WorldWideScience

Sample records for frequency dielectric properties

  1. Dielectric properties of materials at microwave frequencies

    Directory of Open Access Journals (Sweden)

    Ivo Křivánek

    2008-01-01

    Full Text Available The paper introduces the review of the present state of art in the measurement of the interaction of electromagnetic waves with different kinds of materials. It is analysis of the possibilities of the mea­surement of the interaction of high frequencies waves (microwaves with materials and proposal of the experimental method for the studies mentioned above.The electromagnetic field consists of two components: electric and magnetic field. The influence of these components on materials is different. The influence of the magnetic field is negligible and it has no impact on practical use. The influence of the electric field is strong as the interaction between them results in the creation of electric currents in the material (Křivánek and Buchar, 1993.Experiments focused on the evaluation of the complex dielectric permitivity of different materials have been performed. The permitivity of solid material is also measurable by phasemethod, when the specimen is a part of transmission sub-circuit. Microwave instrument for complex permittivity measurement works in X frequency band (8.2–12.5 GHz, the frequency 10.1 GHz was used for all the measurement in the laboratory of physics, Mendel University in Brno. The extensive number of experimental data have been obtained for different materials. The length of the square side of the ae­rial open end was 50 mm and internal dimensions of waveguides were 23 mm × 10 mm. The samples have form of the plate shape with dimensions 150 mm × 150 mm × 4 mm.

  2. Technique for Performing Dielectric Property Measurements at Microwave Frequencies

    Science.gov (United States)

    Barmatz, Martin B.; Jackson, Henry W.

    2010-01-01

    A paper discusses the need to perform accurate dielectric property measurements on larger sized samples, particularly liquids at microwave frequencies. These types of measurements cannot be obtained using conventional cavity perturbation methods, particularly for liquids or powdered or granulated solids that require a surrounding container. To solve this problem, a model has been developed for the resonant frequency and quality factor of a cylindrical microwave cavity containing concentric cylindrical samples. This model can then be inverted to obtain the real and imaginary dielectric constants of the material of interest. This approach is based on using exact solutions to Maxwell s equations for the resonant properties of a cylindrical microwave cavity and also using the effective electrical conductivity of the cavity walls that is estimated from the measured empty cavity quality factor. This new approach calculates the complex resonant frequency and associated electromagnetic fields for a cylindrical microwave cavity with lossy walls that is loaded with concentric, axially aligned, lossy dielectric cylindrical samples. In this approach, the calculated complex resonant frequency, consisting of real and imaginary parts, is related to the experimentally measured quantities. Because this approach uses Maxwell's equations to determine the perturbed electromagnetic fields in the cavity with the material(s) inserted, one can calculate the expected wall losses using the fields for the loaded cavity rather than just depending on the value of the fields obtained from the empty cavity quality factor. These additional calculations provide a more accurate determination of the complex dielectric constant of the material being studied. The improved approach will be particularly important when working with larger samples or samples with larger dielectric constants that will further perturb the cavity electromagnetic fields. Also, this approach enables the ability to have a

  3. Temperature Dependence of the Radio-Frequency Dielectric Properties of Chicken Meat

    Science.gov (United States)

    Dielectric properties of chicken breast meat were measured with an open-ended coaxial-line probe between 200 MHz and 20 GHz at temperature ranging from -20 oC to +25 oC. At a given frequency, the temperature dependence reveals a sharp increase of the dielectric constant and dielectric loss factor a...

  4. Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

    OpenAIRE

    Gaiser, Peter W.; Anguelova, Magdalena D.

    2012-01-01

    Foam fraction can be retrieved from space-based microwave radiometric data at frequencies from 1 to 37 GHz. The retrievals require modeling of ocean surface emissivity fully covered with sea foam. To model foam emissivity well, knowledge of foam properties, both mechanical and dielectric, is necessary because these control the radiative processes in foam. We present a physical description of foam dielectric properties obtained from the foam dielectric constant including foam skin depth; foam ...

  5. Dielectric properties and heating rate of broccoli powder as related to radio-frequency heating

    Science.gov (United States)

    Recently, Salmonella contamination was identified in low-moisture foods including dried vegetable powder. Radio Frequency (RF) dielectric heating is a potential alternative pasteurization method with short heating time. Dielectric properties of broccoli powder with 6.9, 9.1, 12.2, and 14.9%, w. b....

  6. Temperature and Frequency Dependent Empirical Models of Dielectric Properties of Sunflower and Olive Oil

    Directory of Open Access Journals (Sweden)

    J. Vrba

    2013-12-01

    Full Text Available In this article, a known concept and measurement probe geometry for the estimation of the dielectric properties of oils have been adapted. The new probe enables the~measurement in the frequency range of 1 to 3000 MHz. Additionally, the measurement probe has been equipped with a~heat exchanger, which has enabled us to measure the dielectric properties of sunflower and olive oil as well as of two commercial emulsion concentrates. Subsequently, corresponding linear empirical temperature and frequency dependent models of the dielectric properties of the above mentioned oils and concentrates have been created. The dielectric properties measured here as well as the values obtained based on the empirical models created here match the data published in professional literature very well.

  7. Dielectric Properties of Zinc Sulfide Concentrate during the Roasting at Microwave Frequencies

    Directory of Open Access Journals (Sweden)

    Guangjun He

    2017-02-01

    Full Text Available Microwave technology has a potential application in the extraction of zinc from sulphide ores, knowledge of the dielectric properties of these ores plays a major role in the microwave design and simulation for any process. The dielectric properties of zinc sulfide concentrate for two different apparent densities-1.54 and 1.63 g/cm3-have been measured by using the resonance cavity perturbation technique at 915 and 2450 MHz during the roasting process for the temperature ranging from room temperature to 850 °C. The variations of dielectric constant, the dielectric loss factor, the dielectric loss tangent and the penetration depth with the temperature, frequency and apparent density have been investigated numerically. The results indicate that the dielectric constant increases as the temperature increases and temperature has a pivotal effect on the dielectric constant, while the dielectric loss factor has a complicated change and all of the temperature, frequency and apparent density have a significant impact to dielectric loss factor. Zinc sulfide concentrate is high loss material from 450 to 800 °C on the basis of theoretical analyses of dielectric loss tangent and penetration depth, its ability of absorbing microwave energy would be enhanced by increasing the apparent density as well. The experimental results also have proved that zinc sulfide concentrate is easy to be heated by microwave energy from 450 to 800 °C. In addition, the experimental date of dielectric constant and loss factor can be fitted perfectly by Boltzmann model and Gauss model, respectively

  8. A study of frequency dependent electrical and dielectric properties of NiO nanoparticles

    Science.gov (United States)

    Usha, V.; Kalyanaraman, S.; Vettumperumal, R.; Thangavel, R.

    2017-01-01

    Nickel oxide nanoparticles were synthesized using low cost sol-gel method. The structure of as prepared NiO nanoparticles has been confirmed from X-ray diffraction (XRD), scanning electron microscope with energy dispersive X-ray (SEM and EDX) spectroscopic analysis. The electrical and dielectric properties were characterized by complex impedance spectroscopy as a function of frequency at different temperatures. To study the dielectric behavior of the nanoparticles different plots like Nyquist plot, modulus plot and Bode plot were used. Also the frequency dependent ac conductivity is analyzed and the activation energy is calculated. The dielectric constant and dielectric loss as a function of frequency at various temperatures are also studied.

  9. Comparative study of low frequency dielectric properties of Hexyloxybenzylidine hexylaniline and Heptyloxybenzylidine hexylaniline

    Science.gov (United States)

    Singh, K. N.; Gogoi, B.; Dubey, R.; Singh, N. M.; Sharma, H. B.; Alapati, P. R.

    2016-06-01

    This article presents a comparative study of low frequency dielectric properties of two Alkyloxybenzylidine alkylaniline compounds—Hexyloxybenzylidine hexylaniline (6O.6) and Heptyloxybenzylidine hexylaniline (7O.6). Dielectric study is made by using cells with ITO coated surface pretreated with polyvinyl alcohol as the aligning layer. We have found that the switching of dielectric anisotropy from negative to positive value is related to the change in orientation of alkyloxy dipole. It indicates 6O.6 (and lower members) to be negative dielectric anisotropic material while 7O.6 (and higher members) to be positive dielectric anisotropic materials. Further comparative study on the interfacial polarization between the two types of interfaces (PVA-6O.6 and PVA-7O.6) with different relaxation times support the differences of the two liquid crystal samples. The dc electric field characteristics of the two samples are drastically different in behaviour and can be explained satisfactorily on the interplay between the dipole orientation and the ionic motion.

  10. An electrodeless system for measurement of liquid sample dielectric properties in radio frequency band.

    Science.gov (United States)

    Hartwig, V; Giovannetti, G; Vanello, N; Costantino, M; Landini, L; Benassi, A

    2006-01-01

    An electrodeless measurement system based on a resonant circuit is proposed for the measurement of dielectric properties of liquid samples at RF (radio frequency). Generally, properties as dielectric constant, loss factor and conductivity are measured by parallel plate capacitor cells: this method has several limitations in the case of particular liquid samples and in the range of radiofrequencies. Our method is based on the measurements of resonance frequency and quality factor of a LC resonant circuit in different measuring conditions, without and with the liquid sample placed inside a test tube around which the home made coil is wrapped. The measurement is performed using a network analyzer and a dual loop probe, inductively coupled with the resonant circuit. One of the advantages of this method is the contactless between the liquid sample and the measurement electrodes. In this paper the measurement system is described and test measurements of conventional liquids dielectric properties are reported.

  11. Dielectric properties of almond kernels associated with radio frequency and microwave pasteurization.

    Science.gov (United States)

    Li, Rui; Zhang, Shuang; Kou, Xiaoxi; Ling, Bo; Wang, Shaojin

    2017-02-10

    To develop advanced pasteurization treatments based on radio frequency (RF) or microwave (MW) energy, dielectric properties of almond kernels were measured by using an open-ended coaxial-line probe and impedance analyzer at frequencies between 10 and 3000 MHz, moisture contents between 4.2% to 19.6% w.b. and temperatures between 20 and 90 °C. The results showed that both dielectric constant and loss factor of the almond kernels decreased sharply with increasing frequency over the RF range (10-300 MHz), but gradually over the measured MW range (300-3000 MHz). Both dielectric constant and loss factor of almond kernels increased with increasing temperature and moisture content, and largely enhanced at higher temperature and moisture levels. Quadratic polynomial equations were developed to best fit the relationship between dielectric constant or loss factor at 27, 40, 915 or 2450 MHz and sample temperature/moisture content with R(2) greater than 0.967. Penetration depth of electromagnetic wave into samples decreased with increasing frequency (27-2450 MHz), moisture content (4.2-19.6% w.b.) and temperature (20-90 °C). The temperature profiles of RF heated almond kernels under three moisture levels were made using experiment and computer simulation based on measured dielectric properties. Based on the result of this study, RF treatment has potential to be practically used for pasteurization of almond kernels with acceptable heating uniformity.

  12. Temperature and frequency dependent dielectric properties of Ni–Mg–Zn–Co ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Patil, S.B., E-mail: sarjeraopatil97@gmail.com [Krantisinh Nana Patil College, Walwa, Sangli 416313, Maharashtra (India); Patil, R.P. [Department of Chemistry, M.H. Shinde Mahavidyalaya, Tisangi 416206, Maharashtra (India); Ghodake, J.S. [Department of Physics, Padmabhushan Dr. Vasantraodada Patil College, Tasgaon, Sangli 416312, Maharashtra (India); Chougule, B.K. [Materials Research Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, Maharashtra (India)

    2014-01-15

    The ferrites having general formula Ni{sub 0.5−x}Mg{sub x−0.01}Zn{sub 0.5−y}Co{sub y+0.01}Fe{sub 2}O{sub 4} (x=0.1, 0.2, 0.3, 0.4 and y=0.1, 0.2, 0.3, 0.4) were prepared by ceramic method. The X-ray diffraction studies of compositions reveal formation of single-phase cubic spinal structure. Dielectric properties such as dielectric constant ε′, dielectric loss tangent (tan δ), and ac resistivity were measured at room temperature as a function of frequency in the range from 1 kHz to 1 MHz. The plots of dielectric constant ε′ vs frequency show a normal dielectric behavior of spinel ferrites. The variation of loss tangent (tan δ) as a function of frequency shows a decreasing trend for all the samples except for the composition with x=0.3 and y=0.1, and y=0.2. The variation of ac resistivity with frequency of all the samples shows a decreasing trend with increase in frequency, a normal behavior of ferrites. All the variations are explained on the basis of Fe{sup 2+}/Fe{sup 3+} ion concentration on octahedral sites as well as the electronic hopping between Fe{sup 2+}↔Fe{sup 3+} ions. - Highlights: • Ni{sub 0.5−x}Mg{sub x−0.01}Zn{sub 0.5−y}Co{sub y+0.01}Fe{sub 2}O{sub 4} were prepared by ceramic method. • Single-phase cubic spinal structure. • Normal dielectric behavior.

  13. Dielectric properties and emissivity of seawater at C-band microwave frequency.

    Science.gov (United States)

    Murugkar, A G; Joshi, A S; Kurtadikar, M L

    2012-10-01

    Microwave remote sensing applications over ocean using radar and radiometers, a precise knowledge of emissivity and reflectivity, are required. Emissivity of ocean surface is a function of the surface configuration, frequency of radiation, temperature and its dielectric properties. The emissivity of a smooth ocean surface at a particular wavelength is determined by its complex dielectric properties. In present study, laboratory measurements of complex dielectric properties, real part epsilon', and imaginary part epsilon", of surface seawater samples collected from Bay of Bengal and Arabian Sea are carried out. Measurements of these seawater samples are done at 5 GHz and 30 degrees C using an automated C-band microwave bench set up. The salinity of samples is also measured using autosalinometer. The salinity values are used to determine epsilon' and epsilon" using the Debye equations. The normal incidence emissivity and brightness temperature values for smooth sea surface are reported for surface samples. The dielectric constant epsilon' decreases and dielectric loss increases with increase in salinity at 5 GHz and 30 degrees C. At normal incidence, emissivity is almost constant for varying salinities.

  14. Dielectric properties of almond kernels associated with radio frequency and microwave pasteurization

    Science.gov (United States)

    Li, Rui; Zhang, Shuang; Kou, Xiaoxi; Ling, Bo; Wang, Shaojin

    2017-01-01

    To develop advanced pasteurization treatments based on radio frequency (RF) or microwave (MW) energy, dielectric properties of almond kernels were measured by using an open-ended coaxial-line probe and impedance analyzer at frequencies between 10 and 3000 MHz, moisture contents between 4.2% to 19.6% w.b. and temperatures between 20 and 90 °C. The results showed that both dielectric constant and loss factor of the almond kernels decreased sharply with increasing frequency over the RF range (10–300 MHz), but gradually over the measured MW range (300–3000 MHz). Both dielectric constant and loss factor of almond kernels increased with increasing temperature and moisture content, and largely enhanced at higher temperature and moisture levels. Quadratic polynomial equations were developed to best fit the relationship between dielectric constant or loss factor at 27, 40, 915 or 2450 MHz and sample temperature/moisture content with R2 greater than 0.967. Penetration depth of electromagnetic wave into samples decreased with increasing frequency (27–2450 MHz), moisture content (4.2–19.6% w.b.) and temperature (20–90 °C). The temperature profiles of RF heated almond kernels under three moisture levels were made using experiment and computer simulation based on measured dielectric properties. Based on the result of this study, RF treatment has potential to be practically used for pasteurization of almond kernels with acceptable heating uniformity. PMID:28186149

  15. Dielectric properties of almond kernels associated with radio frequency and microwave pasteurization

    Science.gov (United States)

    Li, Rui; Zhang, Shuang; Kou, Xiaoxi; Ling, Bo; Wang, Shaojin

    2017-02-01

    To develop advanced pasteurization treatments based on radio frequency (RF) or microwave (MW) energy, dielectric properties of almond kernels were measured by using an open-ended coaxial-line probe and impedance analyzer at frequencies between 10 and 3000 MHz, moisture contents between 4.2% to 19.6% w.b. and temperatures between 20 and 90 °C. The results showed that both dielectric constant and loss factor of the almond kernels decreased sharply with increasing frequency over the RF range (10–300 MHz), but gradually over the measured MW range (300–3000 MHz). Both dielectric constant and loss factor of almond kernels increased with increasing temperature and moisture content, and largely enhanced at higher temperature and moisture levels. Quadratic polynomial equations were developed to best fit the relationship between dielectric constant or loss factor at 27, 40, 915 or 2450 MHz and sample temperature/moisture content with R2 greater than 0.967. Penetration depth of electromagnetic wave into samples decreased with increasing frequency (27–2450 MHz), moisture content (4.2–19.6% w.b.) and temperature (20–90 °C). The temperature profiles of RF heated almond kernels under three moisture levels were made using experiment and computer simulation based on measured dielectric properties. Based on the result of this study, RF treatment has potential to be practically used for pasteurization of almond kernels with acceptable heating uniformity.

  16. Frequency and Temperature Dependences of Dielectric Dispersion and Electrical Properties of Polyvinylidene Fluoride/Expanded Graphite Composites

    National Research Council Canada - National Science Library

    Li, Yu Chao; Li, Robert Kwok Yiu; Tjong, Sie Chin

    2010-01-01

    ...) by direct melt blending process. The electrical conductivity and dielectric properties of resulting PVDF/EG composites were investigated in a wide range of frequencies from [superscript]102[/superscript] to [superscript]108[/superscript] Hz...

  17. The High-Frequency Dielectric Properties of Glass Fibre Reinforced Plastic and Honeycomb Layers

    Science.gov (United States)

    1989-06-29

    The dielectric constant and the dielectric loss angle tangent of glass fibre reinforced plastic are both relatively small; it is a good wave...practical value. This paper introduces the work we have done in this area. The dielectric properties of glass fibre reinforced plastic have a close

  18. Dielectric and Radiative Properties of Sea Foam at Microwave Frequencies: Conceptual Understanding of Foam Emissivity

    Directory of Open Access Journals (Sweden)

    Peter W. Gaiser

    2012-04-01

    Full Text Available Foam fraction can be retrieved from space-based microwave radiometric data at frequencies from 1 to 37 GHz. The retrievals require modeling of ocean surface emissivity fully covered with sea foam. To model foam emissivity well, knowledge of foam properties, both mechanical and dielectric, is necessary because these control the radiative processes in foam. We present a physical description of foam dielectric properties obtained from the foam dielectric constant including foam skin depth; foam impedance; wavelength variations in foam thickness, roughness of foam layer interfaces with air and seawater; and foam scattering parameters such as size parameter, and refraction index. Using these, we analyze the scattering, absorption, reflection and transmission in foam and gain insights into why volume scattering in foam is weak; why the main absorption losses are confined to the wet portion of the foam; how the foam impedance matching provides the transmission of electromagnetic radiation in foam and maximizes the absorption; and what is the potential for surface scattering at the foam layers boundaries. We put all these elements together and offer a conceptual understanding for the high, black-body-like emissivity of foam floating on the sea surface. We also consider possible scattering regimes in foam.

  19. Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

    Energy Technology Data Exchange (ETDEWEB)

    Hakala, J. Alexandra [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Stanchina, William [Univ. of Pittsburgh, PA (United States); National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Soong, Yee [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States); Hedges, Sheila [National Energy Technology Lab. (NETL), Pittsburgh, PA, (United States)

    2011-01-01

    Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (<200° C) and constant oil shale grade, both the relative dielectric constant (ε') and imaginary permittivity (ε'') decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, ε' decreases or remains constant with oil shale grade, while ε'' increases or shows no trend with oil shale grade. At higher temperatures (>200º C) and constant frequency, epsilon' generally increases with temperature regardless of grade while ε'' fluctuates. At these temperatures, maximum values for both ε' and ε'' differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools.

  20. Influence of frequency, grade, moisture and temperature on Green River oil shale dielectric properties and electromagnetic heating processes

    Energy Technology Data Exchange (ETDEWEB)

    Hakala, J. Alexandra; Soong, Yee; Hedges, Sheila [National Energy Technology Laboratory, Pittsburgh, PA (United States); Stanchina, William [National Energy Technology Laboratory, Pittsburgh, PA (United States); Department of Electrical and Computer Engineering, University of Pittsburgh, PA (United States)

    2011-01-15

    Development of in situ electromagnetic (EM) retorting technologies and design of specific EM well logging tools requires an understanding of various process parameters (applied frequency, mineral phases present, water content, organic content and temperature) on oil shale dielectric properties. In this literature review on oil shale dielectric properties, we found that at low temperatures (< 200 C) and constant oil shale grade, both the relative dielectric constant ({epsilon}') and imaginary permittivity ({epsilon}'') decrease with increased frequency and remain constant at higher frequencies. At low temperature and constant frequency, {epsilon}' decreases or remains constant with oil shale grade, while {epsilon}'' increases or shows no trend with oil shale grade. At higher temperatures (> 200 C) and constant frequency, {epsilon}' generally increases with temperature regardless of grade while {epsilon}'' fluctuates. At these temperatures, maximum values for both {epsilon}' and {epsilon}'' differ based upon oil shale grade. Formation fluids, mineral-bound water, and oil shale varve geometry also affect measured dielectric properties. This review presents and synthesizes prior work on the influence of applied frequency, oil shale grade, water, and temperature on the dielectric properties of oil shales that can aid in the future development of frequency- and temperature-specific in situ retorting technologies and oil shale grade assay tools. (author)

  1. Measurement of the dielectric properties of the epidermis and dermis at frequencies from 0.5 GHz to 110 GHz

    Science.gov (United States)

    Sasaki, K.; Wake, K.; Watanabe, S.

    2014-08-01

    Numerous studies have reported the measurements of the dielectric properties of the skin. Clarifying the manner in which the human body interacts with electromagnetic waves is essential for medical research and development, as well as for the safety assessment of electromagnetic wave exposure. The skin comprises several layers: the epidermis, the dermis, and the subcutaneous fat. Each of these skin layers has a different constitution; however, the previous measurements of their dielectric properties were typically conducted on tissue which included all three layers of the skin. This study presents novel dielectric property data for the epidermis and dermis with in vitro measurement at frequencies ranging from 0.5 GHz to 110 GHz. Measured data was compared with literature values; in particular, the findings were compared with Gabriel’s widely used data on skin dielectric properties. The experimental results agreed with the data reported by Gabriel for the dermis of up to 20 GHz, which is the upper limit of the range of frequencies at which Gabriel reported measurements. For frequencies of 20-100 GHz, the experimental results indicated larger values than those extrapolated from Gabriel’s data using parametric expansion. For frequencies over 20 GHz, the dielectric properties provided by the parametric model tend toward the experimental results for the epidermis with increasing frequency.

  2. Assessing Chicken Meat Freshness through Measurement of Radio-Frequency Dielectric Properties

    Science.gov (United States)

    Change in freshness of chicken meat was assessed through measurement of the dielectric properties with a vector network analyzer and an open-ended coaxial-line probe between 200 MHz and 20 GHz at 23 oC. Chicken meat samples were stored in a refrigerator for 8 days at 4 oC. Changes in dielectric cons...

  3. Dielectric properties of fly ash

    Indian Academy of Sciences (India)

    S C Raghavendra; R L Raibagkar; A B Kulkarni

    2002-02-01

    This paper reports the dielectric properties of fly ash. The dielectric measurements were performed as a function of frequency and temperature. The sample of fly ash shows almost similar behaviour in the frequency and temperature range studied. The large value of dielectric constant in the typical frequency range is because of orientation polarization and tight binding force between the ions or atoms in the fly ash. The sample of fly ash is of great scientific and technological interest because of its high value of dielectric constant (104).

  4. Cole-Cole parameters for the dielectric properties of porcine tissues as a function of age at microwave frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Peyman, A; Gabriel, C, E-mail: Azadeh.peyman@hpa.org.u [MCL-P, 17B Woodford Road, London E18 2EL (United Kingdom)

    2010-08-07

    We have applied the Cole-Cole expression to the dielectric properties of tissues in the frequency range 0.4-10 GHz. The data underpinning the model relate to pig tissue as a function of age. Altogether, we provide the Cole-Cole parameters for 14 tissue types at three developmental stages. (note)

  5. Cole-Cole parameters for the dielectric properties of porcine tissues as a function of age at microwave frequencies.

    Science.gov (United States)

    Peyman, A; Gabriel, C

    2010-08-01

    We have applied the Cole-Cole expression to the dielectric properties of tissues in the frequency range 0.4-10 GHz. The data underpinning the model relate to pig tissue as a function of age. Altogether, we provide the Cole-Cole parameters for 14 tissue types at three developmental stages.

  6. Mesomorphic and dielectric properties of esters useful for formulation of nematic mixtures for dual frequency addressing system

    Science.gov (United States)

    Ziobro, D.; Kula, P.; Dziaduszek, J.; Filipowicz, M.; DĄbrowski, R.; Parka, J.; Czub, J.; Urban, S.; Wu, S. T.

    2009-03-01

    Mesomorphic and dielectric properties of three homologous series of two and three ring fluorosubstituted esters are described. They are 4-cyano-3-fluorophenyl 4-alkyloxy-2-fluorobenzoates, 4-cyano-3-fluorophenyl 4-(4-alkylbenzoyloxy)-2-fluorobenzoates and 3-fluoro-4-cyanophenyl, or 3-fluoro-4-isothiocyanatophenyl or 3,4-difluorophenyl 4'-alkyl-2,3-difluoro-biphenyl-4-carboxylates. The compounds exhibit the nematic mesophase accompanied by the smectic A or smectic C mesophase in some cases. Most of them show strong dependence of the dielectric anisotropy Δɛ upon frequency, at low frequencies Δɛ reaches a value ˜200, while at high frequencies a small negative dielectric anisotropy appears.

  7. Change in Dielectric Properties in the Microwave Frequency Region of Polypyrrole–Coated Textiles during Aging

    Directory of Open Access Journals (Sweden)

    Eva Hakansson

    2016-07-01

    Full Text Available Complex permittivity of conducting polypyrrole (PPy-coated Nylon-Lycra textiles is measured using a free space transmission measurement technique over the frequency range of 1–18 GHz. The aging of microwave dielectric properties and reflection, transmission and absorption for a period of 18 months is demonstrated. PPy-coated fabrics are shown to be lossy over the full frequency range. The levels of absorption are shown to be higher than reflection in the tested samples. This is attributed to the relatively high resistivity of the PPy-coated fabrics. Both the dopant concentration and polymerisation time affect the total shielding effectiveness and microwave aging behaviour. Distinguishing either of these two factors as being exclusively the dominant mechanism of shielding effectiveness is shown to be difficult. It is observed that the PPy-coated Nylon-Lycra samples with a p-toluene sulfonic acid (pTSA concentration of 0.015 M and polymerisation times of 60 min and 180 min have 37% and 26% decrease in total transmission loss, respectively, upon aging for 72 weeks at room temperature (20 °C, 65% Relative humidity (RH. The concentration of the dopant also influences the microwave aging behaviour of the PPy-coated fabrics. The samples with a higher dopant concentration of 0.027 mol/L pTSA are shown to have a transmission loss of 32.6% and 16.5% for short and long polymerisation times, respectively, when aged for 72 weeks. The microwave properties exhibit better stability with high dopant concentration and/or longer polymerization times. High pTSA dopant concentrations and/or longer polymerisation times result in high microwave insertion loss and are more effective in reducing the transmission and also increasing the longevity of the electrical properties.

  8. Dielectric Properties and Oxidation Roasting of Molybdenite Concentrate by Using Microwave Energy at 2.45 GHz Frequency

    Science.gov (United States)

    Yonglin, Jiang; Bingguo, Liu; Peng, Liu; Jinhui, Peng; Libo, Zhang

    2017-09-01

    Conversion of electromagnetic energy into heat depends largely on the dielectric properties of the material being treated. Therefore, determining the dielectric properties of molybdenite concentrate and its microwave power penetration depth in relation to a temperature increment at the commercial frequency of 2.45 GHz is necessary to design industrial microwave processing units. In this study, the dielectric constants increased as the temperature increased in the entire experimental range. The loss factor presented an opposite trend, except for 298 K to 373 K (25 °C to 100 °C) in which a cavity perturbation resonator was used. The plots of nonlinear surface fitting indicate that the increase in dielectric loss causes a considerable decrease in penetration depth, but the dielectric constants exert a small positive effect. The thermogravimetric analysis (TGA-DSC) of the molybdenite concentrate was carried out to track its thermal decomposition process, aim to a dielectric analysis during the microwave heating. MoO3 was prepared from molybdenite concentrate through oxidation roasting in a microwave heating system and a resistance furnace, respectively. The phase transitions and morphology evolutions during oxidation roasting were characterized through X-ray diffraction and scanning electron microscopy. Results show that microwave thermal technique can produce high-purity molybdenum trioxide.

