scholarly journals Диэлектрическая спектроскопия и механизм фазового перехода полупроводник-металл в легированных пленках VO-=SUB=-2-=/SUB=-:Ge и VO-=SUB=-2-=/SUB=-:Mg

2020 ◽  
Vol 54 (4) ◽  
pp. 331
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
М.Э. Пашкевич ◽  
Е.Б. Шадрин
Keyword(s):  
Vanadium Dioxide ◽  
Room Temperature ◽  
Dissipation Factor ◽  
Electrical Circuit ◽  
Low Frequencies ◽  
High Frequencies ◽  
Cole Diagram ◽  
Metal Phase Transition ◽  
Additional Maximum ◽  
Frequency Dependences

Abstract The frequency dependences of the dissipation factor tanδ( f ) and the Cole–Cole diagrams for germanium- and magnesium-doped vanadium-dioxide films in the range of 0.1–10^6 Hz are obtained. Measurements at temperatures between 173–373 K are performed. It is found that, at room temperature, an additional maximum in the tanδ( f ) dependence and an additional semicircle in the Cole–Cole diagram of the VO_2:Ge films as compared with those of undoped films appear at low frequencies. In the VO_2:Mg films, similar additional features in the dielectric spectra are observed at high frequencies. It is shown that the shape of the Cole – Cole diagrams for all the films is almost temperature independent in the mentioned temperature range, while the frequencies f _0 corresponding to the tanδ( f ) maxima increase with temperature. To interpret the dielectric spectroscopy data, a combined equivalent electrical circuit of the film sample is proposed. The mechanisms of the effect of Ge and Mg impurities on the characteristics of the complex Mott–Peierls semiconductor–metal phase transition are established.

scholarly journals Диэлектрическая спектроскопия и особенности механизма фазового перехода полупроводник-металл в пленках VO-=SUB=-2-=/SUB=-

2020 ◽  
Vol 54 (2) ◽  
pp. 153
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
М.Э. Пашкевич ◽  
Е.Б. Шадрин
Keyword(s):  
Phase Transition ◽  
Electrical Properties ◽  
Vanadium Dioxide ◽  
Thermal Hysteresis ◽  
Hysteresis Loops ◽  
Electrical Circuit ◽  
Equivalent Electrical Circuit ◽  
Transition Mechanism ◽  
Metal Phase Transition ◽  
Frequency Dependences

Abstract In the range of 0.1–10^6 Hz, the temperature-induced transformation of the frequency dependences of the dielectric-loss tangent tanδ( f ) as well as the Cole–Cole diagrams for undoped vanadium-dioxide films are investigated. The measurements are carried out in the temperature range T = 273–373 K. It is shown that the shape of the Cole–Cole diagrams for all films depends slightly on the temperature in the specified interval, while the frequencies f _0 corresponding to the peaks of the function tanδ( f ) increase with temperature. The thermal-hysteresis loops of the frequency positions f _0( T ) of the peaks are measured. When interpreting the data of dielectric spectroscopy, a complex equivalent electrical circuit of the sample is used; it makes it possible to detect the presence of two types of grains with different electrical properties in undoped VO_2 films. The presence of two types of grains determines the features of the semiconductor–metal phase-transition mechanism in VO_2 films.

scholarly journals Фазовый переход полупроводник--суперионик в пленках сульфида серебра

2020 ◽  
Vol 62 (12) ◽  
pp. 2138
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
М.Э. Пашкевич ◽  
И.О. Попова ◽  
Е.Б. Шадрин
Keyword(s):  
Experimental Data ◽  
Thin Films ◽  
Phase Transition ◽  
Complex Impedance ◽  
Silver Sulfide ◽  
Electrical Circuit ◽  
Cole Diagram ◽  
Before And After ◽  
Superionic Phase Transition ◽  
Frequency Dependences

Frequency dependences of dielectric loss tangent tanδ (f) and Cole-Cole diagram of thin films of silver sulfide at various temperatures in the range 0-200 ° C were studied. A comparison of experimental data with the results of calculation of electrical circuit complex impedance of Ag2S samples is made. The comparison is made for temperatures before and after semiconductor-superionic phase transition. Based on the analysis of experimental results and literature data, a microscopic model of the phase transition in Ag2S is proposed.

