◽  
Different Temperatures ◽  
Tan Δ

The LiCo 3/5 Fe 2/5 VO 4 ceramics has been fabricated by solution-based chemical method. Frequency dependence of the dielectric constant (εr) at different temperatures exhibits a dispersive behavior at low frequencies. Temperature dependence of εr at different frequencies indicates the dielectric anomalies in εr at Tc (transition temperature) = 190°C, 223°C, 263°C and 283°C with (εr) max ~ 5370, 1976, 690 and 429 for 1, 10, 50 and 100 kHz, respectively. Frequency dependence of tangent loss ( tan δ) at different temperatures indicates the presence of dielectric relaxation in the material. The value of activation energy estimated from the Arrhenius plot of log (τd) with 103/T is ~(0.396 ± 0.012) eV.

scholarly journals Dielectric Behavior and Morphostructural Characteristics of Some HDPE Composites / Metal Nanopowders

2019 ◽  
Vol 56 (1) ◽  
pp. 103-109 ◽  
Author(s):  
Alina-Ruxandra Caramitu ◽  
Sorina Mitrea ◽  
Virgil Marinescu ◽  
George-Andrei Ursan ◽  
Mihaela Aradoaie ◽  
...  
Keyword(s):  
Dielectric Spectroscopy ◽  
High Surface ◽  
High Surface Area ◽  
Dielectric Behavior ◽  
Sem Images ◽  
Low Frequencies ◽  
High Frequencies ◽  
Metal Filler ◽  
Powder Filler ◽  
Composite Samples

HDPE composite samples with aluminum and iron nanopowders were made by extrusion and injection. Samples of material obtained were characterized by comparative determinations of dielectric spectroscopy and SEM microscopy. SEM images have indicated that the agglomerations of the powders used are persistent, do not decompose during extrusion and injection processing. Determinations by dielectric spectroscopy indicated that HDPE composite materials with metal nanopowder filler have higher dielectric losses than pure HDPE (reference). The highest increases in tgd up to 2.6 times, were recorded for 50 nm nanopowders with specific high surface area (over 20 m2 / g). The electrical conductivity of the investigated samples increases with increasing frequency, both for pure HDPE and for HDPE with metal powder filler. As a result of the film effect in the HDPE case with metal filler, the increases in the high frequencies range are lower than in the extremely low frequencies range.

On the Nonlinear Dielectric Behavior of Desoxyribonucleic Acid Fibers at Low Frequencies

1965 ◽  
Vol 43 (10) ◽  
pp. 3603-3608 ◽  
Author(s):  
C. Brot ◽  
B. Lassier ◽  
A. H. Sharbaugh ◽  
S. I. Reynolds ◽  
D. M. White
Keyword(s):  
Dielectric Behavior ◽  
Desoxyribonucleic Acid ◽  
Low Frequencies ◽  
Nonlinear Dielectric

Mathematical and deep learning analysis based on tissue dielectric properties at low frequencies predict outcome in human breast cancer

2021 ◽  
pp. 1-13
Author(s):  
Mamdouh M. Shawki ◽  
Mohamed Moustafa Azmy ◽  
Mohammed Salama ◽  
Sanaa Shawki
Keyword(s):  
Breast Cancer ◽  
Deep Learning ◽  
Human Breast Cancer ◽  
Threshold Value ◽  
Dielectric Behavior ◽  
Support Vector ◽  
Human Breast ◽  
Great Chance ◽  
Low Frequencies ◽  
Learning Analysis

BACKGROUND: The early detection of human breast cancer represents a great chance of survival. Malignant tissues have more water content and higher electrolytes concentration while they have lower fat content than the normal. These cancer biochemical characters provide malignant tissue with high electric permittivity (ε´) and conductivity (σ). OBJECTIVE: To examine if the dielectric behavior of normal and malignant tissues at low frequencies (α dispersion) will lead to the threshold (separating) line between them and find the threshold values of capacitance and resistance. These data are used as input for deep learning neural networks, and the outcomes are normal or malignant. METHODS: ε´ and σ in the range of 50 Hz to 100 KHz for 15 human malignant tissues and their corresponding normal ones have been measured. The separating line equation between the two classes is found by mathematical calculations and verified via support vector machine (SVM). Normal range and the threshold value of both normal capacitance and resistance are calculated. RESULTS: Deep learning analysis has an accuracy of 91.7%, 85.7% sensitivity, and 100% specificity for instant and automatic prediction of the type of breast tissue, either normal or malignant. CONCLUSIONS: These data can be used in both cancer diagnosis and prognosis follow-up.

Investigation of dielectric behavior of the PVC/BaTiO3 composite in low-frequencies

2018 ◽  
Vol 32 (09) ◽  
pp. 1850110 ◽  
Author(s):  
A. Berrag ◽  
S. Belkhiat ◽  
L. Madani
Keyword(s):  
Dielectric Properties ◽  
Dielectric Behavior ◽  
Index Formula ◽  
Response Analysis ◽  
Frequency Response Analysis ◽  
Frequency Range ◽  
Low Frequencies ◽  
X Ray ◽  
Space Charges ◽  
Loss Index

Polyvinyl chloride (PVC) is widely used as insulator in electrical engineering especially as cable insulation sheaths. In order to improve the dielectric properties, polymers are mixed with ceramics. In this paper, PVC composites with different weight percentages 2 wt.%, 5 wt.%, 8 wt.% and 10 wt.% were prepared and investigated. Loss index ([Formula: see text]) and dielectric constant ([Formula: see text]) have been measured using an impedance analyzer RLC. Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) equipped with energy dispersive X-ray (EDX) have been used as characterization techniques. The incorporation of BaTiO3 does not modify the crystallinity and the morphology of the PVC but reduces the space charges, therefore the dielectric losses. The frequency response analysis has been followed in the frequency ranges (20–140 Hz and 115–1 MHz). Relaxation frequencies have been evaluated in each frequency range. Experimental measurements have been validated using Cole–Cole’s model. Experimental results show well that BaTiO3 as a filler improves the dielectric properties of PVC.