  9. Magneto-dielectric properties of doped ferrite based nanosized ceramics over very high frequency range

    Directory of Open Access Journals (Sweden)

    Ashish Saini

    2016-06-01

    Full Text Available In the present study, indium doped nano sized nickel zinc cobalt based ferrite ceramics with composition Ni0.5Zn0.3Co0.2InxFe2-xO4 (x = 0.2 and 0.4 were synthesized by a co-precipitation technique. Powdered sample has been pre-sintered at 800 °C, pressed into toroids and finally sintered at 1000 °C. The single phase formation of the presintered powder has been confirmed by X ray diffraction (XRD. The average particle size of the presintered powder has been estimated by field emission scanning electron microscope (FESEM and found to be about ~60 nm for x = 0.2 and ~80 nm at x = 0.4. The electromagnetic characterization has been made using vector network analyzer. High value of permeability (17.3 and 15.2 for x = 0.2 and 0.4 respectively with low magnetic loss tangent of 10−1 order were obtained. Permittivity of 8.2 and 10, and dielectric loss tangent of the order of 10−2 were also achieved. With the measured electromagnetic parameters, miniaturization factor of 12.32 and normalized characteristic impedance close to unity (1.23 were obtained up to 100 MHz frequency. These fascinating parameters definitely propose Ni0.5Zn0.3Co0.2In0.4Fe1.6O4 ceramics as a substrate material for miniaturized antenna in very high frequency band. Possible reasons and mechanisms of electromagnetic properties for different concentrations of indium are discussed in the paper.

  10. Modelling of the dielectric properties of trabecular bone samples at microwave frequency

    CERN Document Server

    Irastorza, Ramiro M; Carlevaro, Carlos M; Vericat, Fernando

    2013-01-01

    In this paper the dielectric properties of human trabecular bone are evaluated under physiological condition in the microwave range. Assuming a two components medium, simulation and experimental data are presented and discussed. A special experimental setup is developed in order to deal with inhomogeneous samples. Simulation data are obtained using finite difference time domain from a realistic sample. The bone mineral density of the samples are also measured. The simulation and experimental results of the present study suggest that there is a negative relation between bone volume fraction (BV/TV) and permittivity (conductivity): the higher the BV/TV the lower the permittivity (conductivity). This is in agreement with the recently published in vivo data. Keywords: Bone dielectric properties, Microwave tomography, Finite difference time domain.

  11. Influence of mashed potato dielectric properties and circulating water electric conductivity on radio frequency heating at 27 MHz.

    Science.gov (United States)

    Wang, Jian; Olsen, Robert G; Tang, Juming; Tang, Zhongwei

    2008-01-01

    Experiments and computer simulations were conducted to systematically investigate the influence of mashed potato dielectric properties and circulating water electric conductivity on electromagnetic field distribution, heating rate, and heating pattern in packaged food during radio frequency (RF) heating processes in a 6 kW, 27 MHz laboratory scale RF heating system. Both experimental and simulation results indicated that for the selected food (mashed potato) in this study, the heating rate decreased with an increase of electric conductivity of circulating water and food salt content. Simplified analytical calculations were carried out to verify the simulation results, which further indicated that the electric field distribution in the mashed potato samples was also influenced by their dielectric properties and the electric conductivity of the surrounding circulating water. Knowing the influence of water electric conductivity and mashed potato dielectric properties on the heating rate and heating pattern is helpful in optimizing the radio frequency heating process by properly adjusting these factors. The results demonstrate that computer simulation has the ability to demonstrate influence on RF heat pattern caused by the variation of material physical properties and the potential to aid the improvement on construction and modification of RF heating systems.

  12. Dielectric properties of highly resistive GaN crystals grown by ammonothermal method at microwave frequencies

    Directory of Open Access Journals (Sweden)

    Jerzy Krupka

    2016-03-01

    Full Text Available Permittivity, the dielectric loss tangent and conductivity of semi-insulating Gallium Nitride crystals have been measured as functions of frequency from 10 GHz to 50 GHz and temperature from 295 to 560 K employing quasi TE0np mode dielectric resonator technique. Crystals were grown using ammonothermal method. Two kinds of doping were used to obtain high resistivity crystals; one with deep acceptors in form of transition metal ions, and the other with shallow Mg acceptors. The sample compensated with transition metal ions exhibited semi-insulating behavior in the whole temperature range. The sample doped with Mg acceptors remained semi-insulating up to 390 K. At temperatures exceeding 390 K the conductivity term in the total dielectric loss tangent of Mg compensated sample becomes dominant and it increases exponentially with activation energy of 1.14 eV. It has been proved that ammonothermal method with appropriate doping allows growth of high quality, temperature stable semi-insulating GaN crystals.

  13. Temperature and frequency dependent dielectric properties of electrically conducting oxidatively synthesized polyazomethines and their structural, optical, and thermal characterizations

    Science.gov (United States)

    Dineshkumar, Sengottuvelu; Muthusamy, Athianna; Chandrasekaran, J.

    2017-01-01

    Three azomethine diol monomers were synthesized by condensing with methanolic solution of aromatic aldehydes with ethylenediamine. These monomers were oxidatively polymerized using NaOCl as an oxidant. The structures of the monomers and polymers were confirmed by various spectroscopic techniques. Spectral results showed that the repeating units are linked by Csbnd C and Csbnd Osbnd C couplings. The polyazomethines have fluorescent property with high stokes shift. Solid state electrical conductivity of polymers both in I2 doped and undoped states, temperature and frequency dependent dielectric measurements were made by two probe method. The electrical conductivities of polyazomethines were compared based on the charge densities on imine nitrogens obtained from Huckel calculation. The conductivity of polymers increases with increase in iodine vapour contact time. Among the synthesized polymers PHNAE has shown high dielectric constant at low applied frequency of 50 Hz at 393 K due the presence of bulky naphthalene unit in polymer chain.

  14. Variation of Dielectric and Electrical Properties of Zr-Substituted Lead Calcium Iron Niobate with Temperature and Frequency

    Science.gov (United States)

    Puri, Maalti; Bahel, Shalini; Narang, Sukhleen Bindra

    2016-10-01

    The purpose of the present study is to improve the dielectric properties of lead calcium iron niobate with Zr substitution, and to make it suitable for multilayer capacitor applications in resonant circuits. (Pb0.45Ca0.55)(Fe0.5Nb0.5)1- y Zr y O3 dielectric ceramics where y varies from 0.00 to 0.15 in steps of 0.03, that have been synthesized by the columbite precursor method. Dielectric and electrical properties were measured as a function of frequency (10 kHz to 1 MHz) and temperature. Two frequency dependent anomalies were observed in relative permittivity ( ɛ r) versus temperature ( T) plots around 375 K and between 500 K and 575 K. The temperature coefficient of relative permittivity, ( τ ɛ ) has been improved with the substitution of (Fe0.5Nb0.5)4+ ions by Zr4+ ions at B-sites. The single semicircle, observed in Nyquist plots at different temperatures, suggests a single relaxation process in the synthesized samples. The activation energies obtained from different dependences are found to be approximately comparable.

  15. Experimental study on the dielectric properties of polyacrylate dielectric elastomer

    Science.gov (United States)

    Qiang, Junhua; Chen, Hualing; Li, Bo

    2012-02-01

    The dielectric constant of elastomeric dielectric material is an essential physical parameter, whose value may affect the electromechanical deformation of a dielectric elastomer actuator. Since the dielectric constant is influenced by several external factors as reported before, and no certain value has been confirmed to our knowledge, in the present paper, on the basis of systematical comparison of recent past literature, we conducted extensive works on the measurement of dielectric properties of VHB films, involving five influencing factors: prestretch (both equal and unequal biaxial), electrical frequency, electrode material, stress relaxation time and temperature. Experimental results directly show that the dielectric response changes according to these factors, based on which we investigate the significance of each factor, especially the interaction of two external conditions on the dielectric constant of deformable dielectric, by presenting a physical picture of the mechanism of polarization.

  16. Study of the dielectric properties of weathered granite, basalt and quartzite by means of broadband dielectric spectroscopy over a wide range of frequency and temperature.

    Science.gov (United States)

    Araujo, Steven; Delbreilh, Laurent; Antoine, Raphael; Dargent, Eric; Fauchard, Cyrille

    2016-04-01

    Broadband Dielectric Spectroscopy (BDS) allows the measurement of the complex impedance of various materials over a wide range of frequency (0.1 Hz to 2 MHz) and temperature (-150 to 400°C). Other properties can be assessed from this measurement such as permittivity and conductivity. In this study, the BDS is presented to figure out the complex behaviour of several rock parameters as a function of the temperature and frequency. Indeed, multiple processes might occur such as interfacial polarization, AC and DC conductivity. The measurements of a weathered granite, basalt and quartzite were performed. The activation energy associated to each process involved during the measurement can be calculated by following the relaxation time as a function of the temperature, taking into account the Havriliak-Négami model. The principle of the technique and the whole study is presented here and several hypothesis are advanced to explain the dielectric behaviour of rocks. Finally, as the range of frequency and temperature of the BDS method is common to several electromagnetic and electrical techniques applied in subsurface geophysics, some perspectives are proposed to better understand geophysical measurements in hydrothermal systems.

  17. Dielectric properties of agricultural products – fundamental principles, influencing factors, and measurement technirques. Chapter 4. Electrotechnologies for Food Processing: Book Series. Volume 3. Radio-Frequency Heating

    Science.gov (United States)

    In this chapter, definitions of dielectric properties, or permittivity, of materials and a brief discussion of the fundamental principles governing their behavior with respect to influencing factors are presented. The basic physics of the influence of frequency of the electric fields and temperatur...

  18. Dielectric Properties of Yttria Ceramics at High Temperature

    Institute of Scientific and Technical Information of China (English)

    Jian Chen; Zheng-Ping Gao; Jin-Ming Wang; Da-Hai Zhang

    2007-01-01

    Based on Clausius-Mosotti equation and Debye relaxation theory, the dielectric model of yttria ceramics was developed according to the dielectric loss mechanism. The dielectric properties of yttria ceramics were predicted at high temperature. The temperature dependence and frequency dependence of dielectric constant and dielectric loss were discussed, respectively.As the result, the data calculated by theoretical dielectric model are in agreement with experimental data.

  19. Temperature dependence of the dielectric properties of rubber wood

    Science.gov (United States)

    Mohammed Firoz Kabir; Wan M. Daud; Kaida B. Khalid; Haji A.A. Sidek

    2001-01-01

    The effect of temperature on the dielectric properties of rubber wood was investigated in three anisotropic directions—longitudinal, radial, and tangential, and at different measurement frequencies. Low frequency measurements were conducted with a dielectric spectrometer, and high frequencies used microwave applied with open-ended coaxial probe sensors. Dielectric...

  20. Changes in dielectric properties at 460 kHz of kidney and fat during heating: importance for radio-frequency thermal therapy

    Science.gov (United States)

    Pop, Mihaela; Molckovsky, Andrea; Chin, Lee; Kolios, Michael C.; Jewett, Michael A. S.; Sherar, Michael D.

    2003-08-01

    We have developed a system to measure the changes due to heating to high temperatures in the dielectric properties of tissues in the radio-frequency range. A two-electrode arrangement was connected to a low-frequency impedance analyser and used to measure the dielectric properties of ex vivo porcine kidney and fat at 460 kHz. This frequency was selected as it is the most commonly used for radio-frequency thermal therapy of renal tumours. Tissue samples were heated to target temperatures between 48 and 78 °C in a hot water bath and changes in dielectric properties were measured during 30 min of heating and 15 min of cooling. Results suggest a time-temperature dependence of dielectric properties, with two separate components: one a reversible, temperature-dependent effect and the other a permanent effect due to structural events (e.g. protein coagulation, fat melting) that occur in tissues during heating. We calculated temperature coefficients of 1.3 +/- 0.1% °C-1 for kidney permittivity and 1.6% °C-1 for kidney conductivity, 0.9 +/- 0.1% °C-1 for fat permittivity and 1.7 +/- 0.1% °C-1 for fat conductivity. An Arrhenius model was employed to determine the first-order kinetic rates for the irreversible changes in dielectric properties. The following Arrhenius parameters were determined: an activation energy of 57 +/- 5 kcal mol-1 and a frequency factor of (6 +/- 1) × 1034 s-1 for conductivity of kidney, an activation energy of 48 +/- 2 kcal mol-1 and a frequency factor of 6 × 1028 s-1 for permittivity of kidney. A similar analysis led to an activation energy of 31 +/- 4 kcal mol-1 and a frequency factor of (4.43 +/-1) × 1016 s-1 for conductivity of fat, and an activation energy of 40 +/- 4 kcal mol-1 and a frequency factor of 4 × 1022 s-1 for permittivity of fat. Structural events occurring during heating at different target temperatures as determined by histological analyses were correlated with the changes in the measured dielectric properties.

  1. Dielectric Properties Determination of a Stratified Medium

    Directory of Open Access Journals (Sweden)

    P. Yoiyod

    2015-04-01

    Full Text Available The method of detection of variation in dielectric properties of a material covered with another material, which requires nondestructive measurement, has numerous applications and the accurate measurement system is desirable. This paper presents a dielectric properties determination technique whereby the dielectric constant and loss factor are extracted from the measured reflection coefficient. The high frequency reflection coefficient shows the effect of the upper layer, while the dielectric properties of the lower layer can be determined at the lower frequency. The proposed technique is illustrated in 1-11 GHz band using 5 mm-thick water and 5% saline solution. The fluctuation of the dielectric properties between the high frequency and the low frequency, results from the edge diffraction in the material and the multiple reflections at the boundary of the two media, are invalid results. With the proposed technique, the dielectric properties of the lower layer can be accurately determined. The system is validated by measurement and good agreement is obtained at the frequency below 3.5 GHz. It can be applied for justifying variation of the material in the lower layer which is important in industrial process.

  2. Dielectric Behavior of Biomaterials at Different Frequencies on Room Temperature

    Science.gov (United States)

    Shrivastava, B. D.; Barde, Ravindra; Mishra, A.; Phadke, S.

    2014-09-01

    Propagation of electromagnetic (EM) waves in radiofrequency (RF) and microwave systems is described mathematically by Maxwell's equations with corresponding boundary conditions. Dielectric properties of lossless and lossy materials influence EM field distribution. For a better understanding of the physical processes associated with various RF and microwave devices, it is necessary to know the dielectric properties of media that interact with EM waves. For telecommunication and radar devices, variations of complex dielectric permittivity (referring to the dielectric property) over a wide frequency range are important. For RF and microwave applicators intended for thermal treatments of different materials at ISM (industrial, scientific, medical) frequencies, one needs to study temperature and moisture content dependencies of the Permittivity of the treated materials. Many techniques have been developed for the measurement of materials. In the present paper authors used Bones and scales of Fish taken from Narmada River (Rajghat Dist. Barwani) as biomaterials. Dielectric properties of Biomaterials with the frequency range from 1Hz to 10 MHz at room temperature with low water content were measured by in-situ performance dielectric kit. Analysis has been done by Alpha high performance impedance analyzer and LCR meters. The experimental work were carried out in Inter University Consortium UGC-DAE, CSR center Indore MP. Measured value indicates the dielectric constant (ɛ') dielectric loss (ɛ") decreases with increasing frequency while conductivity (σ) increases with frequency increased.

  3. Effect of shape of scatterers and plasma frequency on the complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals

    Science.gov (United States)

    Fathollahi Khalkhali, T.; Bananej, A.

    2016-12-01

    In this study, we analyze complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals with triangular and square lattices, composed of plasma rods with different geometrical shapes in the anisotropic tellurium background. Using the finite-difference time-domain method we discuss the maximization of the complete photonic band gap width as a function of plasma frequency and plasma rods parameters with different shapes and orientations. The numerical results demonstrate that our proposed structures represent significantly wide complete photonic band gaps in comparison to previously studied dielectric-plasma photonic crystals.

  4. Effect of annealing on the temperature-dependent dielectric properties of LaAlO3 at terahertz frequencies

    Directory of Open Access Journals (Sweden)

    Xingquan Zou

    2012-03-01

    Full Text Available We present THz conductivity of LaAlO3 (LAO as a function of temperature and annealing, using terahertz time-domain spectroscopy (THz-TDS. We observed that, after annealing, spectral weight redistribution occurs, such that the real conductivity σ1(ω changed from a featureless and almost frequency-independent spectrum, into one where peaks occur near the phonon frequencies. These phonon frequencies increase with increasing temperature. We attribute the appearance of these absorption peaks to the diffusion and relocation of oxygen vacancies. The dielectric functions of annealed LAO are well fitted with the Drude-Lorentz model.

  5. Structural, dielectric and magnetic properties of Cr-Zn doped strontium hexa-ferrites for high frequency applications

    Energy Technology Data Exchange (ETDEWEB)

    Asghar, G. [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan); Anis-ur-Rehman, M., E-mail: rehmananis@hotmail.com [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

    2012-06-15

    M-type strontium hexa-ferrite nano particles with composition SrFe{sub 12-2x}Cr{sub x}Zn{sub x}O{sub 19} (X = 0.0, 0.2, 0.4, 0.6, 0.8) were prepared by co-precipitation method and are reported for the first time. X-ray diffraction analysis confirmed the successful substitution of Cr and Zn ions in the strontium hexa-ferrite lattice. Structural morphology studied by scanning electron micrographs revealed that Cr-Zn doping inhabits the grain growth. Dielectric measurements were taken as a function of frequency in the range (10 kHz to 3 MHz). Both dielectric constants and dielectric losses were found to be decreasing with the increase in Cr-Zn concentration. As Cr-Zn doping favored the decrease in dielectric losses to a large extent (0.32-0.02) so the strontium hexa-ferrite with these dopants is very useful for high frequency applications. The frequency dependent ac conductivity increases sharply at higher frequencies due to increase in hopping frequency of electrons and decrease with the increase in doping concentration and this is due to decrease in Fe{sup 2+} ions. Temperature dependent dc electrical resistivity measurements showed a decreasing trend with the increase in Cr-Zn concentration. The M-H loop indicated that both coercivity and saturation magnetization were decreased with the increase in doping concentration. The former was decreased due to increase in grain size and later was decreased due to weak and non-magnetic cations distribution on interstitial sites.

  6. Development of a dielectric ceramic based on diatomite-titania part two: dielectric properties characterization

    Directory of Open Access Journals (Sweden)

    Medeiros Jamilson Pinto

    1998-01-01

    Full Text Available Dielectric properties of sintered diatomite-titania ceramics are presented. Specific capacitance, dissipation factor, quality factor and dielectric constant were determined as a function of sintering temperature, titania content and frequency; the temperature coefficient of capacitance was measured as a function of frequency. Besides leakage current, the dependence of the insulation resistance and the dielectric strength on the applied dc voltage were studied. The results show that diatomite-titania compositions can be used as an alternative dielectric.

  7. Low-Frequency Dependence of Conductivity and Dielectric Properties of Polyaniline/ZnFe2O4 Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    G. D. Prasanna; H. S. Jayanna; Ashok R Lamani; M. L. Dinesha; C. S. Naveen; G. J. Shankaramurthy

    2011-01-01

    Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2O4 nanoparticles.The structural,morphological and electrical properties of the samples are characterized by x-ray diffraction,Fourier transform infrared spectra and scanning electron microscopy.These results reveal the formation of polyaniline/ZnFe2O4 nanocomposites.The morphology of these samples is studied by scanning electron microscopy.Further,the ac conductivity (σac) of these composites is investigated in the frequency range of 1 kHz-10 MHz.The presence of polarons and bipolarons are responsible for the frequency dependence of ac conductivity in these nanocomposites.The ac conductivity is found to be constant up to 1 MHz and thereafter it increases steeply.The ac conductivity of 0.695S·cm-1 at room temperature is observed as the maxima for the polyaniline with 40wt% of the ZnFe2O4 nanocomposite.Polymers are known,in general,as a class of heat sensitive,flexible,electrically insulating,amorphous or semicrystalline materials.The electrical properties of polymers can be modified by the addition of inorganic materials.Nanoscale particles as fillers are attractive due to their intriguing properties arising from the nanosize and resulting large surface area.The insertion of nanoscale materials may improve the electrical and dielectric properties of the host polymers.[1]A large number of polymers are now included in the list of conducting polymers,including polyaniline,polypyrrole,polythiophene,polyparaphenylene,polyphenylene sulphide,polyphenylene vinylene,etc.%Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2OA nanoparticles. The structural, morphological and electrical properties of the samples are characterized by x-ray diffraction, Fourier transform infrared spectra and scanning electron

  8. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    -induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric......The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision...

  9. Terahertz-frequency dielectric response of liquids

    DEFF Research Database (Denmark)

    Jepsen, Peter Uhd; Møller, Uffe; Cooke, David

    -induced dipole moments. In the polar liquid water the fastest relaxational dynamics is found at terahertz frequencies, just below the first intermolecular vibrational and librational modes. In this presentation we will discuss optical terahertz spectroscopic techniques for measurement of the full dielectric......The dielectric response of liquids spans many decades in frequency. The dielectric response of a polar liquid is typically determined by relaxational dynamics of the dipolar moments of the liquid. In contrast, the dielectric response of a nonpolar liquid is determined by much weaker collision...

  10. Microwave dielectric properties of nanostructured nickel ferrite

    Indian Academy of Sciences (India)

    John Jacob; M Abdul Khadar; Anil Lonappan; K T Mathew

    2008-11-01

    Nickel ferrite is one of the important ferrites used in microwave devices. In the present work, we have synthesized nanoparticles of nickel ferrite using chemical precipitation technique. The crystal structure and grain size of the particles are studied using XRD. The microwave dielectric properties of nanostructured nickel ferrite samples of three different average grain sizes and those of two sintered samples were studied. The parameters like dielectric constant, dielectric loss and heating coefficient of the nanoparticles samples are studied in the frequency range from 2.4 to 4 GHz. The values of these parameters are compared with those of sintered pellets of the same samples. All these parameters show size dependent variations.

  11. Dielectric properties of nanosilica filled epoxy nanocomposites

    Indian Academy of Sciences (India)

    M G VEENA; N M RENUKAPPA; KUNIGAL N SHIVAKUMAR; S SEETHARAMU

    2016-04-01

    This paper presents the development of epoxy-silica nanocomposites and characterized for dielectric properties. The effect of nanosilica loading (0–20 wt%), frequency, temperature and sea water aging on these properties was studied. Transmission electron microscopy (TEM) analysis of the samples showed an excellent dispersion. However, at higher silica loading TEM showed inter-contactity of the particles. The dielectric constant (υ') increased with silica loading and reached an optimum at about 10 wt%. The υ' of the nanocomposites showed linear decrease with frequency whereas AC conductivity (σac) increases. The σac and υ' increased marginally with temperature and sea water aging.

  12. Dielectric properties of conductive ionomers

    Science.gov (United States)

    Klein, Robert James

    Ion and polymer dynamics of ion-containing polymers were investigated, with the majority of results obtained from application of a physical model of electrode polarization (EP) to dielectric spectroscopy data. The physical model of MacDonald, further developed by Coelho, was extended for application to tan delta (the ratio of dielectric loss to dielectric constant) as a function of frequency. The validity of this approach was confirmed by plotting the characteristic EP time as a function of thickness and comparing the actual and predicted unrelaxed dielectric constant for a poly(ethylene oxide) (PEO)-based ionomer neutralized by lithium, sodium, and cesium. Results were obtained for ion mobility and mobile ion concentration for a neat PEO-based ionomer, two (methoxyethoxy-ethoxy phosphazene) (MEEP) -based ionomers, two MEEP-based salt-doped polymers, sulfonated polystyrene (SPS) neutralized by sodium with a high sulfonation fraction, and SPS neutralized by zinc with a low sulfonation fraction. Additionally, the conductivity parameters of six plasticized forms of a neat PEO-based ionomer were characterized, but the method apparently failed to correctly evaluate bulk ionic behavior. In all cases except the SPS ionomers ion mobility follows a Vogel-Fulcher-Tammann (VFT) temperature dependence. In all cases, mobile ion concentration follows an Arrhenius temperature dependence. Fitting parameters from these two relationships yielded direct information about the state of ionic diffusion and ion pairing in each system. Combination of these two functionalities predicts a relationship for conductivity that is significantly different than the VFT relation typically used in the literature to fit conductivity. The most outstanding result was the extremely small fraction of ions found to be mobile. For ionomers it can be concluded that the primary reason for low conductivities arises from the low fraction of mobile ions. The local and segmental dynamics of the neat and

  13. Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

    Directory of Open Access Journals (Sweden)

    Narang Sukhleen Bindra

    2015-06-01

    Full Text Available Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST, were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6. X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K to 623 K and frequency range of 10 KHz to 1 MHz. The dielectric constant (εr, loss tangent (tan δ, and AC conductivity (σAC were measured on sintered disks of BST samples. The DC resistivity of different compositions was measured at room temperature. Detailed studies of dielectric and electrical properties showed that these properties are strongly dependent on composition, frequency and temperature. The compounds showed stable behavior in lower temperature range (up to 523 K, therefore, they can be used in practical applications in this temperature range.

  14. Quantitatively analyzing dielectrical properties of resins and mapping permittivity variations in CFRP with high-frequency eddy current device technology

    Science.gov (United States)

    Gäbler, Simone; Heuer, Henning; Heinrich, Gert; Kupke, Richard

    2015-03-01

    Eddy current testing is well-established for non-destructive characterization of electrical conductive materials. The development of high-frequency eddy current technology (with frequency ranges up to 100 MHz) made it even possible to extend the classical fields of application towards less conductive materials like CFRP. Maxwell's equations and recent research show that the use of high-frequency eddy current technology is also suitable for non-conductive materials. In that case the change of complex impedance of the probing coil contains information on sample permittivity. This paper shows that even a quantitative measurement of complex permittivity with high-frequency eddy current device technology is possible using an appropriate calibration. Measurement accuracy is comparable to commercial capacitive dielectric analyzers. If the sample material is electrically conductive, both, permittivity and conductivity influence the complex impedance measured with high-frequency eddy current devices. Depending on the measurement setup and the sheet resistance of the sample a parallel characterization of both parameters is possible on isotropic multi-layer materials. On CFRP the permittivity measurement is much more complex due to the capacitive effects between the carbon rovings. However, first results show that at least the local permittivity variations (like those caused by thermal damages) are detectable.

  15. Titanium dioxide thin films deposited by pulsed laser deposition and integration in radio frequency devices: Study of structure, optical and dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Orlianges, Jean-Christophe, E-mail: jean-christophe.orlianges@unilim.fr [SPCTS, UMR 7315, Universite de Limoges/CNRS, 12 rue Atlantis, 87068 Limoges Cedex (France); Crunteanu, Aurelian; Pothier, Arnaud [XLIM, UMR 7252, Universite de Limoges/CNRS, 123, avenue Albert Thomas, 87060 Limoges Cedex (France); Merle-Mejean, Therese [SPCTS, UMR 7315, Universite de Limoges/CNRS, 12 rue Atlantis, 87068 Limoges Cedex (France); Blondy, Pierre [XLIM, UMR 7252, Universite de Limoges/CNRS, 123, avenue Albert Thomas, 87060 Limoges Cedex (France); Champeaux, Corinne [SPCTS, UMR 7315, Universite de Limoges/CNRS, 12 rue Atlantis, 87068 Limoges Cedex (France)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer We have grown TiO{sub 2} thin films by PLD on c-sapphire substrate with pre-patterned out-plane capacitor structures. Black-Right-Pointing-Pointer Raman and XRD analyses indicate an evolution from 'amorphous' to anatase and rutile phase. Black-Right-Pointing-Pointer Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements. Black-Right-Pointing-Pointer Permittivity measurements reveal high dielectric constant {epsilon}{sub r} = 120 of 600 Degree-Sign C-grown TiO{sub 2} thin films. - Abstract: Titanium dioxide presents a wide range of technological application possibilities due to its dielectric, electrochemical, photocatalytic and optical properties. The three TiO{sub 2} allotropic forms: anatase, rutile and brookite are also interesting, since they exhibit different properties, stabilities and growth modes. For instance, rutile has a high dielectric permittivity, of particular interest for the integration as dielectric in components such as microelectromechanical systems (MEMS) for radio frequency (RF) devices. In this study, titanium dioxide thin films are deposited by pulsed laser deposition. Characterizations by Raman spectroscopy and X-ray diffraction show the evolution of the structural properties. Thin films optical properties are investigated using spectroscopic ellipsometry and transmission measurements from UV to IR range. Co-planar waveguide (CPW) devices are fabricated based on these films. Their performances are measured in the RF domain and compared to simulation, leading to relative permittivity values in the range 30-120, showing the potentialities of the deposited material for capacitive switches applications.

  16. High frequency dielectric properties of Eu{sup +3}-substituted Li–Mg ferrites synthesized by sol–gel auto-combustion method

    Energy Technology Data Exchange (ETDEWEB)

    Asif Iqbal, M., E-mail: asifiqqbal@yahoo.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 Pakistan (Pakistan); Nust College of Electrical and Mechanical Engineering, Islamabad (Pakistan); Islam, M.U., E-mail: muislampk@yahoo.com [Department of Physics, Bahauddin Zakariya University, Multan 60800 Pakistan (Pakistan); Ali, Irshad [Department of Physics, Bahauddin Zakariya University, Multan 60800 Pakistan (Pakistan); Khan, Muhammad Azhar [Department of Physics, Islamia University, Bahawalpur 63100 Pakistan (Pakistan); Sadiq, Imran; Ali, Ihsan [Department of Physics, Bahauddin Zakariya University, Multan 60800 Pakistan (Pakistan)

    2014-02-15

    Graphical abstract: Variation in Cole–Cole plots with frequency for Li{sub 1.2}Mg{sub 0.4}Eu{sub x}Fe{sub (2−x)}O{sub 4} ferrites (x = 0.00,0.02, 0.04, 0.06, 0.08, 0.10). -- Highlights: • The variation in lattice constant is due to partial solubility of Eu-ions into lattice. • The dielectric properties follows Maxwell Weigner model. • Impedance measurements revealed that the impedance response is dominated by grain boundary behavior. • The ac conductivity showed semiconducting behavior over a wide range of frequency. -- Abstract: A series of Li{sub 1.2}Mg{sub 0.4}Eu{sub x}Fe{sub (2−x)}O{sub 4} (x = 0.00, 0.02, 0.04, 0.06, 0.08, 0.10) ferrites is synthesized by sol–gel auto-combustion method. The effect of Europium substitution on dielectric properties of Li–Mg ferrites is reported. XRD analysis reveals fcc phase in all the samples along with few traces of second phase except at x = 0.00 and 0.02. The lattice constant increases initially and then decreases with the substitution of Eu due to partial solubility of Eu-ions in the lattice. The dielectric properties determined in the frequency range 1 MHz-3 GHz followed Maxwell Wagner model. The variation in Cole–Cole plots for different samples correspond to the influence of substituted concentration of Eu{sup 3+} ions.