Low frequency damping and ultrasonic attenuation in Ti3Sn-based alloys

1994 ◽  
Vol 9 (6) ◽  
pp. 1441-1448 ◽  
Author(s):  
Catherine R. Wong ◽  
Robert L. Fleischer
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Ultrasonic Attenuation ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Low Frequencies ◽  
High Frequencies ◽  
Young’S Moduli ◽  
High Temperature Alloys ◽  
Damping Behavior

Studies of high-temperature alloys in the Ti-Sn system based on the intermetallic compound Ti3Sn have identified alloys that damp strongly both at low frequencies (0.1 to 10 Hz) and high frequencies (5 to 20 MHz). The low frequency damping behavior shows loss factors as high as 0.04 at room temperature and Young's moduli that rise with temperature from 40 °C to 100 °C for two alloys. Although the basic mechanism or mechanisms of energy dissipation are presently unknown, the alloys are notable for unusual shapes of microhardness indentations. The deformations imply that large reversible strains can occur at temperatures from 23 °C to 1150 °C.

scholarly journals Performance Analysis Of Electrical Properties Of Resin Transfer Molded Banana Leaf Reinforced Polymer Composites

2021 ◽  
Vol 23 (10) ◽  
pp. 179-194
Author(s):  
T. Rajamanikandan ◽  
◽  
Dr.S. Banumathi ◽  
Dr.R. Asokan ◽  
◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Polymer Composites ◽  
Volume Resistivity ◽  
Dissipation Factor ◽  
Loading Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Reinforced Polymer ◽  
Fibre Loading ◽  
Banana Leaf

An investigation of the electrical characteristics of banana leaf reinforced Polymer composites made by resin transfer molding (RTM) has been carried out, with special emphasis on the effects of fibre loading, frequency and temperature. Every parameter, including the dielectric constant (ɛ0), dissipation factor (tan δ), loss factor (ɛ00), and conductivity, increases with increasing fibre concentration over the whole frequency range. A minimum fibre content of 50 % is required for composites to achieve excellent performance values. This increase is large at low frequencies, minimal at middle frequencies, and negligible at extremely high frequencies, according to the results of the study. At low frequencies, the volume resistivity fluctuates in response to fibre loading, while at high frequencies, the resistivity blends together. When the temperature rises, the dielectric constant values rise as well, however once the glass transition temperature is reached, the dielectric constant values fall. This fluctuates depending on the amount of fibre present. Finally, an attempt is made to establish a relationship between the experimental value of the dielectric constant and theoretical expectations.

scholarly journals Диэлектрическая спектроскопия как метод исследования тонких пленок диоксида ванадия

2019 ◽  
Vol 89 (12) ◽  
pp. 1885
Author(s):  
А.В. Ильинский ◽  
Р.А. Кастро ◽  
М.Э. Пашкевич ◽  
Е.Б. Шадрин
Keyword(s):  
Dielectric Loss ◽  
Vanadium Dioxide ◽  
Electrical Response ◽  
Strongly Correlated ◽  
Strong Electron ◽  
Electrical Circuits ◽  
Cole Diagram ◽  
Dielectric Loss Angle ◽  
Rc Circuit ◽  
Additional Maximum