Magnetoelectric properties of BST/LSMO particulate composites

2011 ◽  
Vol 1368 ◽  
Author(s):  
Juan Beltran-Huarac ◽  
R. Martinez ◽  
R. Palai
Keyword(s):  
Magnetic Fields ◽  
Composite Structures ◽  
Colossal Magnetoresistance ◽  
Relative Dielectric Constant ◽  
Dielectric Behavior ◽  
Dielectric Measurement ◽  
Particulate Composites ◽  
Low Frequencies ◽  
X Ray ◽  
Low Dielectric

ABSTRACTCurrently, ferroelectric and ferromagnetic particulate composites are receiving a great deal of interest due to their novel applications in microelectronic devices. Their excellent properties such as high relative dielectric constant, low dielectric loss, strong tunability, and ferromagnetism with colossal magnetoresistance can be controlled by manipulating both electric and magnetic fields. Ba0.7Sr0.3TiO3 /La0.67Sr0.33MnO3 (BST/LSMO) composite was prepared with 20:1 wt% by a high temperature solid-state reaction route. The X-ray diffraction (XRD) pattern confirmed the formation and the coexistence of both phases corresponding to BST and LSMO. High resolution field emission scanning electron microscope (FE-SEM) and energy dispersive X-ray spectroscopy (EDS) revealed a uniform distribution of the grain size throughout the surface of the sample and the presence of all the constituent elements with its esteemed reaction stoichiometry, respectively. In spite of the presence of both phases, only one transition peak was seen (50Hz-5MHz) around 295 K in dielectric measurement suggesting a nonlinear magnetoelectric coupling. The dielectric properties of BST/LSMO composite carried with different magnetic fields (0-1.7 T) show significant change in the BST dielectric behavior at low frequencies. The M-H curves at room temperature (RT) showed a drop in the saturation magnetization compared with pure LSMO is consistent with our composite structures.

Preparation and Characterization of Dielectric Behavior of A2/3Cu3Ti4O12 (A = Nd, Sm, Gd, Dy) Ceramics

2010 ◽  
Vol 67 ◽  
pp. 28-33 ◽  
Author(s):  
Dorota Szwagierczak ◽  
Jan Kulawik
Keyword(s):  
Single Phase ◽  
Elevated Temperatures ◽  
Relaxation Times ◽  
Dielectric Behavior ◽  
X Ray Diffraction ◽  
Conventional Solid State Reaction ◽  
Low Frequencies ◽  
Perovskite Materials ◽  
Very High

In this work perovskite materials A2/3Cu3Ti4O12 (where A=Nd, Sm, Gd, Dy) were synthesized by conventional solid state reaction and sintered at 1000-1100°C. X-ray diffraction analysis confirmed single-phase composition of the investigated ceramics. Dielectric properties of the samples were investigated in the temperature range from -55 to 300°C at frequencies 10 Hz – 2 MHz. Dielectric permittivities of the ceramics are very high, exceeding 105 at low frequencies and/or elevated temperatures (above 50°C) and 103 at higher frequencies and/or low temperatures. Two observed contributions to the dielectric response are attributed to semiconducting grains and more resistive grain boundaries. For Nd2/3Cu3Ti4O12 and Sm2/3Cu3Ti4O12 ceramics, the observed low- and high frequency plateaus are lower than those for Gd2/3Cu3Ti4O12 and Dy2/3Cu3Ti4O12. The relaxation times determined on the basis of impedance data were found to decrease with increasing atomic number of lanthanide. The analysis of the impedance spectroscopic data and the microstructure implies spontaneous formation of internal barrier layer capacitors in the investigated materials.

Kε AND TAN δ SPECTRA OF DRY LUNAR ANALOG MEASURED BY VARIOUS TECHNIQUES

Geophysics ◽  
1973 ◽  
Vol 38 (1) ◽  
pp. 125-134
Author(s):  
Jisoo Ryu ◽  
S. H. Ward ◽  
W. P. Nash ◽  
D. Buzzell
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Rock Sample ◽  
Mineralogical Composition ◽  
Dielectric Behavior ◽  
High Dispersion ◽  
Debye Relaxation ◽  
Low Frequencies

For a two‐terminal measurement on a rock sample in a dry state whose dielectric loss tangent is less than unity, contact substitution without the insertion of any material between the electrode plates and the sample should be used to yield accurate measurements. The insertion may disturb measurements on the dielectric properties of the dry rock sample. A proposed optimum technique is useful when rock samples are not free of moisture and helps overcome electrode effects. Due to similarities in mineralogical composition and dielectric behavior, Duluth hornfels can serve as a terrestrial analog to some lunar basalts. The dielectric constant spectra of the Duluth hornfels measured during various stages in preparing a sample indicate that high dispersion at low frequencies is attributed mainly to the moisture content of the sample. Its intrinsic dielectric constant was found to be about 13, while its dielectric loss tangent linearly decreases from 0.07 at 100 hz to 0.019 at 100 khz in a log‐log plot. No Debye relaxation process was observed on the Duluth hornfels sample at room temperature over the frequency range used.

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