  17. Dielectric Properties of a New Ceramic System (Mg0.95Zn0.05)2TiO4-CaTiO3 at Microwave Frequencies

    Science.gov (United States)

    Huang, Cheng-Liang; Liu, Shih-Sheng; Chen, Shih-Hsuan

    2009-07-01

    The microwave dielectric properties and microstructure of a two-phase (Mg0.95Zn0.05)2TiO4-CaTiO3 ceramic system prepared using the conventional solid-state route were investigated. The structure and microstructure were analyzed by X-ray diffraction and scanning electron microscopy, respectively. Ilmenite-structured (Mg0.95Zn0.05)TiO3 was detected as a second phase. The coexistence of the second phase, however, did not degrade the dielectric properties of the specimen because the phases were compatible. At 1270 °C, 0.92(Mg0.95Zn0.05)2TiO4-0.08CaTiO3 ceramic showed a good combination of microwave dielectric properties: a dielectric constant (ɛr) of ˜18.03, a quality factor (Q ×f) value of ˜153,000 GHz (at 10 GHz), and a temperature coefficient of resonant frequency (τf) of ˜ -16.82 ppm/°C. The τf value is strongly correlated to the composition and can be controlled by the compositional ratio. At x = 0.1, an ɛr of ˜19.15, a Q ×f value of ˜94,400 GHz (at 10 GHz), and a τf of ˜1.5 ppm/°C were obtained for 0.9(Mg0.95Zn0.05)2TiO4-0.1CaTiO3 ceramic sintered at 1270 °C for 4 h.

  18. Effect of Fungicide Treatment on Dielectric Properties of Few Coarse-Cereals Over the Frequency Range of 0.01 to 10 MHz

    Directory of Open Access Journals (Sweden)

    Vishal Singh CHANDEL

    2012-09-01

    Full Text Available The effect of fungicides’ (thiram, carbendazim, captan, bagalol treatment on the dielectric constant and dielectric loss of a few coarse-cereals seeds, namely the sorghum, maize, barley and pearl millet at given moisture content and bulk densities were examined using Hewlett-Packard (HP-4194A impedance/gain phase analyzer over the frequency range of 0.01 to 10 MHz and temperature range of 30 - 45 °C. Julabo (temperature controller, F-25, Germany was used for keeping the temperature of seeds constant. The study showed that fungicide treatment caused considerable change in the dielectric parameters namely the dielectric constant and dielectric loss. These changes cannot be ignored when precise and accurate determination of dielectric parameters is required for agricultural technology.

  19. Frequency and voltage dependence of electric and dielectric properties of Au/TiO2/n-4H-SiC (metal-insulator-semiconductor) type Schottky barrier diodes

    Science.gov (United States)

    Tanrıkulu, E. E.; Yıldız, D. E.; Günen, A.; Altındal, Ş.

    2015-09-01

    The main electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type Schottky barrier diodes (SBDs) have been investigated as functions of frequency and applied bias voltage. We believe that the use of high dielectric interfacial layer between metal and semiconductor can improve the performance of Schottky diodes. From the experimental data, both electrical and dielectric parameters were found as strong function of frequency and applied bias voltage. The Fermi energy level (EF), the concentration of doping donor atoms (P), barrier height (ΦB) and series resistance (Rs) values were obtained from reverse and forward bias C-V characteristics. The changes in EF and ND with frequency are considerably low. Therefore, their values were taken at about constant. The real and imaginary parts of dielectric constant (\\varepsilon \\prime , \\varepsilon \\prime\\prime ), tangent loss (tanδ), ac electrical conductivity (σac), and real and imaginary parts of electric modulus (M‧ and M″) values were also obtained from reverse and forward bias C-V and G/ω-V characteristics. In addition, the voltage dependent profiles of all these electrical and dielectric parameters were drawn for each frequency. These results confirmed that both electrical and dielectric properties of Au/TiO2/n-4H-SiC (MIS) type SBD are quite sensitive to both the frequency and applied bias voltage due to surface polarization, density distribution of interface traps (Dit), and interfacial layer.

  20. Electric and Dielectric Properties of Au/ZnS-PVA/n-Si (MPS) Structures in the Frequency Range of 10-200 kHz

    Science.gov (United States)

    Baraz, Nalan; Yücedağ, İbrahim; Azizian-Kalandaragh, Yashar; Ersöz, Gülçin; Orak, İkram; Altındal, Şemsettin; Akbari, Bashir; Akbari, Hossein

    2017-07-01

    Pure polyvinyl alcohol (PVA) capped ZnS semiconductor nanocrystals were prepared by microwave-assisted method, and the optical and structural properties of the as-prepared materials were characterized by x-ray diffraction (XRD) and Ultraviolet-visible (UV-Vis) techniques. The XRD pattern shows the formation of ZnS nanocrystals, and the UV-Vis spectroscopy results show a blue shift of about 1.2 eV in its band gap due to the confinement of very small nanostructures. The concentration of donor atoms ( N D), diffusion potential ( V D), Fermi energy level ( E F), and barrier height (ΦB ( C- V)) values were obtained from the reverse bias C -2- V plots for each frequency. The voltage dependent profile of series resistance ( R s) and surface states ( N ss) were also obtained using admittance and low-high frequency methods, respectively. R s- V and N ss- V plots both have distinctive peaks in the depletion region due to the spatial distribution charge at the surface states. The effect of R s and interfacial layer on the C- V and G/ ω- V characteristics was found remarkable at high frequencies. Therefore, the high frequency C- V and G/ ω- V plots were corrected to eliminate the effect of R s. The real and imaginary parts of dielectric constant ( ɛ' and ɛ″) and electric modulus ( M' and M″), loss tangent (tan δ), and ac electrical conductivity ( σ ac) were also obtained using C and G/ ω data and it was found that these parameters are indeed strong functions of frequency and applied bias voltage. Experimental results confirmed that the N ss, R s , and interfacial layer of the MPS structure are important parameters that strongly influence both the electrical and dielectric properties. The low values of N ss ( 109 eV-1 cm-2) and the value of dielectric constant ( ɛ' = 1.3) of ZnS-PVA interfacial layer even at 10 kHz are very suitable for electronic devices when compared with the SiO2. These results confirmed that the ZnS-PVA considerably improves the performance of

  1. Effect of shape of scatterers and plasma frequency on the complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Fathollahi Khalkhali, T., E-mail: tfathollahi@aeoi.org.ir; Bananej, A.

    2016-12-16

    In this study, we analyze complete photonic band gap properties of two-dimensional dielectric-plasma photonic crystals with triangular and square lattices, composed of plasma rods with different geometrical shapes in the anisotropic tellurium background. Using the finite-difference time-domain method we discuss the maximization of the complete photonic band gap width as a function of plasma frequency and plasma rods parameters with different shapes and orientations. The numerical results demonstrate that our proposed structures represent significantly wide complete photonic band gaps in comparison to previously studied dielectric-plasma photonic crystals. - Highlights: • In this paper, we have investigated plasma photonic crystals. • Plasma is a kind of dispersive medium with its equivalent refractive index related to the frequency of an incident EM wave. • In this work, our simulations are performed using the Meep implementation of the finite-difference time-domain (FDTD) method. • For this study, the lattice structures investigated are triangular and square. • Extensive calculations reveal that almost all of these structures represent wide complete band gaps.

  2. Waveguide sensor with metamaterial structure for determination of dielectric properties

    Science.gov (United States)

    Steigmann, R.; Savin, A.; Isteníková, K.; Faktorová, D.; Fabo, P.

    2017-08-01

    Microwave sensor (MWS) compared with classical sensor, offers many advantage such as rapid and nondestructive measurement. At microwave (MW) frequencies, dielectric properties of materials depend on frequency, moisture content, bulk density and temperature. MW waveguide sensors can measure properties of materials based on MW interaction with matter, and provide information about dielectric properties of investigated dielectric material, characterized with complex permittivity. The paper presents a new approach for determination of the dielectric properties of dielectric material by embedding a metamaterial (MM) structure over the aperture of waveguide sensor in order to increase the sensing properties of classical waveguide sensor. The optimal design of MM structure for waveguide sensor tuning in MW X-band is obtained. In this new approach the MM function in two ways: like a tool for increasing the sensibility of classical waveguide sensor and the tool sensitive to the dielectric properties of investigated material through the adjusted resonance frequency of designed MM units. The numerical simulation of 2D MM structure properties and experimental results for dielectric properties of dielectric materials are carried out.

  3. Novel photoswitchable dielectric properties on nanomaterials of electronic core-shell γ-FeOx@Au@fullerosomes for GHz frequency applications

    Science.gov (United States)

    Wang, Min; Su, Chefu; Yu, Tzuyang; Tan, Loon-Seng; Hu, Bin; Urbas, Augustine; Chiang, Long Y.

    2016-03-01

    We unexpectedly observed a large amplification of the dielectric properties associated with the photoswitching effect and the new unusual phenomenon of delayed photoinduced capacitor-like (i.e. electric polarization) behavior at the interface on samples of three-layered core-shell (γ-FeOx@AuNP)@[C60(>DPAF-C9)]n2 nanoparticles (NPs) in frequencies of 0.5-4.0 GHz. The detected relative dielectric constant amplification was initiated upon switching off the light followed by relaxation to give an excellent recyclability. These NPs having e--polarizable fullerosomic structures located at the outer layer were fabricated from highly magnetic core-shell γ-FeOx@AuNPs. Surface-stabilized 2 in a core-shell structure was found to be capable of photoinducing the surface plasmonic resonance (SPR) effect by white LED light. The accumulated SPR energy was subsequently transferred to the partially bilayered C60(>DPAF-C9) fullerosomic membrane layer in a near-field (~1.5 nm) region without producing radiation heat. Since the monostatic SAR signal is dielectric property-dependent, we used these measurements to provide evidence of derived reflectivity changes on a surface coated with 2 at 0.5-4.0 GHz upon illumination of LED white light. We found that a high, >99%, efficiency of response amplification in image amplitude can be achieved.We unexpectedly observed a large amplification of the dielectric properties associated with the photoswitching effect and the new unusual phenomenon of delayed photoinduced capacitor-like (i.e. electric polarization) behavior at the interface on samples of three-layered core-shell (γ-FeOx@AuNP)@[C60(>DPAF-C9)]n2 nanoparticles (NPs) in frequencies of 0.5-4.0 GHz. The detected relative dielectric constant amplification was initiated upon switching off the light followed by relaxation to give an excellent recyclability. These NPs having e--polarizable fullerosomic structures located at the outer layer were fabricated from highly magnetic core-shell

  4. Microstructural and dielectric susceptibility effects on predictions of dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    Ferris, K.F.; Exarhos, G.J. [Pacific Northwest National Lab., Richland, WA (United States); Risser, S.M. [Texas A& M Univ., Commerce, TX (United States)

    1997-12-01

    In modeling the dielectric properties of inhomogeneous materials, the treatment of the electric field interactions differentiate the usual modeling formalisms (such as the Maxwell-Garnett and Bruggeman effective medium methods) and their accuracy. In this paper, we show that the performance of effective medium methods is dependent upon a number of variables - defect concentration, alignment, and the dielectric constant of the material itself. Using our previously developed finite element model of an inhomogeneous dielectric, we have developed models for a number of dielectric films of varying dielectric constant and microstructures. Alignment of defects parallel to the applied field and the larger defect aspect ratios increase the overall dielectric constant. The extent of these effects is dependent on the dielectric constant of the bulk component.

  5. Dielectric Properties of Flocculated Water-in-Oil Emulsions

    Energy Technology Data Exchange (ETDEWEB)

    Skodvin, T.

    1995-12-31

    When an offshore oil field is near completion, water occupies a large fraction of the available pore volume. Thus, in collecting the oil and gas reserves, one has to deal with a high co-production of either formation- or injected water. This doctoral thesis focuses on the effect of water-in-oil emulsions on the dielectric properties, in particular the effect of flocculation. Various dielectric models are applied to obtain methods for qualitative and quantitative characterization of the flocculated state. Permittivity and measurement of dielectric properties are discussed as a basis for the interpretation of the dielectric properties of the emulsions. Various flocculation models are presented. It is concluded that the dielectric properties of water-in-oil emulsions are strongly influenced by continuously ongoing processes in the system. Because of flocculation and sedimentation the traditional dielectric mixture models cannot satisfactorily predict the dielectric behaviour. The experimentally obtained permittivities for the emulsions can be reproduced by including flocculation in the models and treating the floc aggregates as spheroids or subsystems with dielectric properties given by the degree of flocculation. The models discussed have difficulties reproducing the complete frequency behaviour found experimentally. This is probably because the dielectric relaxation may be influenced by processes not included in the models, such as the effects of dipolar or multipolar interactions between the droplets. For further research it is recommended that rheological and dielectric measurements be combined. 227 refs., 61 figs., 16 tabs.

  6. Dielectric properties of Al-substituted Co ferrite nanoparticles

    Indian Academy of Sciences (India)

    A T Raghavender; K M Jadhav

    2009-12-01

    A series of polycrystalline spinel ferrites with composition, CoFe2–AlO4 (0 ≤ ≤ 1), have been synthesized by sol–gel method. The effect of Al-substitution on structural and dielectric properties is reported in this paper. X-ray diffraction analysis revealed the nanocrystalline nature in the prepared ferrite samples. The particle size, , decreases with increase in Al-content. The lattice parameter, and X-ray density, x, decreased with increase in Al-content. The dielectric properties for all the samples have been studied as a function of frequency in the range 100 Hz–10 MHz. Dielectric properties such as dielectric constant, ′, dielectric loss, ″ and dielectric loss tangent, tan , have been studied for nanocrystalline ferrite samples as a function of frequency. The dielectric constant and dielectric loss obtained for the nanocrystalline ferrites proposed by this technique possess lower value than that of the ferrites prepared by other methods for the same composition. The low dielectric behaviour makes ferrite materials useful in high frequency applications.

  7. Characteristics of radio-frequency atmospheric pressure dielectric-barrier discharge with dielectric electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, S., E-mail: shussain@uos.edu.pk, E-mail: shussainuos@yahoo.com; Qazi, H. I. A.; Badar, M. A. [Department of Physics, University of Sargodha, 40100 Sargodha (Pakistan)

    2014-03-15

    An experimental investigation to characterize the properties and highlight the benefits of atmospheric pressure radio-frequency dielectric-barrier discharge (rf DBD) with dielectric electrodes fabricated by anodizing aluminium substrate is presented. The current-voltage characteristics and millisecond images are used to distinguish the α and γ modes. This atmospheric rf DBD is observed to retain the discharge volume without constriction in γ mode. Optical emission spectroscopy demonstrates that the large discharge current leads to more abundant reactive species in this plasma source.

  8. Dielectric properties of Ni substituted Li-Zn ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Soibam, Ibetombi, E-mail: ibetombi_phys@rediffmail.co [Department of Physics, Manipur University, Canchipur, Manipur 795 003 (India); Phanjoubam, Sumitra [Department of Physics, Manipur University, Canchipur, Manipur 795 003 (India); Radhapiyari, L. [Solid State Physics Laboratory, Lucknow Road, New Delhi 110 054 (India)

    2010-05-01

    Li{sub 0.4-0.5x}Zn{sub 0.2}Ni{sub x} Fe{sub 2.4-0.5x}O{sub 4} ferrites with x varying from 0.02 to 0.1 in steps of 0.02 have been synthesized by the citrate precursor method and investigated for their dielectric properties. A decrease in the value of room temperature dielectric constant is observed with the increase in Ni concentration. It has been explained in terms of space charge polarization and Koop's two layer model. The variation in dielectric constant with frequency shows dispersion while a resonance peak could be seen in the variation of dielectric loss with frequency. With increase in temperature the dielectric constant and dielectric loss increased, which have been discussed in terms of polarization and the Debye-type of dispersion. Possible mechanism contributing to the above process is discussed.

  9. THE HIGH-FREQUENCY DIELECTRIC PROPERTIES OF PMI FOAM AND SANDWICH STRUCTURES%PMI泡沫塑料及其夹层结构的高频介电性能研究

    Institute of Scientific and Technical Information of China (English)

    张乐; 张广成

    2013-01-01

    The influence of density and thickness of PMI foam on its high-frequency dielectric properties and its sandwich structures with carbon fiber or glass fiber at 10GHz was studied.The results indicate that the thickness of the PMI foam has little effect on the high-frequency dielectric properties.The high-frequency dielectric properties increased linearly with the increase of the foam density,which was consistent with the theoretically calculated values.The high-frequency dielectric properties of sandwich structures gradually thickened with the increase of the foam thickness,which was close to that of PMI foam gradually,and the law conforms to the series formula model.The high-frequency dielectric properties of glass-fiber sandwich structures was less than the carbon-fiber sandwich structures.%本文研究了密度和厚度对PMI泡沫塑料及其碳纤维、玻璃纤维夹层结构10GHz的高频介电性能的影响.结果表明,PMI泡沫塑料的厚度对其高频介电性能影响不大;随着密度的增加,PMI泡沫塑料的高频介电性能呈近线性规律增大,并与理论计算值基本一致;随着厚度的增加,其碳纤维夹层结构和玻璃纤维夹层结构的高频介电性能均不断降低,并逐渐接近纯PMI泡沫塑料的介电性能,其规律符合串联公式模型;玻璃纤维夹层结构的高频介电性能低于碳纤维夹层结构.

  10. Dielectric properties of human placenta, umbilical cord and amniotic fluid

    Energy Technology Data Exchange (ETDEWEB)

    Peyman, A [Physical Dosimetry Department, Health Protection Agency, Chilton, Didcot OX11 0RQ (United Kingdom); Gabriel, C [MCL-P, Newbury RG14 5PY, Berkshire (United Kingdom); Benedickter, H R; Froehlich, J, E-mail: Azadeh.peyman@hpa.org.uk [Electromagnetic Fields and Microwave Electronics Laboratory, Swiss Federal Institute of Technology, Zurich (Switzerland)

    2011-04-07

    The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 deg. C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields. (note)

  11. Dielectric properties of human placenta, umbilical cord and amniotic fluid

    Science.gov (United States)

    Peyman, A.; Gabriel, C.; Benedickter, H. R.; Fröhlich, J.

    2011-04-01

    The dielectric properties of freshly delivered human placenta, umbilical cord and amniotic fluid have been acquired at 37 °C and in the frequency range of 200 MHz-10 GHz. The experimental data were fitted to a Cole-Cole expression. The results show that dielectric properties of the umbilical cord are significantly higher than placenta due to the presence of high water content Wharton's jelly. The results also demonstrate large differences in the dielectric properties of amniotic and cerebrospinal fluids. The data presented can be used in numerical simulations of the exposure of pregnant women to electromagnetic fields.

  12. Dielectric studies of wheat in powder form at microwave frequencies.

    Science.gov (United States)

    Sharma, Kavita; Jain, Ritu; Bhargava, Nidhi; Sharma, Ritu; Sharma, K S

    2010-10-01

    Dielectric constant and loss factor of Raj-4120 variety of Indian wheat were determined in powder form (grain size 125 to 150 micron) at room temperature. Microwaves at three different frequencies were employed in C-band, X-band and Ku-band respectively for investigating frequency dependence of dielectric parameters of the sample. Bulk dielectric values of the sample were determined by employing the dielectric mixture relations, such as, half power mixture equation, Landau and Lifshitz, Looyenga equation etc.

  13. Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

    Science.gov (United States)

    Taşçıoğlu, İ.; Tüzün Özmen, Ö.; Şağban, H. M.; Yağlıoğlu, E.; Altındal, Ş.

    2017-04-01

    In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements in the frequency range of 10 kHz-2 MHz. The C- V- f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states ( N ss). The values of N ss located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant ( ɛ') and dielectric loss ( ɛ″) decrease with increasing frequency, whereas loss tangent (tan δ) remains nearly the same. The decrease in ɛ' and ɛ″ was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity ( σ ac) and electric modulus ( M' and M″) increase with increasing frequency.

  14. Dielectric properties of porcine glands, gonads and body fluids.

    Science.gov (United States)

    Peyman, A; Gabriel, C

    2012-10-01

    Dielectric properties of porcine glandular tissues and gonads (in vivo) and body fluids (in vitro) have been obtained in the frequency range of 50 MHz to 20 GHz. The experimental data were fitted to a two term Cole-Cole expression. The data presented complement the available dielectric properties of tissues in the literature and can be used in numerical simulations of the exposure of people to electromagnetic fields.

  15. Effect of Gadolinium Substitution on Dielectric Properties of Bismuth Ferrite

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Multiferroic Bi1-xGdxFeO3(x=0, 0.05, 0.1, 0.15, 0.2) ceramics were prepared by conventional solid state reaction method. X-ray diffraction was carried out to characterize the crystal structure and to detect any possible impurities existing in these ceramics. Frequency dependence of dielectric properties of Bi1-xGdxFeO3 samples at room temperature was measured in a frequency range from 100 Hz to 1 MHz using an HP4294A precision impedance analyzer. For all the samples studied, the dielectric constant and dielectric loss decreases with increasing frequency in the range between 100 Hz and 1 MHz, as can be expected from a typical orientational dielectric relaxation process. There is no indication of any dips over the whole frequency range studied, which is in direct contrast with that reported previously. It is found that both dielectric constant and dielectric loss are strongly dependent on the Gd3+ content. The effect of introducing Gd3+ is to increase the dielectric constant and to decrease the dielectric loss for slightly doped sample Bi0.95Gd0.05FeO3: the dielectric constant of the sample at 1 kHz reaches 600, six times bigger than that for pure BiFeO3. Complicated dielectric behaviors are observed at higher doping levels. Furthermore, the substitution of rare earth Gd for Bi helps to eliminate the impurity phase in BiFeO3 ceramics. There is strong evidence that both lattice constants a and c of the unit cell become smaller as the Gd3+ content is increased. The dielectric constant and loss and their frequency responses can be varied dramatically by substitution of Gd.

  16. Dielectric measurements on PWB materials at microwave frequencies

    Indian Academy of Sciences (India)

    A Tanwar; K K Gupta; P J Singh; Y K Vijay

    2006-04-01

    In quest of finding new substrate for printed wiring board (PWB) having low dielectric constant, we have made PSF/PMMA blends and evaluated the dielectric parameters at 8.92 GHz frequency and at 35°C temperature. Incorporating PMMA in PSF matrix results in reduced dielectric constant than that of pure PSF. The dielectric parameters of pure PMMA and PSF films of different thicknesses have also been obtained at microwave frequencies. We have used dielectric data at microwave frequencies as a tool to evaluate optical constants, absorption index `’ and refractive index `’. The blends of PSF/PMMA may be used as base materials for PWBs.

  17. Structural, ac conductivity and dielectric properties of 3-formyl chromone

    Science.gov (United States)

    Ali, H. A. M.

    2017-07-01

    The structure for the powder of 3-formyl chromone was examined by X-ray diffraction technique in the 2θ° range ( 4° - 60° . The configuration of Al/3-formyl chromone/Al samples was designed. The electrical and dielectric properties were studied as a function of frequency (42- 5 × 106 Hz) and temperature (298-408K). The ac conductivity data of bulk of 3-formyl chromone varies as a power law with the frequency at different temperatures. The predominant mechanism for ac conduction was deduced. The ac conductivity shows a thermally activated process at different frequencies. The dielectric constant and dielectric loss were determined using the capacitance and dissipation factor measurements at different temperatures. The dielectric loss shows a peak of relaxation time that shifted to higher frequency with an increase in the temperature. The activation energy of the relaxation process was estimated.

  18. The dielectric properties of human pineal gland tissue and RF absorption due to wireless communication devices in the frequency range 400-1850 MHz

    Energy Technology Data Exchange (ETDEWEB)

    Schmid, Gernot [Austrian Research Centers GmbH-ARC, ITM, A-2444 Seibersdorf (Austria); Ueberbacher, Richard [Austrian Research Centers GmbH-ARC, ITM, A-2444 Seibersdorf (Austria); Samaras, Theodoros [Department of Physics, Aristotle University of Thessaloniki, GR-54124 Thessaloniki (Greece); Tschabitscher, Manfred [Center of Anatomy and Cell Biology, Medical University of Vienna, A-1090 Vienna (Austria); Mazal, Peter R [Department of Clinical Pathology, Medical University Vienna, A-1090 Vienna (Austria)

    2007-09-07

    In order to enable a detailed analysis of radio frequency (RF) absorption in the human pineal gland, the dielectric properties of a sample of 20 freshly removed pineal glands were measured less than 20 h after death. Furthermore, a corresponding high resolution numerical model of the brain region surrounding the pineal gland was developed, based on a real human tissue sample. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-1850 MHz were carried out. For typical output power values of real handheld mobile communication devices, the obtained results showed only very small amounts of absorbed RF power in the pineal gland when compared to SAR limits according to international safety standards. The highest absorption was found for the 400 MHz irradiation. In this case the RF power absorbed inside the pineal gland (organ mass 96 mg) was as low as 11 {mu}W, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power in the pineal gland were found to be lower by a factor of 4.2 and 36, respectively. These results indicate that temperature-related biologically relevant effects on the pineal gland induced by the RF emissions of typical handheld mobile communication devices are unlikely.

  19. Millimeter wave and terahertz dielectric properties of biological materials

    Science.gov (United States)

    Khan, Usman Ansar

    Broadband dielectric properties of materials can be employed to identify, detect, and characterize materials through their unique spectral signatures. In this study, millimeter wave, submillimeter wave, and terahertz dielectric properties of biological substances inclusive of liquids, solids, and powders were obtained using Dispersive Fourier Transform Spectroscopy (DFTS). Two broadband polarizing interferometers were constructed to test materials from 60 GHz to 1.2 THz. This is an extremely difficult portion of the frequency spectrum to obtain a material's dielectric properties since neither optical nor microwave-based techniques provide accurate data. The dielectric characteristics of liquids such as cyclohexane, chlorobenzene, benzene, ethanol, methanol, 1,4 dioxane, and 10% formalin were obtained using the liquid interferometer. Subsequently the solid interferometer was utilized to determine the dielectric properties of human breast tissues, which are fixed and preserved in 10% formalin. This joint collaboration with the Tufts New England Medical Center demonstrated a significant difference between the dielectric response of tumorous and non-tumorous breast tissues across the spectrum. Powders such as anthrax, flour, talc, corn starch, dry milk, and baking soda have been involved in a number of security threats and false alarms around the globe in the last decade. To be able to differentiate hoax attacks and serious security threats, the dielectric properties of common household powders were also examined using the solid interferometer to identify the powders' unique resonance peaks. A new sample preparation kit was designed to test the powder specimens. It was anticipated that millimeter wave and terahertz dielectric characterization will enable one to clearly distinguish one powder from the other; however most of the powders had relatively close dielectric responses and only Talc had a resonance signature recorded at 1.135 THz. Furthermore, due to

  20. Microwave dielectric properties of horticultural peat products

    Directory of Open Access Journals (Sweden)

    G. Ayalew

    2007-04-01

    Full Text Available The microwave dielectric properties of horticultural peat and compost peat were measured with a HP85107C network analyser in conjunction with a HP85070B open-ended coaxial dielectric probe for the frequency range 0.5–20 GHz. Loose samples had volumetric water contents ranging from 0.11 to 0.24 Mg m-3. For analysis, samples were compressed to 1.0× (no compression, 1.2×, 1.5× and 2.0× original bulk density, giving volumetric water contents ranging from 0.11 to 0.48 Mg m-3. The raw relative permittivity data exhibited a high degree of variability, but rank-based removal of outlier measurements helped to improve their coherence with volumetric water content. The difference between horticultural peat and compost peat was insignificant in terms of both the dielectric constant and the loss factor. The results suggest that relative permittivity data after the removal of outliers can be of sufficiently high quality for sensing applications in the horticultural peat industry such as dedicated water content monitoring, nutrient management, and foreign body detection systems for health and safety purposes, given the low-precision requirements that are appropriate for horticultural and compost peat as high-volume, low-value and non-critical commodities.

  1. Dielectric and photo-dielectric properties of TlGaSeS crystals

    Indian Academy of Sciences (India)

    A F Qasrawi; Samah F Abu-Zaid; Salam A Ghanameh; N M Gasanly

    2014-05-01

    The room temperature, dark and photo-dielectric properties of the novel crystals TlGaSeS are investigated in the frequency, intensity and biasing voltage having ranges of ~ 1–120 MHz, 14–40 klux and 0–1 V, respectively. The crystals are observed to exhibit a dark high frequency effective dielectric constant value of ∼ 10.65 × 103 with a quality factor of ∼ 8.84 × 104 at ∼ 120 MHz. The dielectric spectra showed sharp resonance–antiresonance peaks in the frequency range of ∼ 25–250 kHz. When photoexcited, pronounced increase in the dielectric constant and in the quality factor values with increasing illumination intensity are observed. Signal amplification up to ∼ 33% with improved signal quality up to ∼ 29% is attainable via photoexcitation. On the other hand, the illuminated capacitance–voltage characteristics of the crystals reflected a downward shift in the voltage biasing and in the built-in voltage of the device that is associated with increase in the uncompensated carrier density. The increase in the dielectric constant with increasing illumination intensity is ascribed to the decrease in the crystal's resistance as a result of increased free carrier density. The light sensitivity of the crystals, the improved dielectric properties and the lower biasing voltage obtained via photoexcitation and the well-enhanced signal quality factor of the crystals make them promising candidates for optical communication systems.