The dielectric spectra of thin (1200 Å) vanadium dioxide films, a material with strong electron-electron correlations, were studied. Both the undoped and germanium-doped VO2: Ge films were studied. For the VO2: Ge, an additional maximum has been detected in the frequency of the dielectric loss spectrum. The fine structure of the spectra was investigated and the physical interpretation of two maxima in the frequency dependence of the tangent of the dielectric loss angle and of two semi-circles on the Cole-Cole diagram was performed. The results were analyzed on the basis of the equivalent electrical circuits of the samples: a single RC-circuit for the case of an undoped VO2 film and a double-circuit  for VO2: Ge. The numerical values of the parameters of the model schemes are determined. It has been established that the complicating of equivalent circuit for VO2: Ge compared to undoped VO2 is due to the complication of the electrical response of the doped film to the influence of an electromagnetic field. It is shown that this complication is associated with the acceptor properties of a Ge impurity, which is manifested when the strongly correlated material is doped with an isoelectronic impurity.

scholarly journals Impedance Spectroscopy of Lead-Free Ferroelectric Coatings

Coatings ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 221
Author(s):  
Mariya Aleksandrova ◽  
Ivailo Pandiev
Keyword(s):  
Composite Coatings ◽  
Electrical Circuit ◽  
Ferroelectric Materials ◽  
Piezoelectric Transducers ◽  
Lead Free ◽  
Electrical Behavior ◽  
Oxide Composite ◽  
Before And After ◽  
Frequency Dependences ◽  
Good Agreement

This paper presents impedance measurements of ferroelectric structures involving lead-free oxide and polymer-oxide composite coatings for sensing and energy harvesting applications. Three different ferroelectric materials grown by conventional microfabrication technologies on solid or flexible substrates are investigated for their basic resonant characteristics. Equivalent electrical circuit models are applied to all cases to explain the electrical behavior of the structures, according to the materials type and thickness. The analytical results show good agreement with the experiments carried out on a basic types of excited thin-film piezoelectric transducers. Additionally, temperature and frequency dependences of the dielectric permittivity and losses are measured for the polymer-oxide composite device in relation with the surface morphology before and after introduction of the polymer to the functional film.

Effect of Blowing Agent on Cell Morphology and Acoustic Absorption of Natural Rubber Foam

2015 ◽  
Vol 804 ◽  
pp. 25-29 ◽  
Author(s):  
Wanlop Harnnarongchai ◽  
Kantima Chaochanchaikul
Keyword(s):  
Natural Rubber ◽  
Cell Size ◽  
Cell Morphology ◽  
Foam Cell ◽  
Adsorption Coefficient ◽  
Low Frequencies ◽  
Potassium Oleate ◽  
High Frequencies ◽  
Blowing Agent ◽  
Open Cell Foam

The sound absorbing efficiency of natural rubber (NR) foam is affected by the cell morphology of foam. Potassium oleate (K-oleate) and sodium bicarbonate (NaHCO3) were used as blowing agents to create open-cell foam. Amounts of the blowing agent were varied from 0.5 to 8.0 part per hundred of rubber (phr) to evaluate cell size and number of foam cell as well as sound adsorption coefficient of NR foam. The NR foam specimens were prepared using mould and air-circulating oven for vulcanizing and foaming processes. The results indicated that K-oleate at 2.0 phr and NaHCO3 at 0.5 phr led to form NR foam with the smallest cell size and the largest number of foam cell. At low frequencies, the optimum sound adsorption coefficient of NR foam was caused by filling K-oleate 2 phr. However, that of NR foam at high frequencies was provided by 0.5 phr-NaHCO3 addition.

Hearing loss in diabetics

1993 ◽  
Vol 107 (3) ◽  
pp. 179-182 ◽  
Author(s):  
J. R. Cullen ◽  
M. J. Cinnamond
Keyword(s):  
Hearing Loss ◽  
Sensorineural Deafness ◽  
Insulin Dosage ◽  
Speech Discrimination ◽  
Low Frequencies ◽  
High Frequencies ◽  
History Of ◽  
Insulin Dependent ◽  
Stapedial Reflex ◽  
The Relationship

The relationship between diabetes and senbsorineural hearing loss has been disputed. This study compares 44 insulin-dependent diabetics with 38 age and sex matched controls. All had pure tone and speech audiometry performed, with any diabetics showing sensorineural deafness undergoing stapedial reflecx decat tests. In 14 diabetics stapedial reflex tests showed no tone decay in any patient, but seven showed evidence of recruitment. Analysis of vaiance showed the diabetics to be significantly deafer than the control population.The hearing loss affected high frequencies in both sexes, but also low frequencies in the male. Speech discrimination scores showed no differences. Further analysis by sex showed the males to account for most of the differences. Analysys of the audiograms showered mostly a high tone loss. Finally duration of disbetes, insulin dosage and family history of diabtes were not found to have a significant effect on threshold.

scholarly journals Electrical Capacitance Characteristics of Wood Chips at Low Frequency Ranges: A Cheap Tool for Quality Assessment

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3494
Author(s):  
Jakub Lev ◽  
Václav Křepčík ◽  
Egidijus Šarauskis ◽  
František Kumhála
Keyword(s):  
Moisture Content ◽  
Linear Models ◽  
Economic Value ◽  
Wood Chip ◽  
Principal Component ◽  
Dissipation Factor ◽  
Industrial Applications ◽  
Wood Chips ◽  
Electrical Capacitance ◽  
Low Frequencies

Moisture content is one of the most important parameters related to the quality of wood chips that affects both the calorific and economic value of fuel chips. For industrial applications, moisture content needs to be detected quickly. For this purpose, various indirect moisture content measurement methods (e.g., capacitance, NIR, microwave, ECT, X-ray CT, and nuclear MR) have been investigated with different results in the past. Nevertheless, determining wood chip moisture content in real time is still a challenge. The main aim of this article was therefore to analyze the dielectric properties of wood chips at low frequencies (10 kHz–5 MHz) and to examine the possibility of using these properties to predict wood chip moisture content and porosity. A container-type probe was developed for this purpose. The electrical capacitance and dissipation factor of wood chips with different moisture content was measured by an LCR meter at 10 kHz, 50 kHz, 100 kHz, 500 kHz, 1 MHz, and 5 MHz frequencies. Wood chip porosity was also measured using a gas displacement method. Linear models for moisture content and porosity prediction were determined by backward stepwise linear regression. Mathematical model was developed to better understand the physical relationships between moisture content, porosity, and electrical capacitance. These models were able to predict the moisture content of observed quantities of wood chips with the required accuracy (R2 = 0.9−0.99). This finding opens another path to measuring the moisture content and porosity of wood chips in a relatively cheap and fast way and with adequate precision. In addition, principal component analysis showed that it is also possible to distinguish between individual wood chip fraction sizes from the information obtained.

Use of Measured Mobility to Improve SEA Predictions in the Mid-Frequency Range

1999 ◽  
Author(s):  
Jerome E. Manning
Keyword(s):  
Dynamic Systems ◽  
Broad Band ◽  
Measured Data ◽  
Hybrid Technique ◽  
Complex Dynamic ◽  
Low Frequencies ◽  
Large Variability ◽  
High Frequencies ◽  
Complex Dynamic Systems ◽  
Light Coupling

Abstract Statistical energy analysis provides a technique to predict acoustic and vibration levels in complex dynamic systems. The technique is most useful for broad-band excitation at high frequencies where many modes contribute to the response in any given frequency band. At mid and low frequencies, the number of modes contributing to the response may be quite small. In this case SEA predictions show large variability from measured data and may not be useful for vibroacoustic design. This paper focuses on the use of measured data to improve the accuracy of the predictions. Past work to measure the SEA coupling and damping loss factors has not been successful for a broad range of systems that do not have light coupling. This paper introduces a new hybrid SEA technique that combines measured mobility functions with analytical SEA predictions. The accuracy of the hybrid technique is shown to be greatly improved at mid and low frequencies.

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