  2. Dielectric properties of grain–grainboundary binary system

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Peng-Fei, E-mail: pfcheng@xpu.edu.cn [School of Science, Xi’an Polytechnic University, Xi’an 710048 (China); Li, Sheng-Tao; Wang, Hui [State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China)

    2014-09-15

    Dielectric properties of grain–grainboundary binary system are analyzed theoretically and compared with unary system and classical Maxwell–Wagner (MW) polarization in binary system. It is found that MW polarization appears at higher frequency compared with intrinsic polarization for grain–grainboundary binary system, which is abnormal compared with classical dielectric theory. This dielectric anomaly is premised on the existence of electronic relaxation at grainboundary. The origin of giant dielectric constant of CaCu{sub 3}Ti{sub 4}O{sub 12} (CCTO) ceramics is also investigated on the basis of the theoretical results. It is proposed that low frequency relaxation originates from electronic relaxation of oxygen vacancy at depletion layer, while high frequency relaxation comes from MW polarization. The results of this paper offer a quantitative identification of MW polarization from intrinsic polarization at grainboundary and a judgment of the mechanism and location of a certain polarization in grain–grainboundary binary system.

  3. Influence of temperature and frequency on the AC conductivity and dielectric properties for Ge{sub 15}Se{sub 60}Bi{sub 25} amorphous films

    Energy Technology Data Exchange (ETDEWEB)

    Atyia, H.E., E-mail: hebaelghrip@hotmail.com; Hegab, N.A.; Affi, M.A.; Ismail, M.I.

    2013-10-15

    Highlights: •σ{sub ac}(ω) obeyed the Aω{sup s} law, s is the frequency exponent decreases with increasing temperature. •σ{sub ac}(ω) increases with increasing temperature, with two slopes which suggests two different regimes σ{sub f}, σ{sub s.} •The dielectric constant ε{sub 1} and dielectric loss ε{sub 2} increase with temperature and decrease with frequency. •Value of the maximum barrierheight W{sub m} is in good agreement with the theory of hopping. -- Abstract: Thin films of Ge{sub 15}Se{sub 60}Bi{sub 25} are prepared by thermal evaporation technique on to well cleaned glass substrates. The film thicknesses are measured by quartz crystal monitor method. Thin film capacitors of the type (Al–Ge{sub 15}Se{sub 60}Bi{sub 25}–Al) have been fabricated. The films were well characterized by X-ray diffraction, differential thermal analysis and energy dispersive X-ray spectroscopy. AC conduction and dielectric studies performed on a stabilized samples of thickness range (89.3–214.3 nm) at various frequencies (10{sup 2}–10{sup 5} Hz) and temperatures (303–413 K). From the AC conduction studies, it is confirmed that the mechanism responsible for the conduction process is hopping. The variations of the dielectric constant and loss as function of frequency and temperature are observed and the results are discussed. Finally, the maximum barrier height W{sub m} and the density of states N(E{sub F}) were determined.

  4. Optimization of structural and dielectric properties of CdSe loaded poly(diallyl dimethyl ammonium chloride) polymer in a desired frequency and temperature window

    Energy Technology Data Exchange (ETDEWEB)

    Tyagi, Chetna, E-mail: ctyagi05@gmail.com; Sharma, Ambika, E-mail: ambikasharma2004@yahoo.com [Department of Applied Sciences, The NorthCap University (Formerly ITM University), Gurgaon, 122017 Haryana (India)

    2016-01-07

    In the present paper, investigations of CdSe loaded poly(diallyl dimethyl ammonium chloride) (PDADMAC) nanocomposites and pure PDADMAC synthesized by wet chemical technique have been carried out. Fourier transform infrared and X-ray diffraction analysis have been performed to reveal the structural details of pure polymer and polymer nanocomposite (PNC). The dielectric behavior of pure polymer and PNC has been recorded, which results in higher value of the real and imaginary part of dielectric constant for PNC, as compared with pure PDADMAC. The increase is attributed to the addition of CdSe quantum dots to the pure polymer. The contribution of ionic and electronic polarization has been observed at higher frequency. The theoretical fitting of Cole-Cole function to the experimental data of dielectric constant of PNC and pure PDADMAC results in the determination of relaxation time and conductivity of space charge carriers. The CdSe loaded polymer nanocomposite has been used as an electrolyte in the battery fabrication with configuration Al/PNC/Ag{sub 2}O. The ac conductivity measurements have been carried out for both samples in a frequency window of 1 kHz–5 MHz and at different temperatures varying from 298 K to 523 K. Activation energy (E{sub a}) has been determined for pure polymer as well as PNC and is found to be less for PNC, as compared with pure polymer. Further, impedance measurement at different temperatures results in two frequency ranges corresponding to ionic conduction and blocking electrode effect. The value of bulk resistance for pure polymer and PNC has been found to be 3660 Ω and 442 Ω, respectively, at 298 K temperature. Electric modulus has been determined and is observed to support the dielectric constant data; it further reveals the deviation from Debye behavior at a higher frequency.

  5. Effect of Gd3+ doping on structural, optical and frequency-dependent dielectric response properties of pseudo-cubic BaTiO3 nanostructures

    Science.gov (United States)

    Borah, Manjit; Mohanta, Dambarudhar

    2014-06-01

    We report on the structural, optical and dielectric characterization of solid state derived, pseudo-cubic nanoscale barium titanates (BTs) with gadolinium (Gd3+) as substitutional dopant. Referring to X-ray diffractograms, apart from the BT peaks related to perovskite structure, the non-existence of any additional peaks due to byproducts has revealed that Gd3+ has undergone substitutional doping into the BT host lattice. The well-separated BT nanoparticles of typical size ˜10-15 nm were observed through electron microscopy studies. Following a direct, allowed type carrier transition ( n=1/2), a reduction in the optical band gap value (from 3.28 to 3.255 eV) was observed when the Gd-doping level was varied within 0-7 %. Conversely, the Urbach energy followed an increasing trend, from a value of 0.741 to 1.879 eV. Furthermore, the dielectric constant showed a decreasing tendency with doping content and with increasing frequency. However, in the low-frequency region, the loss tangent (tan δ), which is the combined result of orientational polarization and electrical conduction, was found to be quite high in the doped samples as compared to their un-doped counterpart. The frequency-dependent electrical data were also analyzed in the framework of conductivity and impedance formalisms. In particular, the ac conductivity which varies as ˜ ω s approaches ideal Debye behavior ( s→1) for a low Gd level and a higher doping concentration did not show improved dielectric feature of the host. The incorporation of rare-earth (Gd3+) ions into the BT host system could greatly manifest dielectric relaxation and carrier conduction mechanisms, in a given frequency range, and thus can find immense scope in miniaturized nanoelectronic elements including ceramic capacitors and transducers.

  6. Optimization of structural and dielectric properties of CdSe loaded poly(diallyl dimethyl ammonium chloride) polymer in a desired frequency and temperature window

    Science.gov (United States)

    Tyagi, Chetna; Sharma, Ambika

    2016-01-01

    In the present paper, investigations of CdSe loaded poly(diallyl dimethyl ammonium chloride) (PDADMAC) nanocomposites and pure PDADMAC synthesized by wet chemical technique have been carried out. Fourier transform infrared and X-ray diffraction analysis have been performed to reveal the structural details of pure polymer and polymer nanocomposite (PNC). The dielectric behavior of pure polymer and PNC has been recorded, which results in higher value of the real and imaginary part of dielectric constant for PNC, as compared with pure PDADMAC. The increase is attributed to the addition of CdSe quantum dots to the pure polymer. The contribution of ionic and electronic polarization has been observed at higher frequency. The theoretical fitting of Cole-Cole function to the experimental data of dielectric constant of PNC and pure PDADMAC results in the determination of relaxation time and conductivity of space charge carriers. The CdSe loaded polymer nanocomposite has been used as an electrolyte in the battery fabrication with configuration Al/PNC/Ag2O. The ac conductivity measurements have been carried out for both samples in a frequency window of 1 kHz-5 MHz and at different temperatures varying from 298 K to 523 K. Activation energy (Ea) has been determined for pure polymer as well as PNC and is found to be less for PNC, as compared with pure polymer. Further, impedance measurement at different temperatures results in two frequency ranges corresponding to ionic conduction and blocking electrode effect. The value of bulk resistance for pure polymer and PNC has been found to be 3660 Ω and 442 Ω, respectively, at 298 K temperature. Electric modulus has been determined and is observed to support the dielectric constant data; it further reveals the deviation from Debye behavior at a higher frequency.

  7. Dense and half-dense NiZnCo ferrite ceramics: Their respective relevance for antenna downsizing, according to their dielectric and magnetic properties at microwave frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Mattei, J.-L., E-mail: mattei@univ-brest.fr; Chevalier, A. [Lab-STICC, Université de Bretagne Occidentale, CS 93837, 6 Avenue Le Gorgeu, 29238 Brest Cedex 3 (France); Le Guen, E. [Lab-STICC, Université de Bretagne Occidentale, CS 93837, 6 Avenue Le Gorgeu, 29238 Brest Cedex 3 (France); IETR, Université de Rennes 1, 263 Avenue General Leclerc, 35042 Rennes Cedex (France)

    2015-02-28

    Spinel ferrite Ni{sub 0.5}Zn{sub 0.3}Co{sub 0.2}Fe{sub 1.98}O{sub 4−x} nanoparticles were synthesized by co-precipitation method, and samples were realized by moulding and annealing at key temperatures (T{sub M} = 800 °C, 900 °C, 1050 °C, determined beforehand through shrinkage measurements) going with calcining and sintering processes. Annealing at 800 °C and 900 °C led to half-dense ceramics (porosity ∼50 vol. %), whereas bulky ferrite was obtained after annealing at 1050 °C. Elemental analysis, X-ray diffraction and ion chromatography analysis were performed. Complex dielectric permittivity (ε*) and magnetic permeability (μ*) were investigated up to 6 GHz. With increasing T{sub M}, a decreasing amount of Fe{sup 2+} was observed, going with increasing sample density. Coupled effects of the Fe{sup 2+} concentration and of the porosity, both on dielectric and magnetic properties, were chiefly investigated and discussed. The materials show almost constant permittivities (ε′ = 5.0, 6.0, and 14.8 for T{sub M} = 800 °C, 900 °C and 1050 °C, respectively). The bulk value at f = 1 GHz (ε′ = 14.8) can be interpreted well according to Shannon's theory. The permittivities of the half-dense ceramics are discussed on the basis of Bruggeman's Effective Medium Theory. The materials annealed at 800 °C and 900 °C show almost constant magnetic permeabilities in the frequency range from 0.2 to 1 GHz (μ′ = 3.4 and 6.0 for T{sub M} = 800 °C and 900 °C). The observed permeability behavior is typical of monodomain particles, except for the sample annealed at 1050 °C, for which domain wall contribution to μ* is suspected because of non-negligible losses at low frequency (μ″ = 1.3–1.8 at f < 0.3 GHz). This finding is supported by estimations of the upper and lower values for the critical grain size, on the basis of Brown–Van der Zaag's theory. Facing bulk ceramics

  8. Dielectric Properties of Nanosized ZnFe2O4

    Directory of Open Access Journals (Sweden)

    Željka Cvejić

    2008-06-01

    Full Text Available In this paper we present the results concerning the dielectric properties of the nanosized ZnFe2O4. Dielectric permittivity, the loss factor, as well as the conductivity, were measured in the temperature range 300-630 K and at 1 Hz, 10 Hz, 100 Hz, 1 kHz and 10 kHz frequencies. Signifi cant improvements in permittivity, loss factor and ionic conductivity comparing to bulk samples have been observed.

  9. Dielectric properties of electrospun titanium compound/polymer composite nanofibres

    Science.gov (United States)

    Li, Meng-Meng; Long, Yun-Ze; Tan, Jin-Shan; Yin, Hong-Xing; Sui, Wan-Mei; Zhang, Zhi-Ming

    2010-02-01

    Poly(vinylpyrrolidone)/tetrabutyl titanate (PVP/ [CH3(CH2)3O]4Ti) composite nanofibres are prepared by electrospinning. After calcining parts of composite nanofibres in air at 700 °C, petal-like TiO2 nanostructures are obtained. The characterizations of composite nanofibres and TiO2 nanostructures are carried out by a scanning electron microscope, an x-ray diffractometer, and an infrared spectrometer. Electrospun nanofibres are pressed into pellets under different pressures in order to explore their dielectric properties. It is found that the dielectric constants decrease with frequency increasing. The dielectric constant of the composite nanofibre pellet increases whereas its dielectric loss tangent decreases due to the doped titanium ions compared with those of pure PVP nanofibre pellets. In addition, it is observed that the dielectric constant of the composite nanofibre pellet decreases with the increase of the pressure applied in pelletization.

  10. Simulated Analysis of Dielectric Properties of Heterogeneous Materials

    Directory of Open Access Journals (Sweden)

    Yang Biao

    2016-01-01

    Full Text Available The present paper reports the results of a numerical analysis of two phases lossless heterogeneous materials based on a three dimensional (3-D random dielectric mixture. The effective permittivity of a 3-D dielectric materials is calculated by the S-parameter retrieval method and finite element method. The calculated effective permittivity is in good agreement with theoretical models by compared with Bruggeman formula and Coherent potential formula, showing that the volume fraction of inclusions is increasing, the effective permittivity increases with radiation frequency and appear an imaginary part taking on the dielectric loss properties.

  11. Frequency Dependence of Attenuation Constant of Dielectric Materials

    Directory of Open Access Journals (Sweden)

    A. S. Zadgaonkar

    1975-01-01

    Full Text Available Different dielectric materials have been studied for frequency dependence of attenuation constant. The sensitive cathode ray oscillograph method has been used to evaluate to the dielectric constant and loss factor, and from these attenuation constants have been calculated. The temperature remaining constant, a regular increase has been observed in attenuation constant, at higher frequencies of electro-magnetic propagating wave.

  12. Mechanisms Responsible for Microwave Properties in High Performance Dielectric Materials

    Science.gov (United States)

    Zhang, Shengke

    Microwave properties of low-loss commercial dielectric materials are optimized by adding transition-metal dopants or alloying agents (i.e. Ni, Co, Mn) to tune the temperature coefficient of resonant frequency (tau f) to zero. This occurs as a result of the temperature dependence of dielectric constant offsetting the thermal expansion. At cryogenic temperatures, the microwave loss in these dielectric materials is dominated by electron paramagnetic resonance (EPR) loss, which results from the spin-excitations of d-shell electron spins in exchange-coupled clusters. We show that the origin of the observed magnetically-induced shifts in the dielectric resonator frequency originates from the same mechanism, as described by the Kramers-Kronig relations. The temperature coefficient of resonator frequency, tauf, is related to three material parameters according to the equation, tau f = - (½ tauepsilon + ½ taumu + alphaL), where tauepsilon, taumu , and alphaL are the temperature coefficient of dielectric constant, magnetic permeability, and lattice constant, respectively. Each of these parameters for dielectric materials of interest are measured experimentally. These results, in combination with density functional simulations, developed a much improved understanding of the fundamental mechanisms responsible for tau f. The same experimental methods have been used to characterize in-situ the physical nature and concentration of performance-degrading point defects in the dielectrics of superconducting planar microwave resonators.

  13. Modelling dielectric and magnetic properties of ferroconcrete

    Directory of Open Access Journals (Sweden)

    T. Frenzel

    2008-05-01

    Full Text Available This contribution discusses the modelling and parameterization of dielectric and magnetic properties of ferroconcrete by using numerical electromagnetic field analysis software. The software is based on the Method of Moments (MoM. The shielding effectiveness (SE of the ferroconcrete DUT was already measured in a study by order of the government. According to these results, the ferroconcrete DUT is modelled and calculated. Therefore the DUT is subdivided into two parts. The first part represents the reinforcement mesh; the second part represents the lossy concrete with complex permittivity. Afterwards, the reflection and transmission properties of numerical analysed building materials are validated and compared with the measurement results in a frequency range of 30–1000 MHz.

  14. Dielectric Spectroscopy of Grape Juice at Microwave Frequencies

    Science.gov (United States)

    Vijay, Ravika; Jain, Ritu; Sharma, Krishna S.

    2015-04-01

    The complex permittivity of fresh juice of two cultivars of grapes, Sultania (green grapes) and Black Monukka (black grapes) was measured in terms of the dielectric constant and dielectric loss factor over the frequency range from 1 to 50 GHz and at temperatures ranging from 30 to 60°C, by using the PNA network analyzer model E8364C and open ended coaxial probe 85070E. The Cole-Cole plots and dielectric constant vs. (angular frequency) dielectric loss factor and dielectric constant vs. dielectric loss factor/(angular frequency) regression lines at different temperatures were used in Debye approximation to predict relaxation frequency of molecules for the two cultivars of grapes in the low frequency and high frequency limits, respectively. It was observed that the acidic character of green grapes is responsible for the large amplitude vibrational peaks in dielectric loss factor - frequency curves, in the high frequency region at higher temperatures. On the other hand, excess of sugar in black grapes suppresses the activity of water molecules, thereby suppressing the vibrational peaks at higher frequencies. Different relaxation frequencies found for the two cultivars of grapes suggest that they have different molecular structure.

  15. Investigation of dielectric properties of different cake formulations during microwave and infrared-microwave combination baking.

    Science.gov (United States)

    Sakiyan, Ozge; Sumnu, Gulum; Sahin, Serpil; Meda, Venkatesh

    2007-05-01

    Dielectric properties can be used to understand the behavior of food materials during microwave processing. Dielectric properties influence the level of interaction between food and high frequency electromagnetic energy. Dielectric properties are, therefore, important in the design of foods intended for microwave preparation. In this study, it was aimed to determine the variation of dielectric properties of different cake formulations during baking in microwave and infrared-microwave combination oven. In addition, the effects of formulation and temperature on dielectric properties of cake batter were examined. Dielectric constant and loss factor of cake samples were shown to be dependent on formulation, baking time, and temperature. The increase in baking time and temperature decreased dielectric constant and loss factor of all formulations. Fat content was shown to increase dielectric constant and loss factor of cakes.

  16. Frequency-dependent dielectric function of semiconductors with application to physisorption

    Science.gov (United States)

    Zheng, Fan; Tao, Jianmin; Rappe, Andrew M.

    2017-01-01

    The dielectric function is one of the most important quantities that describes the electrical and optical properties of solids. Accurate modeling of the frequency-dependent dielectric function has great significance in the study of the long-range van der Waals (vdW) interaction for solids and adsorption. In this work we calculate the frequency-dependent dielectric functions of semiconductors and insulators using the G W method with and without exciton effects, as well as efficient semilocal density functional theory (DFT), and compare these calculations with a model frequency-dependent dielectric function. We find that for semiconductors with moderate band gaps, the model dielectric functions, G W values, and DFT calculations all agree well with each other. However, for insulators with strong exciton effects, the model dielectric functions have a better agreement with accurate G W values than the DFT calculations, particularly in high-frequency region. To understand this, we repeat the DFT calculations with scissors correction, by shifting the DFT Kohn-Sham energy levels to match the experimental band gap. We find that scissors correction only moderately improves the DFT dielectric function in the low-frequency region. Based on the dielectric functions calculated with different methods, we make a comparative study by applying these dielectric functions to calculate the vdW coefficients (C3 and C5) for adsorption of rare-gas atoms on a variety of surfaces. We find that the vdW coefficients obtained with the nearly free electron gas-based model dielectric function agree quite well with those obtained from the G W dielectric function, in particular for adsorption on semiconductors, leading to an overall error of less than 7% for C3 and 5% for C5. This demonstrates the reliability of the model dielectric function for the study of physisorption.

  17. Hydrothermal synthesis and dielectric properties of lanthanum titanate ceramics

    Institute of Scientific and Technical Information of China (English)

    DENG Yuan; NAN Ce-wen

    2005-01-01

    Lanthanum titanate (La2/3TiO3) powders were synthesized by hydrothermal method based on the reaction of TiO2, La(NO3 )3 and KOH at 160 ℃ for 24 h followed by the treatment of acidification. The microstructure,morphology and dielectric properties were investigated by using X-ray diffraction, scanning electron microscope,transmission electron microscope and impedance method. The results show that the La2/3 TiO3 particles consist of nearly homogenous and lamellar grains. The particles can be sintered into porous ceramics above 1 150 ℃. The dielectric properties of La2/3 TiO3 show that both the dielectric constant and the dielectric loss tangent decrease with the increase of frequency.

  18. Frequency-dependent dielectric response model for polyimide-poly(vinilydenefluoride) multilayered dielectrics

    Science.gov (United States)

    Di Lillo, Luigi; Bergamini, Andrea; Albino Carnelli, Dario; Ermanni, Paolo

    2012-07-01

    A physical model for the frequency-dependent dielectric response of multilayered structures is reported. Two frequency regimes defined by the relative permittivities and volume resistivities of the layers have been analytically identified and experimentally investigated on a structure consisting of polyimide and poly(vinilydenefluoride) layers. The relative permittivity follows an effective medium model at high frequency while showing a dependence on the volume resistivity at low frequency. In this regime, relative permittivities exceeding those expected from effective medium model are recorded. These findings provide insights into inhomogeneous dielectrics behavior for the development of high energy density dielectric films.

  19. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co{sub 3}O{sub 4}-PVA/p-Si structures

    Energy Technology Data Exchange (ETDEWEB)

    Bilkan, Çiğdem, E-mail: cigdembilkan@gmail.com [Department of Physics, Faculty of Sciences, The University of Çankırı Karatekin, 18100 Çankırı (Turkey); Azizian-Kalandaragh, Yashar [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of); Altındal, Şemsettin [Department of Physics, Faculty of Sciences, The University of Gazi, 06500 Ankara (Turkey); Shokrani-Havigh, Roya [Department of Physics, Faculty of Science, The University of Mohaghegh Ardabili, Ardabil (Iran, Islamic Republic of)

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV–vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε′, ε″) and electric modulus (M′ and M″), loss tangent (tanδ), and ac electrical conductivity (σ{sub ac}) values of Al/Co{sub 3}O{sub 4}-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε′, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σ{sub dc} and σ{sub ac}, respectively. The M′ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M′ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and N{sub ss} effects with increasing frequency.

  20. Frequency and voltage dependence dielectric properties, ac electrical conductivity and electric modulus profiles in Al/Co3O4-PVA/p-Si structures

    Science.gov (United States)

    Bilkan, Çiğdem; Azizian-Kalandaragh, Yashar; Altındal, Şemsettin; Shokrani-Havigh, Roya

    2016-11-01

    In this research a simple microwave-assisted method have been used for preparation of cobalt oxide nanostructures. The as-prepared sample has been investigated by UV-vis spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM). On the other hand, frequency and voltage dependence of both the real and imaginary parts of dielectric constants (ε‧, ε″) and electric modulus (M‧ and M″), loss tangent (tanδ), and ac electrical conductivity (σac) values of Al/Co3O4-PVA/p-Si structures were obtained in the wide range of frequency and voltage using capacitance (C) and conductance (G/ω) data at room temperature. The values of ε‧, ε″ and tanδ were found to decrease with increasing frequency almost for each applied bias voltage, but the changes in these parameters become more effective in the depletion region at low frequencies due to the charges at surface states and their relaxation time and polarization effect. While the value of σ is almost constant at low frequency, increases almost as exponentially at high frequency which are corresponding to σdc and σac, respectively. The M‧ and M″ have low values at low frequencies region and then an increase with frequency due to short-range mobility of charge carriers. While the value of M‧ increase with increasing frequency, the value of M″ shows two peak and the peaks positions shifts to higher frequency with increasing applied voltage due to the decrease of the polarization and Nss effects with increasing frequency.

  1. Tailoring dielectric properties of ferroelectric-dielectric multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Kesim, M. T.; Zhang, J. [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Cole, M. W. [U.S. Army Research Laboratory, Weapons and Materials Research Directorate, Aberdeen Proving Ground, Maryland 21005 (United States); Misirlioglu, I. B. [Faculty of Engineering and Natural Sciences, Sabancı University, Orhanlı/Tuzla, 34956 Istanbul (Turkey); Alpay, S. P., E-mail: p.alpay@ims.uconn.edu [Department of Materials Science and Engineering and Institute of Materials Science, University of Connecticut, Storrs, Connecticut 06269 (United States); Department of Physics, University of Connecticut, Storrs, Connecticut 06269 (United States)

    2014-01-13

    We develop a nonlinear thermodynamic model for multilayer ferroelectric heterostructures that takes into account electrostatic and electromechanical interactions between layers. We concentrate on the effect of relative layer fractions and in-plane thermal stresses on dielectric properties of Ba{sub 0.6}Sr{sub 0.4}TiO{sub 3}-, BaTiO{sub 3}-, and PbZr{sub 0.2}Ti{sub 0.8}O{sub 3} (PZT)-SrTiO{sub 3} (STO) multilayers on Si and c-sapphire. We show that dielectric properties of such multilayers can be significantly enhanced by tailoring the growth/processing temperature and the STO layer fraction. Our computations show that large tunabilities (∼90% at 400 kV/cm) are possible in carefully designed barium strontium titanate-STO and PZT-STO even on Si for which there exist substantially large in-plane strains.

  2. Electrical, optical and dielectric properties of HCl doped polyaniline nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Chutia, P.; Kumar, A., E-mail: ask@tezu.ernet.in

    2014-03-01

    In this report we have investigated the optical, electrical and dielectric properties of HCl doped polyaniline nanorods synthesized by the interfacial polymerization technique. High resolution transmission electron microscope (HRTEM) micrographs confirm the formation of nanorods. X-ray diffraction pattern shows the semicrystalline nature of polyaniline nanorods with a diameter distribution in the range of 10–22 nm. The chemical and electronic structures of the polyaniline nanorods are investigated by micro-Raman and UV–vis spectroscopy. Dielectric relaxation spectroscopy has been applied to study the dielectric permittivity, modulus formalism and ac conductivity as a function of frequency and temperature. The ac conductivity follows a power law with frequency. The variation of frequency exponent with temperature suggests that the correlated barrier hopping is the dominant charge transport mechanism. The existence of both polaron and bipolaron in the transport mechanism has been confirmed from the binding energy calculations.

  3. Dielectric and electric properties of new chitosan-hydroxyapatite materials for biomedical application: Dielectric spectroscopy and corona treatment.

    Science.gov (United States)

    Petrov, Ivo; Kalinkevich, Oksana; Pogorielov, Maksym; Kalinkevich, Aleksei; Stanislavov, Aleksandr; Sklyar, Anatoly; Danilchenko, Sergei; Yovcheva, Temenuzhka

    2016-10-20

    Chitosan-hydroxyapatite composite materials were synthesized and the possibility to make their surface charged by corona discharge treatment has been evaluated. Dielectric and electric properties of the materials were studied by dielectric spectroscopy, including application of equivalent circuits method and computer simulations. Dielectric spectroscopy shows behavior of the materials quite different from that of both chitosan and HA alone. The obtained dielectric permittivity data are of particular interest in predicting the materials' behavior in electrostimulation after implantation. The ε values observed at physiological temperature in the frequency ranges applied are similar to ε data available for bone tissues.

  4. LOW-FREQUENCY DIELECTRIC RELAXATION IN SILVER STEARATE LAYERS

    Directory of Open Access Journals (Sweden)

    Smirnov, A.P.

    2016-05-01

    Full Text Available The low-frequency dielectric relaxation process in silver stearate layers was studied. The increasing of dielectric permittivity with frequency decreasing and temperature increasing in studied sample are associated with the dipole-relaxation polarization mechanisms. The dispersion of loss factor could be connected with the contribution of relaxation mechanism and conductivity. The shape of the Cole-Cole diagram shows that silver stearate is a non-Debye dielectric material characterized by a wide distribution of relaxators, according to the Cole-Cole relaxation model.

  5. Dielectric Property Measurements to Support Interpretation of Cassini Radar Data

    Science.gov (United States)

    Jamieson, Corey; Barmatz, M.

    2012-10-01

    Radar observations are useful for constraining surface and near-surface compositions and illuminating geologic processes on Solar System bodies. The interpretation of Cassini radiometric and radar data at 13.78 GHz (2.2 cm) of Titan and other Saturnian icy satellites is aided by laboratory measurements of the dielectric properties of relevant materials. However, existing dielectric measurements of candidate surface materials at microwave frequencies and low temperatures is sparse. We have set up a microwave cavity and cryogenic system to measure the complex dielectric properties of liquid hydrocarbons relevant to Titan, specifically methane, ethane and their mixtures to support the interpretation of spacecraft instrument and telescope radar observations. To perform these measurements, we excite and detect the TM020 mode in a custom-built cavity with small metal loop antennas powered by a Vector Network Analyzer. The hydrocarbon samples are condensed into a cylindrical quartz tube that is axially oriented in the cavity. Frequency sweeps through a resonance are performed with an empty cavity, an empty quartz tube inserted into the cavity, and with a sample-filled quartz tube in the cavity. These sweeps are fit by a Lorentzian line shape, from which we obtain the resonant frequency, f, and quality factor, Q, for each experimental arrangement. We then derive dielectric constants and loss tangents for our samples near 13.78 GHz using a new technique ideally suited for measuring liquid samples. We will present temperature-dependent, dielectric property measurements for liquid methane and ethane. The full interpretation of the radar and radiometry observations of Saturn’s icy satellites depends critically on understanding the dielectric properties of potential surface materials. By investigating relevant liquids and solids we will improve constrains on lake depths, volumes and compositions, which are important to understand Titan’s carbon/organic cycle and inevitably

  6. Microwave measurement and modeling of the dielectric properties of vegetation

    Science.gov (United States)

    Shrestha, Bijay Lal

    Some of the important applications of microwaves in the industrial, scientific and medical sectors include processing and treatment of various materials, and determining their physical properties. The dielectric properties of the materials of interest are paramount irrespective of the applications, hence, a wide range of materials covering food products, building materials, ores and fuels, and biological materials have been investigated for their dielectric properties. However, very few studies have been conducted towards the measurement of dielectric properties of green vegetations, including commercially important plant crops such as alfalfa. Because of its high nutritional value, there is a huge demand for this plant and its processed products in national and international markets, and an investigation into the possibility of applying microwaves to improve both the net yield and quality of the crop can be beneficial. Therefore, a dielectric measurement system based upon the probe reflection technique has been set up to measure dielectric properties of green plants over a frequency range from 300 MHz to 18 GHz, moisture contents from 12%, wet basis to 79%, wet basis, and temperatures from -15°C to 30°C. Dielectric properties of chopped alfalfa were measured with this system over frequency range of 300 MHz to 18 GHz, moisture content from 11.5%, wet basis, to 73%, wet basis, and density over the range from 139 kg m-3 to 716 kg m-3 at 23°C. The system accuracy was found to be +/-6% and +/-10% in measuring the dielectric constant and loss factor respectively. Empirical, semi empirical and theoretical models that require only moisture content and operating frequency were determined to represent the dielectric properties of both leaves and stems of alfalfa at 22°C. The empirical models fitted the measured dielectric data extremely well. The root mean square error (RMSE) and the coefficient of determination (r2) for dielectric constant and loss factor of leaves

  7. Microwave dielectric properties of lanthanum based complex perovskites

    Energy Technology Data Exchange (ETDEWEB)

    Nath, Masood A.; Samal, Saroj L. [Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016 (India); Obulesu, K. Rama; Raju, K.C. James [School of Physics, University of Hyderabad, Hyderabad 500 046 (India); Ganguli, Ashok K., E-mail: ashok@chemistry.iitd.ernet.in [Department of Chemistry, Indian Institute of Technology, Delhi, Hauz Khas, New Delhi 110 016 (India)

    2014-12-05

    Highlights: • Three new series of oxides with formula La{sub 2}BaTi{sub 2}M{sub 1−x}Cu{sub x}O{sub 9}, (M = Mg, Zn and Cd) have been synthesized by solid state method. • Such materials exhibit low loss and are used as resonators in wireless communication devices. • Detailed morphological studies and density measurements have confirmed the dielectric data. - Abstract: The present investigation discusses the synthesis and dielectric properties of three series of oxides of the formula La{sub 2}BaTi{sub 2}M{sub 1−x}Cu{sub x}O{sub 9} (where M = Mg, Zn and Cd). The reactions have been carried out via solid state method and all the compositions crystallize in the disordered cubic perovskite structure. Suitable substitution at both A and B sites lead to enhancement in the dielectric properties at high frequencies. The relative permittivity and loss tangent have been measured at X-band (8.2–12.4 GHz) and Ku-band (12.4–18 GHz) frequencies. The oxides show a dielectric constant of 20–30 while the dielectric loss is quite low in the order of 10{sup −3}–10{sup −4} (at 500 kHz) and 10{sup −2} at X and Ku-band. There is scope for further investigations in these systems to realize useful materials for microwave applications.

  8. Preparation and dielectric properties of porous silicon nitride ceramics

    Institute of Scientific and Technical Information of China (English)

    LI Jun-qi; LUO Fa; ZHU Dong-mei; ZHOU Wan-cheng

    2006-01-01

    Porous silicon nitride ceramics with difference volume fractions of porosity from 34.1% to 59.2% were produced by adding different amount of the pore-forming agent into initial silicon nitride powder. The microwave dielectric property of these ceramics at a frequency of 9.36 GHz was studied. The crystalline phases of the samples were determined by X-ray diffraction analysis. The influence of porosity on the dielectric properties was evaluated. The results show that α-Si3N4 crystalline phase exists in all the samples while the main crystalline phase of the samples is β-Si3N4,indicating that the a/b transformation happens during the preparation of samples and the transformation is incomplete. There is a dense matrix containing large pores and cavities with needle-shaped and flaky β-Si3N4 grains distributing. The dielectric constant of the ceramics reduces with the increase of porosity.

  9. Dielectrical properties of composites LDPE+CB

    Directory of Open Access Journals (Sweden)

    Škipina Blanka

    2010-01-01

    Full Text Available There is currently great interest in the technological properties of conductive polymer composites because their cost-performance balance. They have a wide range of industrial applications -in anti-static materials, self regulating heaters, current overload and overheating protection devices, and materials for electromagnetic radiation shielding. Measurements of the electrical properties of polymer composites are one of the most convenient and sensitive methods for studying polymer structure. A polymer composite differs substantially from a free polymer in a wide range of properties. The presence of filler affects both the electrical, as well as mechanical properties. One of the most important characteristics of conductive polymer composites is that their electrical conductivity increases nonlinearly with the increase of the concentration of filler particles. When the concentration of filler particles reaches a certain critical value, a drastic transition from an electrical insulator to a conductor is exhibited. This conductivity behavior resulting in a sudden insulator-conductor transition is ascribed to a percolation process, and the critical filler concentration at which the conductivity jump occurs is called ‘percolation threshold’. In the past few years, a lot of studies have been carried out to analyze the percolation phenomenon and mechanisms of the conductive behavior in conductive polymer composites. It has been established that the electrical conductivity of conductive polymer composites uncommonly depends on the temperature. Some of such composites show a sharp increase and/or decrease in electrical conductivity at specific temperatures. The conductive temperature coefficient (CTC of conductive polymer composites has been widely investigated. In these work we investigated how concentration of the CB affects the dielectrical properties of the composite LDPE+CB. The ac electrical conductivity, σac, for such composites was measured

  10. Synthesis modified structural and dielectric properties of semiconducting zinc ferrospinels

    Science.gov (United States)

    Kumari, N.; Kumar, V.; Singh, S. K.; Khasa, S.; Dahiya, M. S.

    2017-02-01

    The influence of preparation techniques on structural and dielectric properties of ZnCrxFe1-xO4 (x=0, 0.1 abbreviated as Z and ZC) ferrite nano-particles synthesized using chemical co-precipitation (CCP), sol-gel (SG) and solid state reaction (SS) techniques is discussed. XRD profiles are used to confirm the single phase spinel ferrite formation. TEM images indicate the change in size and shape of particles on changing either the composition or the synthesis methodology. The TEM micrograph of samples obtained through CCP shows uniform particle size formation compared to those obtained through SG and SS. Sample prepared through CCP possess porosity >70% making these materials suitable for sensing applications. The dielectric loss, dielectric constant and ac conductivity are analyzed as a function of frequency, temperature and composition using impedance spectroscopy. A universal dielectric behavior has been predicted through temperature and frequency variations of different parameters. Dielectric constant is found to possess highest value for sample synthesized through SG which marks the possibility of using the SG derived ferrospinels as microwave device components.

  11. Analytical Dielectric Spectrum Formula Based on Representative Frequencies

    Institute of Scientific and Technical Information of China (English)

    Bo Kong; Ke-xiang Fu; Min-hua Shan; Xiang-yuan Li

    2009-01-01

    According to experimental data available for the complex refractive index of particular di-electrics, a dielectric spectrum formula is proposed by the least square fitting technique combined with selected natural frequencies. From the dielectric spectrum formula, the spec-tra of optical and dielectric constants can be obtained in the whole frequency region. Three dielectrics, water, ethanol, and toluene, are taken as examples. In the region where the ex-perimental data are available, the spectra of the optical constants calculated by the formula are in good agreement with the real refractive spectrum obtained by Kramers-Kronig (K-K) transform and the experimental imaginary refractive spectrum. In the region where no ex-perimental data are available, the extrapolation of our formula can make predictions. The merits of the present treatment are that we are able to get the uniform spectrum formula, without splitting into different frequency sections, and the analytical form of the dielectric spectra will be useful in the theoretical description of solvation dynamics.

  12. Dielectric properties of binary solutions a data handbook

    CERN Document Server

    Akhadov, Y Y

    1980-01-01

    Dielectric Properties of Binary Solutions focuses on the investigation of the dielectric properties of solutions, as well as the molecular interactions and mechanisms of molecular processes that occur in liquids. The book first discusses the fundamental formulas describing the dielectric properties of liquids and dielectric data for binary systems of non-aqueous solutions. Topics include permittivity and dielectric dispersion parameters of non-aqueous solutions of organic and inorganic compounds. The text also tackles dielectric data for binary systems of aqueous solutions, including permittiv

  13. Influence of particle size on band gap and dielectric properties of TiO2 nanomaterials

    Science.gov (United States)

    Avinash B., S.; Chathurmukha V., S.; Naveen C., S.; Rajeeva M., P.; Jayanna H., S.; Lamani, Ashok R.

    2016-05-01

    In this work TiO2 nanomaterial of different particle size were synthesized by varying the pH of the solution by hydrolysis and peptization method. These samples were characterized by XRD, UV and SEM. The XRD reveals the formation of anatase phase form of TiO2 nanoparticles having the particle size in the range 15 nm to 35 nm. The calculated band gap values by Tauc plot for the prepared samples increases with decrease in particle size. These samples are pelletized to study the dielectric properties using Impedence Analyzer Interface in the frequency range from 1 Hz to 1 M Hz. From the dielectric studies it was observed that dielectric constant, tanδ and dielectric loss were maximum in lower frequency range, as the frequency increases these dielectric parameters decreases rapidly at low frequency region and almost constant values were recorded at higher frequencies. At lower frequencies, the dielectric parameters (dielectric constant, loss, and tanδ) increases with increase of pH up to pH 8 due to space charge polarization. The value of dielectric constant recorded at pH 10 is almost same as that of pH 8, for slight decrease in the values were recorded for dielectric loss and tan δ at pH 10 due to space charge polarization with the particle size.

  14. The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

    CERN Document Server

    Bouamrane, R

    2003-01-01

    An efficient algorithm, based on the Frank-Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor-capacitor (R-C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R-40% C, 50% R-50% C and 40% R-60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent pr...

  15. Electrical properties and dielectric spectroscopy of Ar+ implanted polycarbonate

    Science.gov (United States)

    Chawla, Mahak; Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu; Nair, K. G. M.

    2015-05-01

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar+ ions in the fluence ranging from 1×1014 to 1×1016 ions cm-2. The beam current used was ˜0.40 µA cm-2. The electrical conduction behaviour of virgin and Ar+ implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ɛ' vs. imaginary part of complex permittivity, ɛ″). The Cole-Cole plots have also been used to determine static dielectric constant (ɛs), optical dielectric constant (ɛ∞), spreading factor (α), average relaxation time (τ0) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar+ implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  16. Dielectric characterization of materials at microwave frequency range

    Directory of Open Access Journals (Sweden)

    J. de los Santos

    2003-01-01

    Full Text Available In this study a coaxial line was used to connect a microwave-frequency Network Analyzer and a base moving sample holder for dielectric characterization of ferroelectric materials in the microwave range. The main innovation of the technique is the introduction of a special sample holder that eliminates the air gap effect by pressing sample using a fine pressure system control. The device was preliminary tested with alumina (Al2O3 ceramics and validated up to 2 GHz. Dielectric measurements of lanthanum and manganese modified lead titanate (PLTM ceramics were carried out in order to evaluate the technique for a high permittivity material in the microwave range. Results showed that such method is very useful for materials with high dielectric permittivities, which is generally a limiting factor of other techniques in the frequency range from 50 MHz to 2 GHz.

  17. AC conductivity and dielectric properties of Co-doped TiO 2

    Science.gov (United States)

    Okutan, Mustafa; Basaran, Engin; Bakan, Halil I.; Yakuphanoglu, Fahrettin

    2005-07-01

    The alternating current (AC) conductivity and dielectric properties of the Co-doped TiO 2 were investigated. The temperature dependence of AC conductivity and the parameter s, is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energy ( E), and the density of states at Fermi level, N( EF) were determined. The dielectric constant decreases with frequency at low frequencies and increases at high frequencies.

  18. AC conductivity and dielectric properties of Co-doped TiO{sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Okutan, Mustafa [Department of Physics, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze (Turkey)]. E-mail: mustafa@gyte.edu.tr; Basaran, Engin [Department of Physics, Gebze Institute of Technology, P.O. Box 141, 41400 Gebze (Turkey); Bakan, Halil I. [TUBITAK-MAM, Materials and Chemical Research Institute, 41470 Gebze (Turkey); Yakuphanoglu, Fahrettin [Department of Physics, Faculty of Arts and Science, Firat University, 23169 Elazig (Turkey)

    2005-07-15

    The alternating current (AC) conductivity and dielectric properties of the Co-doped TiO{sub 2} were investigated. The temperature dependence of AC conductivity and the parameter s, is reasonably well interpreted by the correlated barrier hopping (CBH) model. The activation energy (E), and the density of states at Fermi level, N(E {sub F}) were determined. The dielectric constant decreases with frequency at low frequencies and increases at high frequencies.

  19. Tunable dielectric properties of ferrite-dielectric based metamaterial.

    Science.gov (United States)

    Bi, K; Huang, K; Zeng, L Y; Zhou, M H; Wang, Q M; Wang, Y G; Lei, M

    2015-01-01

    A ferrite-dielectric metamaterial composed of dielectric and ferrite cuboids has been investigated by experiments and simulations. By interacting with the electromagnetic wave, the Mie resonance can take place in the dielectric cuboids and the ferromagnetic precession will appear in the ferrite cuboids. The magnetic field distributions show the electric Mie resonance of the dielectric cuboids can be influenced by the ferromagnetic precession of ferrite cuboids when a certain magnetic field is applied. The effective permittivity of the metamaterial can be tuned by modifying the applied magnetic field. A good agreement between experimental and simulated results is demonstrated, which confirms that these metamaterials can be used for tunable microwave devices.

  20. Nanoscale Mapping of Dielectric Properties of Nanomaterials from Kilohertz to Megahertz Using Ultrasmall Cantilevers.

    Science.gov (United States)

    Cadena, Maria J; Sung, Seung Hyun; Boudouris, Bryan W; Reifenberger, Ronald; Raman, Arvind

    2016-04-26

    Electrostatic force microscopy (EFM) is often used for nanoscale dielectric spectroscopy, the measurement of local dielectric properties of materials as a function of frequency. However, the frequency range of atomic force microscopy (AFM)-based dielectric spectroscopy has been limited to a few kilohertz by the resonance frequency and noise of soft microcantilevers used for this purpose. Here, we boost the frequency range of local dielectric spectroscopy by 3 orders of magnitude from a few kilohertz to a few megahertz by developing a technique that exploits the high resonance frequency and low thermal noise of ultrasmall cantilevers (USCs). We map the frequency response of the real and imaginary components of the capacitance gradient (∂C(ω)/∂z) by using second-harmonic EFM and a theoretical model, which relates cantilever dynamics to the complex dielectric constant. We demonstrate the method by mapping the nanoscale dielectric spectrum of polymer-based materials for organic electronic devices. Beyond offering a powerful extension to AFM-based dielectric spectroscopy, the approach also allows the identification of electrostatic excitation frequencies which affords high dielectric contrast on nanomaterials.

  1. Optical Transmission Properties of Dielectric Aperture Arrays

    Science.gov (United States)

    Yang, Tao

    units (RIU) and a dynamic range as large as 0.17 RIU. Subsequently, optical transmission properties through a self-mixing interferometer array are studied and a novel high-resolution cost-effective optical spectrometer is proposed. The miniature interferometer-based spectrometer is made of polymethyl methacrylate (PMMA) with a CCD as the detector. The detected intensity of each CCD pixels contains the spectral information. Since each frequency component in the incoming beam corresponds to a unique phase difference of the two beam portions of each optical interferometer, the total intensity received by each CCD pixel, which is resulted from the addition of the interference signals from all the frequency components in the beam, should also be unique. Therefore, the spectrum calculation is a problem to solve an ill-posed linear system by using Tikhonov regularization method. Simulation results show that the resolution can reach picometer level. Apart from the choice of path difference between the interfering beams, the spectral resolution also depends on the signal-to-noise ratio and analogue-digital conversion resolution (dynamic range) of the CCD chip. In addition, the theory of uniform waveguide scattering is explored to expand the possibility of using such mini-interferometers for performing free-space spectral analysis of waveguide devices. At the same time, the method of least squares is used to correct the pixel non-uniformity of the CCD so as to improve the performance of the spectrometer. The sensor chip and spectrometer chip introduced here are based on the interference of light transmitted through dielectric aperture arrays. Their compact feature renders these devices ideal for miniaturization and integration as the systems in microfluidics architectures and lab-on-chip designs.

  2. Frequency-domain trade-offs for dielectric elastomer generators

    Science.gov (United States)

    Zanini, Plinio; Rossiter, Jonathan M.; Homer, Martin

    2017-04-01

    Dielectric Elastomer Generators (DEGs) are an emerging energy harvesting technology based on a the cyclic stretching of a rubber-like membrane. However, most design processes do not take into account different excitation frequencies; thus limits the applicability studies since in real-world situations forcing frequency is not often constant. Through the use of a practical design scenario we use modeling and simulation to determine the material frequency response and, hence, carefully investigate the excitation frequencies that maximize the performance (power output, efficiency) of DEGs and the factors that influence it.

  3. Handbook on dielectric and thermal properties of microwaveable materials

    CERN Document Server

    Komarov, Vyacheslav V

    2012-01-01

    The application of microwave energy for thermal processing of different materials and substances is a rapidly growing trend in modern science and engineering. In fact, optimal design work involving microwaves is impossible without solid knowledge of the properties of these materials. Here s a practical reference that collects essential data on the dielectric and thermal properties of microwaveable materials, saving you countless hours on projects in a wide range of areas, including microwave design and heating, applied electrodynamics, food science, and medical technology. This unique book provides hard-to-find information on complex dielectric permittivity of media at industrial, scientific, and medical frequencies (430 MHz, 915MHz, 2.45GHz, 5.8 GHz, and 24.125GHz). Written by a leading expert in the field, this authoritative book does an exceptional job at presenting critical data on various materials and explaining what their key characteristics are concerning microwaves.

  4. The Influence of Free Water Content on Dielectric Properties of Alkali Active Slag Cement Paste

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The dielectric performance of alkali activated slag (AAS) cement paste was investigated in the frequency range of 1 to 1000 MHz. The experimental results showed the unstable dielectric properties of harden paste were mostly influenced by the fraction of free water in paste or absorbed water from ambient, but not including hydration water and microstructure. The free water was completely eliminated by heat treatment at 105 ℃ about 4 hours, and then its dielectric loss was depressed; but with the exposure time in air increasing,the free water adsorption in ambient air made the dielectric property of harden cement paste to be bad. The temperature and relative humidity of environment was the key factors of free water adsorption; hence, if the influence of free water on dielectric constant was measured or eliminated, the cement-based materials may be applied in humidity sensitive materials or dielectric materials domains.

  5. Dielectric properties of ligand-modified gold nanoparticles/SU-8 photopolymer based nanocomposites

    KAUST Repository

    Toor, Anju

    2017-04-15

    This article reports the enhanced dielectric properties of a photodefinable nanocomposite material containing sub–10 nm coated metal nanoparticles (NPs). The surface morphology of the synthesized dodecanethiol-functionalized gold NPs was characterized using the transmission electron microscopy (TEM). We investigated the particle agglomeration and dispersion during the various stages of the nanocomposite synthesis using TEM. Physical properties such as dielectric permittivity and dielectric loss were measured experimentally. The dependence of dielectric permittivity and loss tangent on particle concentration and frequency was studied. Nanocomposite films showed an approximately three times enhancement in average dielectric constant over the polymer base value and an average dielectric loss of 0.09 at 1 kHz, at a filler loading of 10% w/w.

  6. Spacecraft dielectric material properties and spacecraft charging

    Science.gov (United States)

    Frederickson, A. R.; Wall, J. A.; Cotts, D. B.; Bouquet, F. L.

    1986-01-01

    The physics of spacecraft charging is reviewed, and criteria for selecting and testing semiinsulating polymers (SIPs) to avoid charging are discussed and illustrated. Chapters are devoted to the required properties of dielectric materials, the charging process, discharge-pulse phenomena, design for minimum pulse size, design to prevent pulses, conduction in polymers, evaluation of SIPs that might prevent spacecraft charging, and the general response of dielectrics to space radiation. SIPs characterized include polyimides, fluorocarbons, thermoplastic polyesters, poly(alkanes), vinyl polymers and acrylates, polymers containing phthalocyanine, polyacene quinones, coordination polymers containing metal ions, conjugated-backbone polymers, and 'metallic' conducting polymers. Tables summarizing the results of SIP radiation tests (such as those performed for the NASA Galileo Project) are included.

  7. Influence of color on dielectric properties of marinated poultry breast meat.

    Science.gov (United States)

    Samuel, D; Trabelsi, S

    2012-08-01

    The dielectric behavior of foods when exposed to radio-frequency and microwave electric fields is highly influenced by moisture content and the degree of water binding with constituents of the food materials. The ability to correlate specific food quality characteristics with the dielectric properties can lead to the development of rapid, nondestructive techniques for such quality measurements. Water-holding capacity is a critical attribute in meat quality. Up to 50% of raw poultry meat in the United States is marinated with mixtures of water, salts, and phosphates. The objective of this study was to determine if variations in breast meat color would affect the dielectric properties of marinated poultry meat over a broad frequency range from 500 MHz to 50 GHz. Poultry meat was obtained from a local commercial plant in Georgia (USA). Color and pH measurements were taken on the breast filets. Groups of breast filets were sorted into classes of pale and normal before adding marination pickup percentages of 0, 5, 10, and 15. Breast filets were vacuum-tumbled and weighed for pickup percentages. Dielectric properties of the filets were measured with a coaxial open-ended probe on samples equilibrated to 25°C. Samples from pale meat exhibited higher dielectric properties than samples from normal meat. No differences could be observed between samples from pale and normal meat after marination of the samples. Overall, dielectric properties increased as the marination pickup increased (α=0.05). Marination pickup strongly influenced the dielectric loss factor. Differences between samples marinated at different pickup levels were more pronounced at lower frequencies for the dielectric loss factor. As frequency increased, the differences between samples decreased. Differences in dielectric constant between samples were not as consistent as those seen with the dielectric loss factor.

  8. Structural, optical, morphological and dielectric properties of cerium oxide nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Prabaharan, Devadoss Mangalam Durai Manoharadoss [Department of Physics, NPR College of Engineering and Technology, Natham, Dindigul, Tamil Nadu (India); Sadaiyandi, Karuppasamy [Department of Physics, Alagappa Government Arts College, Karaikudi, Sivaganga, Tamil Nadu (India); Mahendran, Manickam [Department of Physics, Thiagarajar College of Engineering, Madurai, Tamil Nadu (India); Sagadevan, Suresh, E-mail: duraiphysics2011@gmail.com [Department of Physics, AMET University (India)

    2016-03-15

    Cerium oxide (CeO{sub 2}) nanoparticles were prepared by the precipitation method. The average crystallite size of cerium oxide nanoparticles was calculated from the X-ray diffraction (XRD) pattern and found to be 11 nm. The FT-IR spectrum clearly indicated the strong presence of cerium oxide nanoparticles. Raman spectrum confirmed the cubic nature of the cerium oxide nanoparticles. The Scanning Electron Microscopy (SEM) analysis showed that the nanoparticles agglomerated forming spherical-shaped particles. The Transmission Electron Microscopic (TEM) analysis confirmed the prepared cerium oxide nanoparticles with the particle size being found to be 16 nm. The optical absorption spectrum showed a blue shift by the cerium oxide nanoparticles due to the quantum confinement effect. The dielectric properties of cerium oxide nanoparticles were studied for different frequencies at different temperatures. The dielectric constant and the dielectric loss of the cerium oxide nanoparticles decreased with increase in frequency. The AC electrical conductivity study revealed that the conduction depended on both the frequency and the temperature. (author)

  9. Coupling between magnetism and dielectric properties in quantum paraelectric EuTiO3

    Science.gov (United States)

    Katsufuji, T.; Takagi, H.

    2001-08-01

    The dielectric constant of quantum paraelectric EuTiO3, which contains Eu2+ with S=7/2 spin and Ti4+, has been measured under a magnetic field. The dielectric constant shows a critical decrease at the antiferromagnetic ordering of the Eu spins at 5.5 K, as well as a substantial change under a magnetic field (by ~7% with 1.5 T), indicating a strong coupling between the Eu spins and dielectric properties. We show that the variation of the dielectric constant is dominated by the pair correlation of the nearest-neighbor Eu spins, likely via the variation of the soft-phonon-mode frequency.

  10. Tunable dielectric properties of ferrite-dielectric based metamaterial.

    Directory of Open Access Journals (Sweden)

    K Bi

    Full Text Available A ferrite-dielectric metamaterial composed of dielectric and ferrite cuboids has been investigated by experiments and simulations. By interacting with the electromagnetic wave, the Mie resonance can take place in the dielectric cuboids and the ferromagnetic precession will appear in the ferrite cuboids. The magnetic field distributions show the electric Mie resonance of the dielectric cuboids can be influenced by the ferromagnetic precession of ferrite cuboids when a certain magnetic field is applied. The effective permittivity of the metamaterial can be tuned by modifying the applied magnetic field. A good agreement between experimental and simulated results is demonstrated, which confirms that these metamaterials can be used for tunable microwave devices.

  11. High-k Dielectrics for Application in Broadband Radio Frequency-Microelectromechanical System Capacitive Shunt Switch

    Science.gov (United States)

    Zhang, Yi; Lu, Jian; Ichiki, Masaaki; Onodera, Kazumasa; Maeda, Ryutaro

    130 nm-thick lead zirconate titanate(PZT)/45 nm-thick HfO2 stack and single 45 nm-thick HfO2 dielectric film were utilized as insulator layer in π-type radio frequency (RF) capacitive shunt switches for achieving high isolation performance in broadband application. Thin PZT film in perovskite structure mainly with (1 1 1) orientation was successfully prepared at low temperature (500°C) using sol-gel method. The thin PZT film exhibited excellent ferroelectric properties and high dielectric constant (k ≈ 1185). Thin HfO2 film was prepared by sputtering method in a gas mixture of O2 and Ar. The thin HfO2 film had the dielectric constant of about 17 and the dielectric strength of about 24 MV/cm. The switch of PZT/HfO2 stack dielectric showed isolation performance better than -20 dB in the frequency range of 1 ∼ 35 GHz. The switch of HfO2 had isolation performance better than -40 dB in the frequency of 5 ∼ 35 GHz, suggesting its attractive prospective in practical broadband application.

  12. Dielectric properties of muscle and liver from 500 MHz-40 GHz.

    Science.gov (United States)

    Abdilla, Lourdes; Sammut, Charles; Mangion, Louis Zammit

    2013-06-01

    Dielectric properties are the most important parameters determining energy deposition when biological tissues are exposed to radio frequency and microwave fields. Energy absorption is determined by the specific absorption rate (SAR). SAR distributions can be computed accurately only if the complex relative permittivity of the target tissue is known to a sufficiently high accuracy, and currently there is a lack of data on the dielectric properties of biological tissues at high frequencies. In this study, tissue dielectric properties are measured using an open-ended coaxial probe technique from 500 MHz up to 40 GHz. We present dielectric data for ex vivo bovine and porcine muscle and liver tissues at 37 °C. One-pole Cole-Cole model is used to fit the measured data as a function of frequency and the dispersion parameters are presented. This data is supported by an accurate study on reference liquids such as methanol and ethanediol.

  13. Effects of acidic functional groups on dielectric properties of sodium alginates and carrageenans in water.

    Science.gov (United States)

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Okamura, Kei; Ueda, Tadaharu; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2015-01-22

    This study investigated the dielectric properties of sodium alginates and carrageenans in water at frequencies between 100 MHz and 20 GHz in regard to water-hydrocolloid interactions via acidic functional groups. Both sodium alginates and carrageenans showed conduction loss at lower frequencies and dielectric loss at higher frequencies. Reduction and desulfation of sodium alginates and carrageenans, which decreased the numbers of acidic functional groups, decreased their conduction loss. In addition, H(+)-form carrageenans showed the highest ionic conduction. Correlational analysis of dielectric properties and related physical parameters showed that the loss tangent (tanδ) of the hydrocolloid solution was determined by the conductivity of the aqueous solution. Especially at pH below 2, strong H(+) conduction was associated with high tanδ probably due to the Grotthuss mechanism. The molecular dynamics of free water and H(+), viscosity conditions were also suggested to be associated with dielectric property of water-hydrocolloid system.

  14. A Review: Origins of the Dielectric Properties of Proteins and Potential Development as Bio-Sensors.

    Science.gov (United States)

    Bibi, Fabien; Villain, Maud; Guillaume, Carole; Sorli, Brice; Gontard, Nathalie

    2016-08-04

    Polymers can be classified as synthetic polymers and natural polymers, and are often characterized by their most typical functions namely their high mechanical resistivity, electrical conductivity and dielectric properties. This bibliography report consists in: (i) Defining the origins of the dielectric properties of natural polymers by reviewing proteins. Despite their complex molecular chains, proteins present several points of interest, particularly, their charge content conferring their electrical and dielectric properties; (ii) Identifying factors influencing the dielectric properties of protein films. The effects of vapors and gases such as water vapor, oxygen, carbon dioxide, ammonia and ethanol on the dielectric properties are put forward; (iii) Finally, potential development of protein films as bio-sensors coated on electronic devices for detection of environmental changes particularly humidity or carbon dioxide content in relation with dielectric properties variations are discussed. As the study of the dielectric properties implies imposing an electric field to the material, it was necessary to evaluate the impact of frequency on the polymers and subsequently on their structure. Characterization techniques, on the one hand dielectric spectroscopy devoted for the determination of the glass transition temperature among others, and on the other hand other techniques such as infra-red spectroscopy for structure characterization as a function of moisture content for instance are also introduced.

  15. Microwave dielectric properties of wooden cross-arms

    Science.gov (United States)

    bin Khalid, Kaida; bin Shari, Mohd H.; Keong, Ng K.; Fuad, Syed A.

    1999-10-01

    When wooden poles and cross-arms are exposed to weather, its surface undergoes changes such warping, loss of some surface fibers and surface roughing. As a result of weathering, its unprotected surface tends to absorb more moisture as compare to the surface of sound wood. After the rain, the moisture will sustain in the weathered wood for some time before it is dried out. There is a possibility to relate the quality of the wooden cross-arms with the amount of its moisture content (MC) at a particular time. This work deals with the effect of weather on the dielectric properties of wooden cross-arms. The samples from sound wood, incipient decay and decay woods were chosen for dielectric study with frequency ranging from 0.2 GHz to 20 GHz. It is found that the decay wood can absorbed more than 70% MC (dry-basis) as compare to sound wood of only about 30% MC. The results of the dielectric measurement are compared with the values predicted by dielectric mixture equations. From the above study, there is a great possibility of using microwave reflection method to determine the moisture content and condition of wooden cross-arms.

  16. Millimeter Waveband Dielectric Properties of Nanocomposite Materials Based on Opal Matrices with Particles of Spinels

    Science.gov (United States)

    Rinkevich, A. B.; Perov, D. V.; Pakhomov, Ya A.; Samoylovich, M. I.; Kuznetsov, E. A.

    2016-09-01

    The dielectric properties of 3D nanocomposites based on opal matrices containing the particles of compounds with spinel structure have been studied. Microwave measurements have been carried out in the frequency range from 26 to 38 GHz. The frequency dependences of transmission and reflection coefficients are obtained. The values of the real and imaginary parts of complex dielectric permittivity have been retrieved. The X-ray phase analysis of the nanocomposites is performed and their structures are studied.

  17. Comparison effects and dielectric properties of different dose methylene-blue-doped hydrogels.

    Science.gov (United States)

    Yalçın, O; Coşkun, R; Okutan, M; Öztürk, M

    2013-08-01

    The dielectric properties of methylene blue (MB)-doped hydrogels were investigated by impedance spectroscopy. The real part (ε') and the imaginary part (ε") of the complex dielectric constant and the energy loss tangent/dissipation factor (tan δ) were measured in the frequency range of 10 Hz to 100 MHz at room temperature for pH 5.5 value. Frequency variations of the resistance, the reactance, and the impedance of the samples have also been investigated. The dielectric permittivity of the MB-doped hydrogels is sensitive to ionic conduction and electrode polarization in low frequency. Furthermore, the dielectric behavior in high-frequency parts was attributed to the Brownian motion of the hydrogen bonds. The ionic conduction for MB-doped samples was prevented for Cole-Cole plots, while the Cole-Cole plots for pure sample show equivalent electrical circuit. The alternative current (ac) conductivity increases with the increasing MB concentration and the frequency.

  18. Temperature and moisture dependence of the dielectric properties of silica sand.

    Science.gov (United States)

    Liu, Chenhui; Zhang, Libo; Peng, Jinhui; Srinivasakannan, Chandrasekar; Liu, Bingguo; Xia, Hongying; Zhou, Junwen; Xu, Lei

    2013-01-01

    The major objective of this work was to investigate the effects of temperature and moisture content on the dielectric properties of silica sand. The dielectric properties of moist silica sand at five temperatures between 20 to 100 degrees C, covering different moisture content levels at a frequency of 2.45 GHz, were measured with an open-ended coaxial probe dielectric measurement system. The wave penetration depth was calculated based on the measured dielectric data. The results show moisture content to be the major influencing factor for the variation of dielectric properties. Dielectric constant, loss factor and loss tangent all increase linearly with increasing moisture content. Three predictive empirical models were developed to relate the dielectric constant, loss factor, loss tangent of silica sand as a linear function of moisture content. An increase in temperature between 20 to 100 degrees C was found to increase the dielectric constant and loss factor. The penetration depth decreased with increase in moisture content and temperature. Variation in penetration depth was found to vary linearly with decrease in moisture content. An predictive empirical model was developed to calculate penetration depth for silica sand. This study offers useful information on dielectric properties of silica sand for developing microwave drying applications in mineral processing towards designing better microwave sensors for measuring silica sand moisture content.

  19. Materials Selection, Synthesis, and Dielectrical Properties of PVC Nanocomposites

    Directory of Open Access Journals (Sweden)

    Youssef Mobarak

    2013-01-01

    Full Text Available Materials selection process for electrical insulation application was carried out using Cambridge Engineering Selector (CES program. Melt mixing technique was applied to prepare polyvinyl-chloride- (PVC- nanofumed silica and nanomontmorillonite clay composites. Surface analysis and particles dispersibility were examined using scanning electron microscope. Dielectrical properties were assessed using Hipot tester. An experimental work for dielectric loss of the nanocomposite materials has been investigated in a frequency range of 10 Hz–50 kHz. The initial results using CES program showed that microparticles of silica and clay can improve electrical insulation properties and modulus of elasticity of PVC. Nano-montmorillonite clay composites were synthesized and characterized. Experimental analyses displayed that trapping properties of matrix are highly modified by the presence of nanofillers. The nanofumed silica and nanoclay particles were dispersed homogenously in PVC up to 10% wt/wt. Dielectric loss tangent constant of PVC-nanoclay composites was decreased successfully from 0.57 to 0.5 at 100 Hz using fillers loading from 1% to 10% wt/wt, respectively. Nano-fumed silica showed a significant influence on the electrical resistivity of PVC by enhancing it up to 1 × 1011 Ohm·m.

  20. A Free-Space Measurement Technique of Terahertz Dielectric Properties

    Science.gov (United States)

    Zhang, Xiansheng; Chang, Tianying; Cui, Hong-Liang; Sun, Zhonglin; Yang, Chuanfa; Yang, Xiuwei; Liu, Lingyu; Fan, Wei

    2017-03-01

    The free-space method for material dielectric characterization in the microwave band is extended to terahertz frequencies. By analyzing the advantages and disadvantages of the relative permittivity of the transmission/reflection method for non-magnetic materials, a fast calculation method using a transmission-only method is proposed. Based on the convergence analysis of the algorithm, a method to estimate the initial value is also proposed. Finally, through measurements of the permittivity of high-density polyethylene, polystyrene, polypropylene, and polymethyl methacrylate in the 325-500 GHz band, we verify the rationality of the algorithm and demonstrate its applicability. Through the combination of the two methods, the terahertz dielectric properties of a majority of flat non-conducting solid materials and non-polar liquid materials can be measured.

  1. Effect of Biomass Waste Filler on the Dielectric Properties of Polymer Composites

    Directory of Open Access Journals (Sweden)

    Yew Been Seok

    2016-07-01

    Full Text Available The effect of biomass waste fillers, namely coconut shell (CS and sugarcane bagasse (SCB on the dielectric properties of polymer composite was investigated. The aim of this study is to investigate the potential of CS and SCB to be used as conductive filler (natural source of carbon in the polymer composite. The purpose of the conductive filler is to increase the dielectric properties of the polymer composite. The carbon composition the CS and SCB was determine through carbon, hydrogen, nitrogen and sulphur (CHNS elemental analysis whereas the structural morphology of CS and SCB particles was examined by using scanning electron microscope. Room temperature open-ended coaxial line method was used to determine the dielectric constant and dielectric loss factor over broad band frequency range of 200 MHz-20 GHz. Based on this study, the results found that CS and SCB contain 48% and 44% of carbon, which is potentially useful to be used as conductive elements in the polymer composite. From SEM morphology, presence of irregular shape particles (size ≈ 200 μm and macroporous structure (size ≈ 2.5 μm were detected on CS and SCB. For dielectric properties measurement, it was measured that the average dielectric constant (ε' is 3.062 and 3.007 whereas the average dielectric loss factor (ε" is 0.282 and 0.273 respectively for CS/polymer and SCB/polymer composites. The presence of the biomass waste fillers have improved the dielectric properties of the polymer based composite (ε' = 2.920, ε" = 0.231. However, the increased in the dielectric properties is not highly significant, i.e. up to 4.86 % increase in ε' and 20% increase in ε". The biomass waste filler reinforced polymer composites show typical dielectric relaxation characteristic at frequency of 10 GHz - 20 GHz and could be used as conducting polymer composite for suppressing EMI at high frequency range.

  2. Frequency and temperature dependence of dielectric and electric properties of Ba2-xSm4+2x/3Ti8O24 with structural analysis

    OpenAIRE

    Narang Sukhleen Bindra; Kaur Dalveer; Pubby Kunal

    2015-01-01

    Dielectric ceramics samples of barium titanium oxide doped with samarium, having a complex structural formula of Ba2-xSm4+2x/3Ti8O24 (referred to as BST), were fabricated by a high temperature solid-state reaction technique with varying x (0.0, 0.2, 0.4, 0.6). X-ray diffraction technique was used to check the formation of particular phases. Scanning electron microscope technique was used to study the surface morphology of the samples. The samples were studied in a temperature range of 298 K t...

  3. Dielectric relaxation of relaxor ferroelectric P(VDF-TrFE-CFE) terpolymer over broad frequency range.

    Science.gov (United States)

    Wang, Yong; Lu, Sheng-Guo; Lanagan, Michael; Zhang, Qiming

    2009-03-01

    Dielectric properties of a relaxor ferroelectric polymer, poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) [P(VDF-TrFE-CFE)] terpolymer, were investigated over a broad range of frequency (from 0.1 kHz to 1 GHz) and a broad range of temperature (-20 degrees C to 76 degrees C). Time-temperature superposition was used to extrapolate the dielectric constant to high frequencies (approximately 1 GHz) from low frequency data (1 MHz). The consistency between the directly measured and the extrapolated data indicate that the time-temperature superposition can be applied at temperature ranging from the glass transition to the broad ferroelectric-paraelectric transition peak of relaxor, indicating that the glass transition is still the dominating relaxation process at room temperature for the ferroelectric relaxor. Compared with the dielectric properties of poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE] copolymer, the terpolymer shows a higher dielectric constant even at 1 GHz, which is considered to originate from the random defects modification converting the long-chain polar-molecular conformation to short-range molecular microstructures and enhancing the molecular motions in both polar and nonpolar nanodomains.

  4. Preparation, Characterization and Dielectric Properties of Epoxy and Polyethylene Nanocomposites

    Science.gov (United States)

    Zhang, Chao; Mason, Ralf; Stevens, Gary

    Two very different kinds of polymer nanocomposites have been prepared, characterized and investigated by dielectric spectroscopy to investigate the effects of polymer-nanofiller matrix difference on the dielectric response of nanodielectric composites. Linear low density polyethylene (LLDPE) is a non-polar thermoplastic which has a high viscosity even in the melt phase and bisphenol-A epoxy resin with an anhydride hardener is a polar low viscosity thermosetting resin. Nanometric sized aluminium oxide filler was chosen as the common inorganic phase for both nanodielectrics. Generally, nanoparticles aggregate easily and are difficult to separate due to strong surface interactions. In this study various mixing methods were employed from ultrasonic liquid processing to controlled shear flow mixing to investigate the dispersion of the nanofillers. The resultant epoxy and polyethylene nanocomposites were characterized with SEM, TEM, and DSC. The dielectric properties and frequency response of the nanocomposites were measured in the frequency domain from 10-2 Hz to 106 Hz at different temperatures. In polyethylene nanocomposites, significant interfacial polarization is clearly seen. However, in epoxy nanocomposites, no obvious interfacial polarization is found. The results are discussed in terms of the difference in the electrical characteristics of the interfacial region between the polymers and the nano-alumina.

  5. Dielectrical properties of PANI/TiO{sub 2} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Chaturmukha, V. S.; Naveen, C. S.; Rajeeva, M. P.; Avinash, B. S.; Jayanna, H. S.; Lamani, Ashok R., E-mail: ashok1571972@gmail.com [Department of PG Studies and Research in Physics, Kuvempu University, Shankaraghatta-577451, Shimoga, Karnataka (India)

    2016-05-23

    Conducting polyaniline/titanium dioxide (PANI/TiO{sub 2}) composites have been succesfully synthesized by insitu polymerization technique. The PANI/TiO{sub 2} nanocomposites of different compositions were prepared by varying weight percentage of TiO{sub 2} nanoparticles such as 10 wt%, 20 wt%, 30 wt%, 40 wt% and 50 wt% into the fixed amount of the aniline monomer. The prepared powder samples were characterized by X-ray diffractometer (XRD) and Scanning electron microscope (SEM). The intensity of diffraction peaks for PANI/TiO{sub 2} composites is lower than that for TiO{sub 2}. SEM pictures show that the nanocomposite were prepared in the form of long PANi chains decorated with TiO{sub 2} nanoparticles. The dielectric properties and AC conductivity were studied in the frequency range1K Hz–10M Hz. At higher frequencies, the composites exhibit almost zero dielectric loss and maximum value of σ{sub ac} is found for a concentration of 20 wt% TiO{sub 2} in polyaniline. The interface between polyaniline and TiO{sub 2} plays an important role in yielding a large dielectric constant in nanocomposites.

  6. Microtron Irradiation Induced Tuning of Dielectric Properties of LDPE-ZnO Nanocomposites

    Directory of Open Access Journals (Sweden)

    Deepu Thomas

    2015-01-01

    Full Text Available Low-density polyethylene (LDPE/ZnO composites were prepared using melt mixing process. ZnO powder with size of 44 nm was used as reinforcing particle. The electron beam irradiation effects on the dielectric behaviour of a polymer nanocomposite dielectric made of low density polyethylene filled with nanoparticles of ZnO were studied. The dielectric constant and dielectric loss values were determined by dielectric spectroscopy over a frequency range of 100 KHz–5 MHz on plane samples of the tested nanodielectrics. The influence of filler concentration, between 2 and 8 wt.%, and the irradiation effects on the dielectric properties are also discussed in the paper.

  7. Dielectric properties of Na1–K$_x$NbO3 in orthorhombic phase

    Indian Academy of Sciences (India)

    Vijendra Lingwal; B S Semwal; N S Panwar

    2003-10-01

    Pellets of ceramic, Na1–KNbO3 ( = 0, 0.2 and 0.5), were prepared by conventional solid-state reaction method. Prepared samples were characterized using XRD and SEM. The frequency and temperature variation of dielectric constant, loss tangent and dielectric conductivity of prepared samples were measured in the frequency range from 10 KHz–1 MHz, and in the temperature range from 50–250°C for = 0.2 and 0.5,and between 50 and 480°C for = 0 compositions. It was observed that the dielectric constant and loss tangent decrease, and conductivity increases with increasing frequency. Near the transition temperature the material shows anomalous behaviour for the observed properties, and the peaks of dielectric constant and loss tangent were observed shifting towards lower temperature with increasing frequency.

  8. Dielectric Behaviour of Zn/Al-NO3 LDHs Filled with Polyvinyl Chloride Composite at Low Microwave Frequencies

    Directory of Open Access Journals (Sweden)

    Ethar Y. Salih

    2014-01-01

    Full Text Available Recently, researchers have shown great interest in improving the thermal, mechanical, dielectric, and microwave properties of pure polymers through the use of polymer-based composites. The essential properties of polymer-based composites can be modified by varying the amount of Zn/Al-NO3 layered double hydroxide (LDH added to polyvinyl chloride (PVC. Therefore, by determining the optimal ratio of LDH in the PVC matrix, the dielectric properties of PVC-LDH composites can be improved. An LDH was prepared using the coprecipitation method, while PVC-LDH composites were prepared using tetrahydrofuran (THF as the solvent. The composites were characterised using X-ray diffraction (XRD, Fourier transform infrared spectroscopy (FTIR, and scanning electron microscopy (SEM, and room temperature dielectric measurements were investigated using an RF Impedance/Material Analyzer (Agilent 4291. The results confirmed that the prepared composites were pure. Additionally, the presence of LDH in the PVC matrix was verified. The dielectric measurements showed that an increase in the LDH concentration leads to an increase in the dielectric constant and the dielectric loss factor. When used as dielectric filler in the PVC matrix, the LDH improved the dielectric properties of the fabricated composites. The results indicate that these composites show great potential for use as microwave absorbers at low microwave frequencies.

  9. Dielectric properties of uncooked chicken breast muscles from ten to one thousand eight hundred megahertz.

    Science.gov (United States)

    Zhuang, H; Nelson, S O; Trabelsi, S; Savage, E M

    2007-11-01

    The dielectric properties, consisting of the dielectric constant (epsilon') and loss factor (epsilon''), were measured with an open-ended coaxial-line probe and impedance analyzer for uncooked broiler breast muscle pectoralis major and pectoralis minor, deboned at 2- and 24-h postmortem, over the frequency range from 10 to 1,800 MHz at temperatures ranging from 5 to 85 degrees C. The dielectric property profiles of chicken breast muscle are dependent upon the radio-wave and microwave frequencies and temperature. Increasing frequency from 10 to 1,800 MHz results in decreasing values of the dielectric constant and loss factor regardless of temperature in this range, chicken breast muscle type, or deboning time. However, the response to temperature varies with the frequency, muscle type, and deboning time. There are no differences in the dielectric constant and loss factor values at frequencies of 26 or 1,800 MHz between samples deboned at 2- and at 24-h postmortem. However, the muscle type significantly affects the average values of the dielectric constant and loss factor, with pectoralis minor having significantly higher average values. Both the deboning time and muscle type significantly affect the average values of the loss tangent (tan delta = dielectric loss factor/dielectric constant) at 26 and 1,800 MHz, with pectoralis minor having higher values than pectoralis major and 2-h samples having higher values than 24-h samples. Our quality measurements also show there are significant differences in chicken meat quality characteristics, including color, pH, drip loss, water holding capacity, and texture (Warner-Bratzler shear force value) between the different muscle types and between different deboning times in the same test. These results suggest that there is a probable potential for using dielectric property measurements to assess the quality of chicken meat.

  10. Meta-atom microfluidic sensor for measurement of dielectric properties of liquids

    Science.gov (United States)

    Awang, Robiatun A.; Tovar-Lopez, Francisco J.; Baum, Thomas; Sriram, Sharath; Rowe, Wayne S. T.

    2017-03-01

    High sensitivity microwave frequency microfluidic sensing is gaining popularity in chemical and biosensing applications for evaluating the dielectric properties of liquid samples. Here, we show that a tiny microfluidic channel positioned in the gaps of a dual-gap meta-atom split-ring resonator can exploit the electric field sensitivity to predict the dielectric properties of liquid samples. Employing an empirical relation between resonant characteristics of the fabricated sensor and the complex permittivity of water-ethanol or water-methanol mixtures produces good congruence to standardized values from the literature. This microfluidic sensor offers a potential lab-on-chip solution for liquid dielectric characterization without external electrical connections.

  11. New sample cell configuration for wide-frequency dielectric spectroscopy: DC to radio frequencies.

    Science.gov (United States)

    Nakanishi, Masahiro; Sasaki, Yasutaka; Nozaki, Ryusuke

    2010-12-01

    A new configuration for the sample cell to be used in broadband dielectric spectroscopy is presented. A coaxial structure with a parallel plate capacitor (outward parallel plate cell: OPPC) has made it possible to extend the frequency range significantly in comparison with the frequency range of the conventional configuration. In the proposed configuration, stray inductance is significantly decreased; consequently, the upper bound of the frequency range is improved by two orders of magnitude from the upper limit of conventional parallel plate capacitor (1 MHz). Furthermore, the value of capacitance is kept high by using a parallel plate configuration. Therefore, the precision of the capacitance measurement in the lower frequency range remains sufficiently high. Finally, OPPC can cover a wide frequency range (100 Hz-1 GHz) with an appropriate admittance measuring apparatus such as an impedance or network analyzer. The OPPC and the conventional dielectric cell are compared by examining the frequency dependence of the complex permittivity for several polar liquids and polymeric films.

  12. Effects of heavy metal on dielectric properties of E.coli revealed by dielectric spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Bai Wei; Zhao Kongshuang

    2006-01-01

    Dielectric spectroscopy of E.coli cell before and after exposure to heavy metals Cd2+,Cu2+, Zn2+ and Ca2+ was investigated. The results indicate that changes in dielectric spectra reflect effects of heavy metal on the structure and function of E.coli cells. Heavy metal can change membrane capacitance as well as permittivity and conductivity of the cytoplasm. Changes in volume fraction suggested that dielectric measurement could monitor the growth of E.coli cells. These results demonstrated that dielectric spectroscopy was a potential effective technique for studying electric properties of biological cells.

  13. Unraveling dielectric and electrical properties of ultralow-loss lead magnesium niobate titanate pyrochlore dielectric thin films for capacitive applications

    Science.gov (United States)

    Zhu, X. H.; Defaÿ, E.; Suhm, A.; Fribourg-Blanc, E.; Aïd, M.; Zhu, J. L.; Xiao, D. Q.; Zhu, J. G.

    2010-05-01

    PbO-MgO-Nb2O5-TiO2 (PMNT) pyrochlore thin films were prepared on Pt-coated silicon substrates by radio-frequency magnetron sputtering and postdeposition annealing method. Very interestingly, these pyrochlore-structured PMNT thin films exhibited ultralow dielectric losses, with a typical loss tangent as low as 0.001, and relatively high dielectric constants, typically ɛr˜170. It was found that the relative permittivity slightly but continuously increased upon cooling without any signature of a structural phase transition, displaying a quantum paraelectriclike behavior; meanwhile, the PMNT pyrochlore thin films did not show any noticeable dielectric dispersion in the real part of permittivity over a wide temperature range (77-400 K). Their dielectric responses could, however, be efficiently tuned by applying a dc electric field. A maximum applied bias field of 1 MV/cm resulted in a ˜20% tunability of the dielectric permittivity, giving rise to a fairly large coefficient of the dielectric nonlinearity, ˜2.5×109 J C-4 m-5. Moreover, the PMNT pyrochlore films exhibited superior electrical insulation properties with a relatively high breakdown field (Ebreakdown˜1.5 MV/cm) and a very low leakage current density of about 8.2×10-7 A/cm2 obtained at an electric field intensity as high as 500 kV/cm.

  14. Temperature-Dependent Dielectric Properties of Al/Epoxy Nanocomposites

    Science.gov (United States)

    Wang, Zijun; Zhou, Wenying; Sui, Xuezhen; Dong, Lina; Cai, Huiwu; Zuo, Jing; Chen, Qingguo

    2016-06-01

    Broadband dielectric spectroscopy was carried out to study the transition in electrical properties of Al/epoxy nanocomposites over the frequency range of 1-107 Hz and the temperature range of -20°C to 200°C. The dielectric permittivity, dissipation factor, and electrical conductivity of the nanocomposites increased with temperature and showed an abrupt increase around the glass transition temperature ( T g). The results clearly reveal an interesting transition of the electrical properties with increasing temperature: insulator below 70°C, conductor at about 70°C. The behavior of the transition in electrical properties of the nanocomposites was explored at different temperatures. The presence of relaxation peaks in the loss tangent and electric modulus spectra of the nanocomposites confirms that the chain segmental dynamics of the polymer is accompanied by the absorption of energy given to the system. It is suggested that the temperature-dependent transition of the electric properties in the nanocomposite is closely associated with the α-relaxation. The large increase in the dissipation factor and electric conductivity depends on the direct current conduction of thermally activated charge carriers resulting from the epoxy matrix above T g.

  15. Improvements of dielectric properties of Cu doped LaTiO3 þδ

    Institute of Scientific and Technical Information of China (English)

    Yan Chen; Jianxun Xu; Yimin Cui; Guangyi Shang; Jianqiang Qian; Jun-en Yao

    2016-01-01

    The ceramic composites of Cu-doped La1?xCuxTiO3þδ (x¼0.05, 0.15, 0.3, 0.5) were synthesized by con-ventional solid-state reaction. The complex dielectric properties of the composites were investigated as a function of temperature (77 KrTr320 K) and frequency (100 Hzrfr1 MHz) separately. In all com-posites, the dielectric constants increase monotonously and the dielectric loss undulates with tem-perature. And it is clearly observed that extraordinarily high low-frequency dielectric constant ( ? 104) appear at room temperature in La0.5Cu0.5TiO3þδ, which is ?100 times larger than that of La0.95Cu0.05TiO3 þδ. Interestingly, the dielectric constants increase remarkably with the doped Cu con-tents, meanwhile the dielectric loss for all samples is ideal lower than 1 at room temperature in the measured frequency range. By means of complex impedance analysis, the improvements of dielectric properties are attributed to both bulk contribution and grain boundary effect, in which the bulk polaronic relaxation and the Maxwell–Wagner relaxation due to grain boundary response are heightened re-markably with the high doped Cu contents.

  16. Photonic band gap enhancement in frequency-dependent dielectrics.

    Science.gov (United States)

    Toader, Ovidiu; John, Sajeev

    2004-10-01

    We illustrate a general technique for evaluating photonic band structures in periodic d -dimensional microstructures in which the dielectric constant epsilon (omega) exhibits rapid variations with frequency omega . This technique involves the evaluation of generalized electromagnetic dispersion surfaces omega ( k--> ,epsilon) in a (d+1) -dimensional space consisting of the physical d -dimensional space of wave vectors k--> and an additional dimension defined by the continuous, independent, variable epsilon . The physical band structure for the photonic crystal is obtained by evaluating the intersection of the generalized dispersion surfaces with the "cutting surface" defined by the function epsilon (omega) . We apply this method to evaluate the band structure of both two- and three-dimensional (3D) periodic microstructures. We consider metallic photonic crystals with free carriers described by a simple Drude conductivity and verify the occurrence of electromagnetic pass bands below the plasma frequency of the bulk metal. We also evaluate the shift of the photonic band structure caused by free carrier injection into semiconductor-based photonic crystals. We apply our method to two models in which epsilon (omega) describes a resonant radiation-matter interaction. In the first model, we consider the addition of independent, resonant oscillators to a photonic crystal with an otherwise frequency-independent dielectric constant. We demonstrate that for an inhomogeneously broadened distribution of resonators impregnated within an inverse opal structure, the full 3D photonic band gap (PBG) can be considerably enhanced. In the second model, we consider a coupled resonant oscillator mode in a photonic crystal. When this mode is an optical phonon, there can be a synergetic interplay between the polaritonic resonance and the geometrical scattering resonances of the structured dielectric, leading to PBG enhancement. A similar effect may arise when resonant atoms that are

  17. Dielectric properties of cowpea weevil, black eyed peas and mung beans with respect to the development of radio frequency heat treatments

    Science.gov (United States)

    In developing radio frequency (RF) and microwave (MW) disinfestation treatments for chickpeas and lentils, large amounts of product infested with cowpea weevil must be treated to validate treatment efficacy. To accomplish this, black-eyed peas and mung beans are being considered for use as surrogate...

  18. Evaluating Volume Fractions of the Elements for Composite Laminates by Using Dielectric Properties

    Institute of Scientific and Technical Information of China (English)

    周胜; 储才元; 严灏景

    2001-01-01

    A series and parallel model for investigating the capacity of composite laminates and the relationship between the dielectric properties of the composites and its constituents are presented. Volume fractions of the constituents are considered in this study. The expression of the complex dielectric constants for evaluating volume fractions under discrete frequencies is established and the general solutions for the resultant linear simultaneous equations for system are also exploited.The results show that the high accuracy of proposed method is obtained.

  19. Dielectric properties of cobalt ferrite nanoparticles in ultrathin nanocomposite films.

    Science.gov (United States)

    Alcantara, Gustavo B; Paterno, Leonardo G; Fonseca, Fernando J; Pereira-da-Silva, Marcelo A; Morais, Paulo C; Soler, Maria A G

    2013-12-07

    Multilayered nanocomposite films (thickness 50-90 nm) of cobalt ferrite nanoparticles (np-CoFe2O4, 18 nm) were deposited on top of interdigitated microelectrodes by the layer-by-layer technique in order to study their dielectric properties. For that purpose, two different types of nanocomposite films were prepared by assembling np-CoFe2O4 either with poly(3,4-ethylenedioxy thiophene):poly(styrene sulfonic acid) or with polyaniline and sulfonated lignin. Despite the different film architectures, the morphology of both was dominated by densely-packed layers of nanoparticles surrounded by polyelectrolytes. The dominant effect of np-CoFe2O4 was also observed after impedance spectroscopy measurements, which revealed that dielectric behavior of the nanocomposites was largely influenced by the charge transport across nanoparticle-polyelectrolyte interfaces. For example, nanocomposites containing np-CoFe2O4 exhibited a single low-frequency relaxation process, with time constants exceeding 15 ms. At 1 kHz, the dielectric constant and the dissipation factor (tan δ) of these nanocomposites were 15 and 0.15, respectively. These values are substantially inferior to those reported for pressed pellets made exclusively of similar nanoparticles. Impedance data were further fitted with equivalent circuit models from which individual contributions of particle's bulk and interfaces to the charge transport within the nanocomposites could be evaluated. The present study evidences that such nanocomposites display a dielectric behavior dissimilar from that exhibited by their individual counterparts much likely due to enlarged nanoparticle-polyelectrolyte interfaces.

  20. On Casimir Forces for Media with Arbitrary Dielectric Properties

    CERN Document Server

    Mochán, W L; Esquivel-Sirvent, R

    2002-01-01

    We derive an expression for the Casimir force between slabs with arbitrary dielectric properties characterized by their reflection coefficients. The formalism presented here is applicable to media with a local or a non-local dielectric response, an infinite or a finite width, inhomogeneous dissipative, etc. Our results reduce to the Lifshitz formula for the force between semi-infinite dielectric slabs by replacing the reflection coefficients by the Fresnel amplitudes.

  1. Dielectric properties of Rhodamine-B and metal doped hydrogels

    Energy Technology Data Exchange (ETDEWEB)

    Okutan, M. [Department of Physics, Yıldız Technical University, 34210 Istanbul (Turkey); Coşkun, R. [Department of Chemistry, Bozok University, 66100 Yozgat (Turkey); Öztürk, M. [Institute of Science, Niğde University, 51240 Niğde (Turkey); Yalçın, O., E-mail: o.yalcin@nigde.edu.tr [Department of Physics, Niğde University, 51240 Niğde (Turkey)

    2015-01-15

    The electric and dielectric properties of Rhodamine-B (RB) and metal ions (Ag{sup +}, Co{sup 2+}, Cr{sup 3+}, Mn{sup 2+} and Ni{sup 2+}) doped hydrogels have been analyzed in an extended frequency range by impedance spectroscopy. The RB doped hydrogels has been found to be sensitive to ionic conduction and electrode polarization according to the metal doped hydrogels. We have shown that the ionic conductive of RB doped hydrogels is originated from the free ions motion within the doped hydrogels at high frequency. We have also taken into account the Cl{sup −} and N{sup +} ions in the structure of RB provide additional ionic contribution to RB doped hydrogels.

  2. Electrical conductivity and dielectric properties of potassium sulfamate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A.S.; Iype, L.; Rajesh, R. [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam (India); Varughese, G. [Department of Physics, Catholicate College, Pathanamthitta, Kerala (India); Joseph, G. [Department of Physics, Sacred Heart College, Thevera, Cochin, Kerala (India); Louis, G. [Department of Physics, Cochin University of Science and Technology, Cochin (India)

    2011-10-15

    Single crystals of potassium sulfamate are grown by the method of slow evaporation at constant temperature. AC electrical conductivity of potassium sulfamate is measured in the temperature range 300-430 K and in the frequency region between 100 Hz and 3 MHz along the a, b and c-axes. Complex impedance spectroscopy is used to investigate the frequency response of the electrical properties of the potassium sulfamate single crystal. Temperature variation of AC conductivity and dielectric measurements show a slope change around 345 K for both heating and cooling run and this anomaly is attributed as phase transition, which is well supported by the DSC measurements. Value of loss tangent in the temperature region 330-400 K is found to be very low. Activation energies for the conduction process are calculated along the a, b and c-axes. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  3. Dielectric Properties of 3D Printed Polylactic Acid

    Directory of Open Access Journals (Sweden)

    Claudius Dichtl

    2017-01-01

    Full Text Available 3D printers constitute a fast-growing worldwide market. These printers are often employed in research and development fields related to engineering or architecture, especially for structural components or rapid prototyping. Recently, there is enormous progress in available materials for enhanced printing systems that allow additive manufacturing of complex functional products, like batteries or electronics. The polymer polylactic acid (PLA plays an important role in fused filament fabrication, a technique used for commercially available low-budget 3D printers. This printing technology is an economical tool for the development of functional components or cases for electronics, for example, for lab purposes. Here we investigate if the material properties of “as-printed” PLA, which was fabricated by a commercially available 3D printer, are suitable to be used in electrical measurement setups or even as a functional material itself in electronic devices. For this reason, we conduct differential scanning calorimetry measurements and a thorough temperature and frequency-dependent analysis of its dielectric properties. These results are compared to partially crystalline and completely amorphous PLA, indicating that the dielectric properties of “as-printed” PLA are similar to the latter. Finally, we demonstrate that the conductivity of PLA can be enhanced by mixing it with the ionic liquid “trihexyl tetradecyl phosphonium decanoate.” This provides a route to tailor PLA for complex functional products produced by an economical fused filament fabrication.

  4. Extraordinary refraction and self-collimation properties of multilayer metallic-dielectric stratified structures

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Liwei, E-mail: zlwhpu@hotmail.com [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Chen, Liang [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China); Zhang, Zhengren [School of Science, Chongqing Jiaotong University, Chongqing 400074 (China); Wang, Wusong [Guizhou Aerospace Institute of Measuring and Testing Technology, Guiyang 550009 (China); Zhao, Yuhuan; Song, Kechao; Kang, Chaoyang [School of Physics and Chemistry, Henan Polytechnic University, Jiaozuo 454000 (China)

    2015-01-15

    The extraordinary refraction with negative or zero refraction angle of the layered metamaterial consisting of alternating dielectric and plasmonic layers is theoretically studied. It is shown that the electromagnetic properties can be tuned by the filling factor, the permittivity of the dielectric layer and the plasma frequency of the metallic layer. At different frequency, the layered structures possess different refraction properties with positive, zero or negative refraction angle. By choosing appropriate parameters, positive-to-zero-to-negative-to positive refraction at the desired frequency can be realized. At the frequency with flat equal frequency contour, self-collimation and slow light properties are also found. Such properties can be used in the performance of negative refraction, subwavelength imaging and information propagation.

  5. Dielectric properties of tissues and biological materials: a critical review.

    Science.gov (United States)

    Foster, K R; Schwan, H P

    1989-01-01

    We critically review bulk electrical properties of tissues and other biological materials, from DC to 20 GHz, with emphasis on the underlying mechanisms responsible for the properties. We summarize the classical principles behind dielectric relaxation and critically review recent developments in this field. Special topics include a summary of the significant recent advances in theories of counterion polarization effects, dielectric properties of cancer vs. normal tissues, properties of low-water-content tissues, and macroscopic field-coupling considerations. Finally, the dielectric properties of tissues are summarized as empirical correlations with tissue water content in other compositional variables; in addition, a comprehensive table is presented of dielectric properties. The bulk electrical properties of tissues are needed for many bioengineering applications of electric fields or currents, and they provide insight into the basic mechanisms that govern the interaction of electric fields with tissue.

  6. Improvement in electric and dielectric properties of nanoferrite synthesized via reverse micelle technique

    Science.gov (United States)

    Thakur, Sangeeta; Katyal, S. C.; Singh, M.

    2007-12-01

    Nano nickel zinc ferrite (Ni0.58Zn0.42Fe2O4) with fascinating dielectric properties which reveal a direction for application was synthesized by reverse micelle technique. Dielectric constant and dielectric losses are controlled up to a measurement temperature of around 473K at higher frequency range of 9-19MHz. The dielectric loss of the sample investigated at room temperature is only 0.003 at 19MHz. The presently studied nanoferrite also exhibits a high value of dc resistivity, 108Ωcm. High resistivity and low dielectric constant and loss can be corelated to small grain size and better compositional stoichiometry obtained as a result of processing via reverse micelle technique at low sintering temperature (773K).

  7. Dielectric properties of poly (1,4-phenylene ether-ether-sulfone)

    CERN Document Server

    Spasevska, H

    2002-01-01

    Dielectric properties of Poly (1,4-phenylene ether-ether-sulfone) are obtained from dielectric spectroscopy of the polymer pellet. The values of relative dielectric constant epsilon', dielectric losses epsilon sup , dielectric dissipation factor tan delta and complex impedance are obtained at temperature of 75 sup o C. The temperature dependence of these parameters is investigated for three frequencies (8x10 sup 4 Hz; 8x10 sup 5 Hz; 8x10 sup 6 Hz) of applied electric field. The specific conductivity sigma, which depends on temperature, is related to the ohmic resistance R, at temperature in the interval from 66 to 83 sup o C. Fitting the experimental data, the value of the activation energy U is obtained. (Original)

  8. Low-frequency dielectric dispersion of bacterial cell suspensions.

    Science.gov (United States)

    Asami, Koji

    2014-07-01

    Dielectric spectra of Escherichia coli cells suspended in 0.1-10 mM NaCl were measured over a frequency range of 10 Hz to 10 MHz. Low-frequency dielectric dispersion, so-called the α-dispersion, was found below 10 kHz in addition to the β-dispersion, due to interfacial polarization, appearing above 100 kHz. When the cells were killed by heating at 60°C for 30 min, the β-dispersion disappeared completely, whereas the α-dispersion was little influenced. This suggests that the plasma (or inner) membranes of the dead cells are no longer the permeability barrier to small ions, and that the α-dispersion is not related to the membrane potential due to selective membrane permeability of ions. The intensity of the α-dispersion depended on both of the pH and ionic strength of the external medium, supporting the model that the α-dispersion results from the deformation of the ion clouds formed outside and inside the cell wall containing charged residues. Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Dielectric properties of piezoelectric 3–0 composites of lithium ferrite/barium titanate

    Indian Academy of Sciences (India)

    P Sarah; S V Suryanarayana

    2003-12-01

    Piezoelectric 3–0 composite ceramics are prepared from a mixture of barium titanate and lithium ferrite phase constituents. Dielectric properties of composites are affected by a number of parameters that include electrical properties, size, shape and amount of constituent phases. The frequency dependent measurements can provide additional insight into mechanisms controlling electrical response. Frequency dependence of dielectric constant plots of lithium ferrite/barium titanate composites will be given and the relevance of trends seen in them will be discussed. Connectivity in composites developed is studied.

  10. Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement.

    Science.gov (United States)

    Yao, Jiafeng; Kodera, Tatsuya; Obara, Hiromichi; Sugawara, Michiko; Takei, Masahiro

    2015-07-01

    The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry.

  11. Materials Selection, Synthesis, and Dielectrical Properties of PVC Nanocomposites

    OpenAIRE

    Youssef Mobarak; Bassyouni, M.; Almutawa, M.

    2013-01-01

    Materials selection process for electrical insulation application was carried out using Cambridge Engineering Selector (CES) program. Melt mixing technique was applied to prepare polyvinyl-chloride- (PVC-) nanofumed silica and nanomontmorillonite clay composites. Surface analysis and particles dispersibility were examined using scanning electron microscope. Dielectrical properties were assessed using Hipot tester. An experimental work for dielectric loss of the nanocomposite materials has bee...

  12. Structural and frequency dependencies of a.c. and dielectric characterizations of epitaxial InSb-based heterojunctions

    Indian Academy of Sciences (India)

    A ASHERY; A H ZAKI; M HUSSIEN MOURAD; A M AZAB; A A M FARAG

    2016-08-01

    In this work, heterojunction of InSb/InP was grown by liquid phase epitaxy (LPE). Surface morphology and crystalline structure of the heterojunction were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The frequency and temperature dependences of a.c. conductivity and dielectric properties of the heterojunctions were investigated in the ranges of 100 kHz–5 MHz and 298–628 K, respectively. The a.c. conductivity and its frequency exponents were interpreted in terms of correlated barrier hopping model (CBH), as the dominant conduction mechanism for charge carrier transport. The calculated activation energy, from the Arrhenius plot, was found to decrease with increasing frequency. Experimental results of both dielectric constant $\\epsilon_1$ and dielectric loss $\\epsilon_2$ showed a remarkable dependence of both frequency and temperature.

  13. Dielectric and thermophysical properties of different beef meat blends over a temperature range of -18 to +10°C.

    Science.gov (United States)

    Farag, K W; Lyng, J G; Morgan, D J; Cronin, D A

    2008-08-01

    Dielectric and thermophysical properties of three different beef meat blends (lean, fat and 50:50 mixture) were evaluated over a range of temperatures from -18 to +10°C. In the region of thawing (-3 to -1°C), dielectric constant (ε') and dielectric loss factor (ε') values for radio frequency (RF) and microwave (MW) were significantly higher (Pdielectric properties of the beef meat blends, with a general tendency towards higher values at the RF frequency. Finally, composition significantly influenced (Pdielectric and thermophysical properties at all temperatures used. These data are of potential value to food technologists in the context of rapid defrosting of meat products.

  14. Extraction and dielectric properties of curcuminoid films grown on Si substrate for high-k dielectric applications

    Energy Technology Data Exchange (ETDEWEB)

    Dakhel, A.A.; Jasim, Khalil E. [Department of Physics, College of Science, University of Bahrain, P.O. Box 32038 (Bahrain); Cassidy, S. [Department of Basic Medical Sciences, Royal College of Surgeons in Ireland, Medical University of Bahrain, P.O. Box 15503 (Bahrain); Henari, F.Z., E-mail: fzhenari@rcsi-mub.com [Department of Basic Medical Sciences, Royal College of Surgeons in Ireland, Medical University of Bahrain, P.O. Box 15503 (Bahrain)

    2013-09-20

    Highlights: • The unknown insulating properties of curcuminoid extract are systematically studied. • Optical study gives a bandgap of 3.15 eV and a refractive index of 1.92 at 505 nm. • Turmeric is a high-k environmental friendly material for use in microelectronics. • Curcuminoid extract can be used as insulator of MIS devices with ε{sup ′}{sub ∞}≈54.2. -- Abstract: Curcuminoids were extracted from turmeric powder and evaporated in vacuum to prepare thin films on p-Si and glass substrates for dielectric and optical investigations. The optical absorption spectrum of the prepared amorphous film was not identical to that of the molecular one, which was identified by a strong wide absorption band in between ∼220 and 540 nm. The onset energy of the optical absorption of the film was calculated by using Hamberg et al. method. The dielectric properties of this material were systematically studied for future eco friendly applications in metal–insulator–semiconductor MIS field of applications. The complex dielectric properties were studied in the frequency range of 1–1000 kHz and was analysed in-terms of dielectric impedance Z{sup *}(ω) and modulus M{sup *}(ω). Generally, the curcuminoid complex can be considered as a high-k material and can be used in the environmental friendly production of microelectronic devices.

  15. Aging of Dielectric Properties below Tg

    DEFF Research Database (Denmark)

    Olsen, Niels Boye; Dyre, Jeppe; Christensen, Tage Emil

    The dielectric loss at 1Hz in TPP is studied during a temperature step from one equilibrium state to another. In the applied cryostate the temperature can be equilibrated on a timescale of 1 second. The aging time dependence of the dielectric loss is studied below Tg applying temperature steps...

  16. Physical Properties of Triglycerides IV. Dielectric Constant

    NARCIS (Netherlands)

    Gouw, T.H.; Vlugter, J.C.

    1967-01-01

    Dielectric constants at 20° and at 40° C of a number of triglycerides in the liquid state have been measured. A molar additive function of the dielectric constant, based on a relation derived by J. van Elk, was used in combination with a previously derived equation for triglycerides to give an equat

  17. Dielectric Properties of Diesel and Gasoline by Terahertz Spectroscopy

    Science.gov (United States)

    Arik, Enis; Altan, Hakan; Esenturk, Okan

    2014-09-01

    In this study we have investigated the dielectric properties of diesel and gasoline in the Terahertz (THz) spectral region. We present frequency dependent absorption coefficients, refractive indices, and dielectric constants calculated from the transient measurements of the fuel oils between 0.1 and 1.1 THz. Observed weak absorption coefficient of fuel oils is explained by transient dipole moments induced by collisions between individual molecules. Fuel oils were modeled successfully with Debye model to investigate the relaxation dynamics after interaction with the electric field. Significant differences in relaxation times of molecules in diesel and gasoline are attributed to the differences in their intermolecular forces. Dispersion forces are much greater in diesel due to the longer hydrocarbon chains (C8-C40) compared to that (C4-C12) of the gasoline. This leads to a comparably faster relaxation right after THz electric field is applied. Clear differences in optical properties offer a simple yet effective way to discriminate fuel oils from each other by using THz spectroscopy without any danger of combustion or decomposition of the samples. Such an approach may also be used for the quality determination of either fuels. The study presents the great potential of THz spectroscopy to study very complex mixtures like fuel oils by the use of instantaneous THz wave/matter interactions and relaxation dynamics of the constituent molecules.

  18. Dielectric behavior of CaCu3Ti4O12: Poly Vinyl Chloride ceramic polymer composites at different temperature and frequencies

    Directory of Open Access Journals (Sweden)

    Ajay Pratap Singh

    2016-12-01

    Full Text Available In this study, the efforts have been made to obtain relatively high dielectric constant polymer-ceramic composite by incorporating the giant dielectric constant material, calcium copper titanate (CCTO in a PVC polymer matrix. We have prepared composites of CaCu3Ti4O12 (CCTO ceramic and Poly Vinyl Chloride (PVC polymer in various ratios (by volume in addition to pure CCTO. For this, CCTO was prepared by the conventional oxide route (solid-state reaction method. The structural, the microstructural and the dielectric properties of the composites were studied using X-ray diffraction, Scanning Electron Microscope, and impedance analyzer respectively. The study of dielectric constant and dielectric loss of the pure CCTO and the composites reveal that there is good range of dielectric constants and dielectric losses for the studied composites. The pure sample of CCTO exhibits giant dielectric constant at low frequency within the studied temperature range. As frequency increases, dielectric constant drastically decreases and approaching a constant value at 1 MHz. Above the intermediate temperature, the dielectric constant and dielectric loss for pure CCTO is more frequency dependent than its composites.

  19. Molecular dynamics simulations of the dielectric properties of fructose aqueous solutions

    Science.gov (United States)

    Sonoda, Milton T.; Elola, M. Dolores; Skaf, Munir S.

    2016-10-01

    The static dielectric permittivity and dielectric relaxation properties of fructose aqueous solutions of different concentrations ranging from 1.0 to 4.0 mol l-1 are investigated by means of molecular dynamics simulations. The contributions from intra- and interspecies molecular correlations were computed individually for both the static and frequency-dependent dielectric properties, and the results were compared with the available experimental data. Simulation results in the time- and frequency-domains were analyzed and indicate that the presence of fructose has little effect on the position of the fast, high-frequency (>500 cm-1) components of the dielectric response spectrum. The low-frequency (concentration. Our analysis indicates that fructose-fructose and fructose-water interactions strongly affect the rotational-diffusion regime of molecular motions in the solutions. Increasing fructose concentration not only enhances sugar-sugar and sugar-water low frequency contributions to the dielectric loss spectrum but also slows down the reorientational dynamics of water molecules. These results are consistent with previous computer simulations carried out for other disaccharide aqueous solutions.

  20. Improved gas sensing and dielectric properties of Fe doped hydroxyapatite thick films: Effect of molar concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Mene, Ravindra U. [PDEA' s, Annasaheb Waghire College of Science, Arts and Commerce, Otur 412409, M.S. (India); School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India); Mahabole, Megha P. [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India); Mohite, K.C. [Haribhai. V. Desai College, Pune 411002, M.S. (India); Khairnar, Rajendra S., E-mail: rskhairnarsps@gmail.com [School of Physical Sciences, Swami Ramanand Teerth Marathwada University, Nanded 431606, M.S. (India)

    2014-02-01

    Highlights: • We report improved gas sensing and dielectric characteristics of Fe ion exchanged HAp films. • Fe doped HAp film shows maximum gas response at relatively lower temperature. • Response and gas uptake capacity of sensors is improved for appropriate amount of Fe ions in HAp matrix. • Fe-HAp films exhibit remarkable improvement in dielectric properties compared to pure HAp. • Fe doped HAp films show significant improvement in gas sensing as well as in dielectric properties. - Abstract: In the present work Fe doped hydroxyapatite (Fe-HAp) thick films has been successfully utilized to improve the gas sensing as well as its dielectric properties. Initially, HAp nano powder is synthesized by chemical precipitation process and later on Fe ions are doped in HAp by ion exchange process. Structural and morphological modifications are observed by means of X-ray diffraction and scanning electron microscopy analysis. The sensing parameters such as operating temperature, response/recovery time and gas uptake capacity are experimentally determined. The Fe-HAp (0.05 M) film shows improved CO and CO{sub 2} gas sensing capacity at lower operating temperature compared to pure HAp. Moreover, variation of dielectric constant and dielectric loss for pure and Fe-HAp thick films are studied as a function of frequency in the range of 10 Hz–1 MHz. The study reveals that Fe doped HAp thick films improve the sensing and dielectric characteristics as compared to pure HAp.

  1. Dielectric properties of binary mixtures of methyl iso butyl ketone and amino silicone oil

    Science.gov (United States)

    Shah, K. N.; Rana, V. A.; Trivedi, C. M.; Vankar, H. P.

    2017-05-01

    Dielectric permittivity ɛ*(ω) = ɛ' - jɛ″ of the binary mixtures of the methyl iso butyl ketone and amino silicone oil in the frequency range 100 Hz to 2 MHz were measured using precision LCR meter at 305.15 K. Relative complex permittivity spectra in the frequency range 100 Hz to 2 MHz, of the mixture solutions of varying concentrations is reported. Determined values of the permittivity at optical frequency of all the samples are also reported. The dielectric parameters are used to gain information about the effect of concentration variation of components of the mixtures on the dielectric properties. It also provides the information about electrode polarization phenomena taking place under the low frequency A.C. electric field.

  2. SHI induced modification in structural, optical, dielectric and thermal properties of poly ethylene oxide films

    Science.gov (United States)

    Patel, Gnansagar B.; Bhavsar, Shilpa; Singh, N. L.; Singh, F.; Kulriya, P. K.

    2016-07-01

    Poly ethylene oxide (PEO) films were synthesized by solution cast method. These self-standing films were exposed with 60 MeV C+5 ion and 100 MeV Ni+7 ion at different fluences. SHI induced effect was investigated by employing various techniques. The crystalline size decreased upon irradiation as observed from XRD analysis. FTIR analysis reveals the decrement in the peak intensity upon irradiation. Tauc's method was used to determine the optical band gap (Eg), which shows decreasing trends with increase of fluence. The dielectric properties were investigated in the frequency range 10 Hz to 10 MHz for unirradiated and irradiated films. The dielectric constant remains same for the broad-spectrum of frequency and increases at lower frequency. The dielectric loss also moderately influence as a function of frequency due to irradiation. DSC analysis validated the results of XRD. Scanning electron microscopy (SEM) reveals that there is significant change in the surface morphology due to irradiation.

  3. Pyroelectric and dielectric properties of ferroelectric films with interposed dielectric buffer layers

    Science.gov (United States)

    Espinal, Y.; Kesim, M. T.; Misirlioglu, I. B.; Trolier-McKinstry, S.; Mantese, J. V.; Alpay, S. P.

    2014-12-01

    The dielectric and pyroelectric properties of c-domain ferroelectric films with linear dielectric buffer layers were investigated theoretically. Computations were carried out for multilayers consisting of PbZr0.2Ti0.8O3 with Al2O3, SiO2, Si3N4, HfO2, and TiO2 buffers on metalized Si. It is shown that the dielectric and pyroelectric properties of such multilayers can be increased by the presence of the buffer compared to ferroelectric monolayers. Calculations for PbZr0.2Ti0.8O3 films with 1% Al2O3 interposed between electrodes on Si show that the dielectric and pyroelectric coefficients are 310 and 0.070 μC cm-2 °C-1, respectively. Both values are higher than the intrinsic response of PbZr0.2Ti0.8O3 monolayer on Si.

  4. Dielectric Properties of Bi4Ti3O12 Ceramics by Impedance Spectroscopic Method

    Institute of Scientific and Technical Information of China (English)

    CHEN Yong; SU Huyin; XUE Simin; LI Zhaozhi; ZHANG Cancan; CHEN Qi; XU Lingfang; CAO Wanqiang; HUANG Zhaoxiang

    2016-01-01

    Various lead-free ceramics have been investigated in search for new high-temperature dielectrics. In particular, Bi4Ti3O12 is a type of ferroelectric ceramics, which is supposed to replace lead-containing ceramics for its outstanding dielectric properties in the near future. Ferroelectric ceramics of Bi4Ti3O12 made by conventional mixed oxide route have been studied by impedance spectroscopy in a wide range of temperature. X-ray diffraction patterns show that Bi4Ti3O12 ceramics are a single-phase of ferroelectric Bi-layered perovskite structure whether it is calcined at 800℃ or after sintering production. This study focused on the effect of the grain size on the electric properties of BIT ceramics. The BIT ceramics with different grain sizes were prepared at different sintering temperatures. Grain becomes coarser with the sintering temperature increasing by 50℃, relative permittivity and dielectric loss also change a lot. When sintered at 1 100℃, r values peak can reach 205.40 at a frequency of 100 kHz, the minimum dielectric losses of four different frequencies make no difference, all close to 0.027. The values ofEa range from 0.52 to 0.68 eV. The dielectric properties of the sample sintered at 1 100℃ are relatively better than those of the other samples by analyzing the relationship of the grain, the internal stresses, the homogeneity and the dielectric properties. SEM can better explain the results of the dielectric spectrum at different sintering temperatures. The results show that Bi4Ti3O12 ceramics are a kind of dielectrics. Thus, Bi4Ti3O12 can be used in high-temperature capacitors and microwave ceramics.

  5. Storage effects on dielectric properties of eggs from 10 to 1800 MHz.

    Science.gov (United States)

    Guo, W; Trabelsi, S; Nelson, S O; Jones, D R

    2007-06-01

    The dielectric constant and loss factor of egg albumen and egg yolk over the frequency range from 10 to 1800 MHz were measured at 24 degrees C at weekly intervals during 5-wk storage at 15 degrees C. Moisture and ash contents of albumen and yolk, as well as Haugh unit and yolk index, were also measured. The dielectric constant and loss factor of albumen were higher than those of yolk. Linear relationships were evident between the log of frequency, below about 1000 MHz, and the log of loss factor of albumen as well as that of yolk. The dielectric constants of albumen and yolk at 10 MHz were lower than those of fresh albumen and yolk when eggs were stored at 15 degrees C for 1 wk. However, after 2 wk in storage these dielectric constants rose and remained at higher levels for the rest of the 5-wk period. At frequencies of 100 MHz and higher, the dielectric constant was essentially constant during the entire storage period. Storage had much less influence on the loss factor of either albumen or yolk. In general, the moisture content and ash content of albumen and yolk decreased slightly as eggs aged. The moisture content of yolk increased somewhat with storage, and there was a corresponding decrease in albumen moisture content. The freshness qualities, Haugh unit and yolk index, also decreased as eggs aged. No obvious correlation between dielectric properties and moisture content, ash content, Haugh unit, or yolk index was observed.

  6. Microwave tunable dielectric properties of multilayer CNT membranes for smart applications

    Science.gov (United States)

    Liu, L.; Yang, Z. H.; Kong, L. B.; Yin, W. Y.; Wang, S.

    2012-09-01

    Multilayer multiwall carbon nanotube (MWCNT) silicone composite membranes with thickness greater than 10 μm were prepared with a spin-coating method. Dielectric permittivity and tunability of the circular membranes were measured from 0.1 to 7 GHz by using a single-port coaxial line method. The frequency and bias voltage dependent dielectric properties were interpreted based on percolation theory. The MWCNT membranes could be potentially used to develop smart components and structures working at radio wave or microwave frequencies.

  7. AC conductivity and dielectric properties of bulk tungsten trioxide (WO{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    El-Nahass, M.M. [Department of Physics, Faculty of Education, Ain Shams University, Roxy 11757, Cairo (Egypt); Ali, H.A.M., E-mail: hend2061@yahoo.com [Department of Physics, Faculty of Education, Ain Shams University, Roxy 11757, Cairo (Egypt); Saadeldin, M.; Zaghllol, M. [Physics Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2012-11-15

    AC conductivity and dielectric properties of tungsten trioxide (WO{sub 3}) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, {sigma}{sub ac}({omega}) was found to be a function of {omega}{sup s} where {omega} is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO{sub 3}. The dielectric constant ({epsilon} Prime ) and dielectric loss ({epsilon} Double-Prime ) were measured. The Cole-Cole diagram determined complex impedance for different temperatures.

  8. Electron current extraction from radio frequency excited micro-dielectric barrier discharges

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Jun-Chieh; Kushner, Mark J. [Electrical Engineering and Computer Science Department, University of Michigan, 1301 Beal Ave., Ann Arbor, Michigan 48109 (United States); Leoni, Napoleon; Birecki, Henryk; Gila, Omer [Hewlett Packard Research Labs, Palo Alto, California 94304 (United States)

    2013-01-21

    Micro dielectric barrier discharges (mDBDs) consist of micro-plasma devices (10-100 {mu}m diameter) in which the electrodes are fully or partially covered by dielectrics, and often operate at atmospheric pressure driven with radio frequency (rf) waveforms. In certain applications, it may be desirable to extract electron current out of the mDBD plasma, which necessitates a third electrode. As a result, the physical structure of the m-DBD and the electron emitting properties of its materials are important to its operation. In this paper, results from a two-dimensional computer simulation of current extraction from mDBDs sustained in atmospheric pressure N{sub 2} will be discussed. The mDBDs are sandwich structures with an opening of tens-of-microns excited with rf voltage waveforms of up to 25 MHz. Following avalanche by electron impact ionization in the mDBD cavity, the plasma can be expelled from the cavity towards the extraction electrode during the part of the rf cycle when the extraction electrode appears anodic. The electron current extraction can be enhanced by biasing this electrode. The charge collection can be controlled by choice of rf frequency, rf driving voltage, and permittivity of the dielectric barrier.

  9. Electromagnetic properties of metal-dielectric media and their applications

    Science.gov (United States)

    Animilli, Shravan Rakesh

    The main objective of this dissertation is to investigate nano-structured random composite materials, which exhibit anomalous phenomena, such as the extraordinary enhancements of linear and non-linear optical processes due to excitation of collective electronic states, surface plasmons (SP). The main goal is to develop a time and memory efficient novel numerical method to study the properties of these random media in three dimensions (3D) by utilization of multi core processing and packages such as MPI for parallel execution. The developed numerical studies are then utilized to provide a comprehensive characterization and optimization of a surface plasmon enhanced solar cell (SPESC) and to serve as a test bed for enhanced bio and chemical sensing. In this context, this thesis work develops an efficient and exact numerical algorithm here referred to as Block Elimination Method (BE) which provides the unique capability of modeling extremely large scale composite materials (with up to 1 million strongly interacting metal or dielectric particles). This capability is crucial in order to study the electromagnetic response of large scale inhomogeneous (fractal) films and bulk composites at critical concentrations (percolation). The developed numerical method is used to accurately estimate parameters that describe the composite materials, including the effective conductivity and correlation length scaling exponents, as well as density of states and localization length exponents at the band center. This works reveals, for a first time, a unique de-localization mechanism that plays an important role in the excitation of charge-density waves, i.e. surface plasmons (SP), in metal-dielectric composites. It also shows that in 3D metal-dielectric percolation systems the local fields distribution function for frequencies close to the single particle plasmon resonance is log-normal which is a signature of a metal-dielectric phase transition manifested in the optical response of the

  10. Scandium doped Strontium Titanate Ceramics: Structure, Microstructure, and Dielectric Properties

    Directory of Open Access Journals (Sweden)

    Tkach, Alexander

    2008-08-01

    Full Text Available Sc-doped strontium titanate (ST ceramics were synthesised by solid state reaction, according to the composition Sr1-1.5xScxTiO3 with x = 0-0.01. Structural properties and microstructure development was examined by XRD and SEM. The dielectric properties were evaluated as a function of the temperature and frequency in the radio frequency range. Lattice parameter, density and grain size, were found to decrease slightly with increasing Sc content. The dielectric permittivity and losses decrease also. Sc-doping has only a weak effect on the quantum paraelectric behaviour of ST and no dielectric anomaly was observed, what is probably related to the limited solubility of Sc on the Sr site of the perovskite lattice of ST.

    Se sintetizaron materiales cerámicos de titanato de estroncio dopado con escandio mediante reacción en estado sólido De acuerdo a la composición Sr1-1.5xScxTiO3 con x= 0-0.1. Las propiedades estructurales y el desarrollo microestructural se estudiaron mediante XRD y SEM. La propiedades dieléctricas se estudiaron como función de la temperatura y de la frecuencia en el rango de la frecuencias de radio. Se observó que los parámetros de red, la densidad y el tamaño del grano disminuyen ligeramente con el contenido en Sc. La permitividad dieléctrica y las perdidas también disminuyen. El dopado con Sc tiene un efecto muy ligero sobre el comportamiento paraeléctrico cuántico del titanato de estroncio y no se observó anomalías dioeléctricas , lo que está probablemente relacionado con la baja solubilidad del Sc en posiciones del Sr en la estructura tipo perovskita del titanato de estroncio.

  11. Dielectric properties of tetragonal tungsten bronze films deposited by RF magnetron sputtering

    OpenAIRE

    Bodeux, Romain; Michau, Dominique; Josse, Michaël; Maglione, Mario

    2014-01-01

    International audience; Tetragonal tungsten bronze (TTB) films have been synthesised on Pt(111)/TiO2/SiO2/Si substrates from Ba2LnFeNb4O15 ceramics (Ln = La, Nd, Eu) by RF magnetron sputtering. X-ray diffraction measurements evidenced the multi-oriented nature of films with some degrees of preferential orientation along (111). The dependence of the dielectric properties on temperature and frequency has been investigated. The dielectric properties of the films are similar to those of the bulk,...

  12. Influence of Doping Concentration on Dielectric, Optical, and Morphological Properties of PMMA Thin Films

    Directory of Open Access Journals (Sweden)

    Lyly Nyl Ismail

    2012-01-01

    Full Text Available PMMA thin films were deposited by sol gel spin coating method on ITO substrates. Toluene was used as the solvent to dissolve the PMMA powder. The PMMA concentration was varied from 30 ~ 120 mg. The dielectric properties were measured at frequency of 0 ~ 100 kHz. The dielectric permittivity was in the range of 7.3 to 7.5 which decreased as the PMMA concentration increased. The dielectric loss is in the range of 0.01 ~ –0.01. All samples show dielectric characteristics which have dielectric loss is less than 0.05. The optical properties for thin films were measured at room temperature across 200 ~ 1000 nm wavelength region. All samples are highly transparent. The energy band gaps are in the range of 3.6 eV to 3.9 eV when the PMMA concentration increased. The morphologies of the samples show that all samples are uniform and the surface roughness increased as the concentration increased. From this study, it is known that, the dielectric, optical, and morphology properties were influenced by the amount of PMMA concentration in the solution.

  13. Dependence of dielectric properties on BT particle size in EP/BT composites

    Institute of Scientific and Technical Information of China (English)

    YANG Xiaojun; YANG Zhimin; MAO Changhui; DU Jun

    2006-01-01

    The polymer-ceramic composites of epoxy resin (EP) and barium titanate (BT) were prepared.BT powders of different BT particle sizes from 100 nm to 1 μm were used in the preparation.The dielectric properties, such as dielectric constant, dielectric loss and electrical breakdown strength, of the EP/BT composites were studied.The morphology of the composites was characterized by the means of scanning electron microscopy (SEM).The results show that the dielectric constant of the composites is much higher than the epoxy matrix at frequency range from 1 kHz to 10 MHz, and it is also obviously dependent on the size of BT particles.The electrical breakdown strength of the composites decreases with the increase of the BT content.The dependence of electrical breakdown strength on BT particle sizes was also discussed.

  14. Tuning the dielectric properties of thiourea analog crystals for efficient nonlinear optical applications

    Energy Technology Data Exchange (ETDEWEB)

    Sabari Girisun, T.C. [Department of Physics, Bishop Heber College, Tiruchirappalli 620 017, Tamil Nadu (India); School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India); Dhanuskodi, S., E-mail: dhanus2k3@yahoo.com [School of Physics, Bharathidasan University, Tiruchirappalli 620 024, Tamil Nadu (India)

    2010-01-15

    Materials with low dielectric constant have attracted a great deal of interest in the field of nonlinear applications and microelectronic industry. Metal complexes of thiourea with group II transition metals (Zn, Cd) as central atom and period III elements (S, Cl) were synthesized by chemical reaction method and single crystals were grown from aqueous solution by slow evaporation method. By parallel plate capacitor technique, the dielectric response, dissipation factor, ac conductivity and impedance of virgin and metal complexes have been studied in the frequency (100 Hz to 5 MHz) and temperature (303-423 K) ranges. Metal complexes of thiourea with cadmium substitute have a low dielectric constant less than 10. Also the presence of chlorine in the metal complex induces noncentro symmetric structure. Hence the role of group II transition metals and period III elements in tuning the dielectric properties for efficient nonlinear applications has been studied.

  15. Electrical and Dielectric Properties of Exfoliated Graphite/Polyimide Composite Films with Low Percolation Threshold

    Science.gov (United States)

    Yu, Li; Zhang, Yi-He; Shang, Jiwu; Ke, Shan-Ming; Tong, Wang-shu; Shen, Bo; Huang, Hai-Tao

    2012-09-01

    Exfoliated graphite/polyimide composite films were synthesized by in situ polymerization. The electrical and dielectric properties of composite films with different volume fraction of exfoliated graphite were investigated over the frequency range from 103 Hz to 3 × 106 Hz. The dielectric behavior of the composite films was investigated by percolation theory and a microcapacitor model. A low percolation threshold f c ≈ 3.1 vol.% was obtained due to the high aspect ratio of the exfoliated graphite. Both the dielectric constant and alternating-current (AC) conductivity showed an abrupt increase in the vicinity of the percolation threshold. The ultralarge enhancement of the dielectric constant near and beyond the percolation threshold was due to Maxwell-Wagner-Sillars (MWS) interfacial polarization between the exfoliated graphite and polyimide and interface polarization between the composite film and electrode.

  16. Synthesis and dielectric properties of Zn doped GdFeO3 ceramics

    Science.gov (United States)

    Sai Vandana, C.; Guravamma, J.; Hemalatha Rudramadevi, B.

    2016-09-01

    GdFeO3 and GdZn0.3Fe0.7O3 ceramics were prepared by standard Solid State Reaction method at 1200°C. The structural changes and crystallite sizes of the undoped and Zn doped ceramics were studied using the XRD data. Microstructural features and elemental composition of GdFeO3 and GdZn0.3Fe0.7O3 ceramics were determined from SEM and EDS analysis. Room temperature dielectric measurements such as dielectric constant (ɛ´), tangent loss (tan5) and AC conductivity (oac) were carried out in the frequency range (100Hz to 1MHz). Improved dielectric properties of GdZn0.3Fe0.7O3 over GdFeO3 ceramics with low values of dielectric loss render them as potential materials in the areas of microwave communication systems, information storage, spintronics, sensors, etc.

  17. Tunable optical properties of silver-dielectric-silver nanoshell

    Science.gov (United States)

    Shirzaditabar, Farzad; Saliminasab, Maryam

    2014-05-01

    Tunable optical properties of silver-dielectric-silver nanoshell including surface plasmon resonance (SPR) and resonance light scattering (RLS) based on quasi-static theory are investigated. When the silver core radius increases, the longer resonance wavelength red shifts and light scattering cross-section decreases whereas the shorter resonance wavelength blue shifts and the light scattering cross-section increases. The effect of middle dielectric thickness on the light scattering cross-section of nanoshell is different from those of the silver core radius changes. As middle dielectric radius increases, the longer resonance wavelength first blue shifts and then red shifts and the light scattering cross-section increases whereas the shorter resonance wavelength always red shifts and the light scattering cross-section decreases. The sensitivity of RLS to the refractive index of embedding medium is also reported. As the silver core radius increases, the sensitivity of silver-dielectric-silver nanoshell decreases whereas increasing the middle dielectric thickness leads to increase the sensitivity of silver-dielectric-silver nanoshell. Tunable optical properties of silver-dielectric-silver nanoshell verify the biosensing potential of this nanostructure.

  18. Vibrational and dielectric properties of magnesium aluminate spinel: A first-principles study

    Energy Technology Data Exchange (ETDEWEB)

    Zeng, Qingfeng, E-mail: qfzeng@nwpu.edu.cn [National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Zhang, Litong [National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China); Zhang, Xian; Chen, Qichao [School of Technical Physics, Xidian University, Xi' an, Shaanxi 710071 (China); Feng, Zhiqiang [School of Mechanics and Engineering, Southwest Jiaotong University, Chengdu, Sichuan 611756 (China); Laboratoire de Mecanique et d' Energetique, Universite d' Evry, Evry 91020 (France); Cai, Yongqing [Department of Physics, National University of Singapore, Singapore 117542 (Singapore); Cheng, Laifei; Weng, Zuohai [National Key Laboratory of Thermostructure Composite Materials, Northwestern Polytechnical University, Xi' an, Shaanxi 710072 (China)

    2011-09-19

    The vibrational and dielectric properties of MgAl{sub 2}O{sub 4} are investigated within the framework of density functional perturbation theory. Results of phonon frequencies at the Brillouin zone center, static dielectric constant, and electronic dielectric constant are reported. In comparison with experimental results, we find that the generalized gradient approximation potential results in more accurate phonon frequencies than local density approximation potential does. Dielectric, refractive index, extinction coefficient and infrared reflectance spectra of MgAl{sub 2}O{sub 4} are given, and the figures suggest that MgAl{sub 2}O{sub 4} presents good transmission properties in the spectrum range above 1000 cm{sup -1} and below 300 cm{sup -1}. -- Highlights: → MgAl{sub 2}O{sub 4} has an electronic dielectric constant smaller than the lattice component. → GGA potential results in more accurate phonon frequencies compared to LDA potential. → Weak reflection peaks at 321 cm{sup -1} and 596 cm{sup -1} result in narrow LO-TO bands. → Infrared spectrum suggests good transmission above 1000 cm{sup -1} and below 300 cm{sup -1}.

  19. Dielectric properties of biological tissues in which cells are connected by communicating junctions

    Science.gov (United States)

    Asami, Koji

    2007-06-01

    The frequency dependence of the complex permittivity of biological tissues has been simulated using a simple model that is a cubic array of spherical cells in a parallel plate capacitor. The cells are connected by two types of communicating junctions: one is a membrane-lined channel for plasmodesmata in plant tissues, and the other is a conducting patch of adjoining plasma membranes for gap junctions in animal tissues. Both junctions provided similar effects on the dielectric properties of the tissue model. The model without junction showed a dielectric relaxation (called β-dispersion) that was expected from an interfacial polarization theory for a concentrated suspension of spherical cells. The dielectric relaxation was the same as that of the model in which neighbouring cells were connected by junctions perpendicular to the applied electric field. When neighbouring cells were connected by junctions parallel to the applied electric field or in all directions, a dielectric relaxation appeared at a lower frequency side in addition to the β-dispersion, corresponding to the so called α-dispersion. When junctions were randomly introduced at varied probabilities Pj, the low-frequency (LF) relaxation curve became broader, especially at Pj of 0.2-0.5, and its intensity was proportional to Pj up to 0.7. The intensity and the characteristic frequency of the LF relaxation both decreased with decreasing junction conductance. The simulations indicate that communicating junctions are important for understanding the LF dielectric relaxation in tissues.

  20. Band-gap tunable dielectric elastomer filter for low frequency noise

    Science.gov (United States)

    Jia, Kun; Wang, Mian; Lu, Tongqing; Zhang, Jinhua; Wang, Tiejun

    2016-05-01

    In the last decades, diverse materials and technologies for sound insulation have been widely applied in engineering. However, suppressing the noise radiation at low frequency still remains a challenge. In this work, a novel membrane-type smart filter, consisting of a pre-stretched dielectric elastomer membrane with two compliant electrodes coated on the both sides, is presented to control the low frequency noise. Since the stiffness of membrane dominates its acoustic properties, sound transmission band-gap of the membrane filter can be tuned by adjusting the voltage applied to the membrane. The impedance tube experiments have been carried out to measure the sound transmission loss (STL) of the filters with different electrodes, membrane thickness and pre-stretch conditions. The experimental results show that the center frequency of sound transmission band-gap mainly depends on the stress in the dielectric elastomer, and a large band-gap shift (more than 60 Hz) can be achieved by tuning the voltage applied to the 85 mm diameter VHB4910 specimen with pre-stretch {λ }0=3. Based on the experimental results and the assumption that applied electric field is independent of the membrane behavior, 3D finite element analysis has also been conducted to calculate the membrane stress variation. The sound filter proposed herein may provide a promising facility to control low frequency noise source with tonal characteristics.

  1. Low frequency dielectric spectroscopy of bitumen binders as an indicator of adhesion potential to quartz aggregates using Portland cement

    OpenAIRE

    Lyne, Åsa Laurell; Taylor, Nathaniel; Jaeverberg, Nadja; Edin, Hans; Birgisson, Björn

    2015-01-01

    The purpose of this investigation was to interpret the bitumen-aggregate adhesion based on the dielectric spectroscopic response of individual material components utilizing their dielectric constants, refractive indices and average tangent of the dielectric loss angle (average loss tangent). Dielectric spectroscopy of bitumen binders at room temperature was performed in the frequency range of 0.01–1000 Hz. Dielectric spectroscopy is an experimental method for characterizing the dielectric per...

  2. Mechanical and dielectric properties of carbon nanotubes/poly (vinyl alcohol) nanocomposites

    Science.gov (United States)

    Amrin, Sayed; Deshpande, V. D.

    2016-05-01

    In this work, two series of nanocomposites of poly(vinyl alcohol) (PVA) incorporated with multiwalled carbon nanotubes (MWNT) and carboxyl functionalized multiwalled carbon nanotubes (MWNT-COOH) were fabricated using solution-cast method and their tensile and dielectric properties were studied. Tensile tests were carried out on composite films of MWNT/PVA and MWNT-COOH/PVA for different loading levels. Results show that overall mechanical properties of the MWNT-COOH/PVA composite was greatly improved as compared to the MWNT/PVA film. The dielectric properties of nanocomposites were investigated in a frequency range from 0.1Hz to 10MHz at room temperature respectively. Compared to MWNT/PVA composites, higher dielectric constant and ac conductivity was achieved in MWNT-COOH/PVA nanocomposite, which can be well explained by the interfacial polarization effect.

  3. Dielectric Properties and Defect Structure of Bi-doped SrTiO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The dielectric properties of ceramics with composition of (Sr1-xBix)TiO3+x/2(where x=0.05~0.70 ) were measured at frequency of 1 MHz. The experimental results indicate that the dielectric properties of (Sr1-xBix)TiO3+x/2 system are greatly varied with an increase of the stoichiometric amounts of Bi2O3. The relative permittivity of the solid solutions is high, and the dissipation factor is low. The positron annihilation technique(PAT) was adopted to study the defect structure. An explanation of the dielectric properties of Bi-doped SrTiO3 ceramics has been suggested in terms of electron-compensation and vacancy or defect-compensation mechanisms and space-charge polarization mechanism.

  4. Functional group dependent dielectric properties of sulfated hydrocolloids extracted from green macroalgal biomass.

    Science.gov (United States)

    Tsubaki, Shuntaro; Hiraoka, Masanori; Hadano, Shingo; Nishimura, Hiroshi; Kashimura, Keiichiro; Mitani, Tomohiko

    2014-07-17

    Dielectric properties of aqueous solutions of sulfated hydrocolloids (ulvan and rhamnan sulfate) extracted from green macroalgal biomass were studied in a frequency range of 100 MHz-10 GHz. Counterion exchange of native hydrocolloids (mixture of Na(+), Mg(2+) and Ca(2+)) to H(+)-form showed significant increase in loss factor due to ionic conduction. On the other hand, desulfations decreased their loss factors. The results suggested that ionic conduction of H(+) has significant contribution to loss factors. Additionally, H(+)-form hydrocolloids showed significant improvement in hydration, which might also affect the dielectric property of the solution by reducing the amount of free water. The viscosity, however, did not show apparent relevance with the dielectric property.

  5. Investigation of Plasma Polymerized Maleic Anhydride Film in a Middle Frequency Dielectric Barrier Discharge

    Institute of Scientific and Technical Information of China (English)

    TANG Wenjie; CHEN Qiang; ZHANG Yuefei; GE Yuanjing

    2008-01-01

    Plasma polymerized maleic anhydride (MA) was carried out by using maleic anhydride supersaturated ethanol solution as a precursor in a dielectric barrier discharge (DBD). The film properties were characterized by water contact angle (WCA), Fourier transfer infrared (FTIR), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM) analysis, and a thickness profilometer. The influence of the processing parameters on the film properties such as the power frequency, and polymerization zone was investigated. The results show that anhydride group incorporated into the growing films is favorable at the frequency of 80 kHz and working pressure of 50 Pa. The poly (maleic anhydride) film is uniform and compact at an average deposition rate of 8 nm/min.

  6. Dielectric Resonator Antennas: Basic Concepts, Design Guidelines, and Recent Developments at Millimeter-Wave Frequencies

    Directory of Open Access Journals (Sweden)

    S. Keyrouz

    2016-01-01

    Full Text Available An up-to-date literature overview on relevant approaches for controlling circuital characteristics and radiation properties of dielectric resonator antennas (DRAs is presented. The main advantages of DRAs are discussed in detail, while reviewing the most effective techniques for antenna feeding as well as for size reduction. Furthermore, advanced design solutions for enhancing the realized gain of individual DRAs are investigated. In this way, guidance is provided to radio frequency (RF front-end designers in the selection of different antenna topologies useful to achieve the required antenna performance in terms of frequency response, gain, and polarization. Particular attention is put in the analysis of the progress which is being made in the application of DRA technology at millimeter-wave frequencies.

  7. Synthesis, Characterization and Properties of Ca5A2TiO12 (A=Nb, Ta) Ceramic Dielectric Materials for Applications in Microwave Telecommunication Systems

    Science.gov (United States)

    Bijumon, Pazhoor Varghese; Mohanan, Pezholil; Sebastian, Mailadil Thomas

    2002-06-01

    Microwave ceramic dielectric materials Ca5Nb2TiO12 and Ca5Ta2TiO12 have been prepared by a conventional solid-state ceramic process. The structure was studied by X-ray diffraction and the dielectric properties were characterized at microwave frequencies. The ceramics posses a relatively high dielectric constant, very low dielectric loss (Qu× f> 30000 GHz) and small temperature variation of resonant frequency. These materials are potential candidates for dielectric resonator applications in microwave integrated circuits.

  8. Structural aspects in the dielectric properties of pentyl alcohols

    Science.gov (United States)

    Kaatze, Udo; Behrends, Ralph; von Roden, Kerstin

    2010-09-01

    At temperatures between 0 and 60 °C densities, shear viscosities and dielectric spectra have been measured for isomers 1-pentanol, 2-pentanol, 3-pentanol, isopentylalcohol, and tert-pentanol, as well as for mixtures of these alcohols. The density and shear viscosity data are discussed in terms of deviations from ideal mixing behavior. The dielectric spectra are evaluated to yield the extrapolated static permittivity and the relaxation time of the principal (low-frequency) relaxation term. The former parameter is analyzed in view of dipole orientation correlations, the latter one is discussed in terms of the activation enthalpy controlling the relaxation process. A noticeable result is the effect of isomer structure on both the dipole orientation correlation and the dielectric relaxation. Especially the dielectric parameters of tert-pentanol deviate significantly from the relevant parameters of the other pentanols. Such deviations are considered in the light of models of hydrogen network structure and fluctuations.

  9. Magnetic and dielectric properties and Raman spectroscopy of GdCrO3 nanoparticles

    Science.gov (United States)

    Jaiswal, Adhish; Das, Raja; Vivekanand, K.; Maity, Tuhin; Abraham, Priya Mary; Adyanthaya, Suguna; Poddar, Pankaj

    2010-01-01

    The rare earth orthochromites are extremely interesting due to the richness of their optical, dielectric, and magnetic properties as well as due to their multiferroic properties which make them suitable materials to study in the nanoregime. However, the wet-chemical synthesis of these materials in nanosize is nontrivial. Here, we report for the first time, the detailed Raman spectra as well as magnetic and dielectric properties of chemically synthesized GdCrO3 nanoparticles of size ranging from 40 to 60 nm. The magnetic properties are dictated by competing Cr3+-Cr3+, Gd3+-Cr3+, and Gd3+-Gd3+ superexchange interactions in different temperature regions, resulting into an antiferromagnetic ordering at 167 K due to the Cr3+-Cr3+ followed by weak ferromagnetic ordering due to the onset of Cr3+-Gd3+ interactions. At lower temperature, it shows weak antiferromagnetic ordering due to Gd3+-Gd3+ interaction. Below 95 K, GdCrO3 nanoparticles showed the presence of negative magnetization due to Gd3+ and Cr3+ interactions resulting into weak ferromagnetic coupling. The Raman spectroscopy shows the characteristic Raman shifts indicating that below 450 cm-1, Gd3+ ions play a dominant role in determining the phonon frequencies of GdCrO3, and above 450 cm-1, the Cr+3 ions dominate. We also present for the first time the low temperature dielectric constant and loss tangent data for GdCrO3 in a broad temperature and frequency range. The dielectric constant shows a decrease in comparison to the bulk values due to the size dependent effects. It also shows a peak centered at around 320 K above which it shows a sharp decrease. The dielectric loss value in GdCrO3 nanoparticles is quite small and shows an interesting frequency dependent anomaly at lower temperature which might be due to the coupling between magnetic and dielectric order parameters.

  10. A Millimeter Wave Colgate Structure Dielectric Antenna with the built-in Diode Frequency Multiplier

    OpenAIRE

    2003-01-01

    The dielectric antennas in millimeter wave region are very useful for the broadband mobile applications with small power dissipation. The colgate structure which is the one of the dielectric leakage antenna, should be longer in the size. We designed. the 'squeezed colgate type antenna and show that the antenna have low antenna directivities. This paper show the experiments of the antenna performance. Moreover the diode frequency multiplier is adapted to the dielectric antenna.

  11. Measurement of the Dielectric Properties of Volcanic Scoria and Basalt at 9370 MHz

    Institute of Scientific and Technical Information of China (English)

    ZHENG Yongchun; WANG Shijie; OUYANG Ziyuan; LI Xiongyao

    2005-01-01

    Dielectric data for volcanic scoria and basalt on the earth at microwave frequency are extremely sparse, and also crucial for volcanic terrains imaging, and development. In consideration of their similarity to lunar regolith (soils and rocks) in chemical and mineral composition, the dielectric data is significative for passive and active microwave remote sensing on the Moon. This study provides the data about the dielectric properties of three kinds of scoria and two kinds of basalt in China. The method put forward in this paper is also applicable for measuring the dielectric properties of dry rocks and other granular ground materials with low complex dielectric constants. Firstly, the authors measured the ε' and tanδvalues of strip specimens prepared from the mixture of scoria or basalt powder and polythene with the resonant cavity perturbation method at 9370 MHz. Secondly, from the ε' and tanδ values of the mixture, the ε's and ranδs values of solid scoria and basalt were calculated using Lichtenecker's mixture formulae. Finally, the effective complex dielectric constants, ε'e and tanδe, of scoria at different bulk densities were calculated. The results have shown that the ε's and tancδs values of all solid basaltic materials measured (both solid basaltic scoria or basalt) are approximately 7 and 0.05, respectively. With increasing bulk density of scoria, the ε'e and tanδe values of scoria increase significantly.

  12. NIR emission studies and dielectric properties of Er(3+)-doped multicomponent tellurite glasses.

    Science.gov (United States)

    Sajna, M S; Thomas, Sunil; Jayakrishnan, C; Joseph, Cyriac; Biju, P R; Unnikrishnan, N V

    2016-05-15

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~63 nm), stimulated emission cross-section (9.67 × 10(-21) cm(2)) and lifetime (2.56 ms) of (4)I13/2 level for 0.5 mol% of Er(3+) makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er(3+) ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er(3+) -doped glass was confirmed as the optimum composition.

  13. NIR emission studies and dielectric properties of Er3+-doped multicomponent tellurite glasses

    Science.gov (United States)

    Sajna, M. S.; Thomas, Sunil; Jayakrishnan, C.; Joseph, Cyriac; Biju, P. R.; Unnikrishnan, N. V.

    2016-05-01

    Multicomponent tellurite glasses containing altered concentrations of Er2O3 (ranging from 0 to 1 mol%) were prepared by the standard melt quenching technique. Investigations through energy dispersive X-ray spectroscopy (EDS), Raman scattering spectroscopy, Fourier transform infrared (FTIR) spectroscopy, near-infrared (NIR) emission studies and dielectric measurement techniques were done to probe their compositional, structural, spectroscopic and dielectric characteristics. The broad emission together with the high values of the effective linewidth (~ 63 nm), stimulated emission cross-section (9.67 × 10- 21 cm2) and lifetime (2.56 ms) of 4I13/2 level for 0.5 mol% of Er3+ makes these glasses attractive for broadband amplifiers. From the measured capacitance and dissipation factor, the relative permittivity, dielectric loss and the conductivity were computed; which furnish the dielectric nature of the multicomponent tellurite glasses that depend on the applied frequency. Assuming the ideal Debye behavior as substantiated by Cole-Cole plot, an examination of the real and imaginary parts of impedance was performed. The power-law and Cole-Cole parameters were resolved for all the glass samples. From the assessment of the emission analysis and dielectric properties of the glass samples, it was obvious that the Er3+ ion concentration had played a vital role in tuning the optical and dielectric properties and the 0.5 mol% of Er3+ -doped glass was confirmed as the optimum composition.

  14. Structural Characteristics & Dielectric Properties of Tantalum Oxide Doped Barium Titanate Based Materials

    Directory of Open Access Journals (Sweden)

    Rubayyat Mahbub

    2012-11-01

    Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mol% Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90% was achieved for 0.5 and 1.0 mol% Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0·5 mol% Ta2O5. Although fine grain size down to 200-300nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000-14000 was found in the temperature range of  55 to 80°C, for 1.0 mol% Ta2O5 doped samples with corresponding shift of Curie point to ~82°C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

  15. STRUCTURAL CHARACTERISTICS & DIELECTRIC PROPERTIES OF TANTALUM OXIDE DOPED BARIUM TITANATE BASED MATERIALS

    Directory of Open Access Journals (Sweden)

    Md. Fakhrul Islam

    2013-01-01

    Full Text Available In this research, the causal relationship between the dielectric properties and the structural characteristics of 0.5 & 1.0 mole % Ta2O5 doped BaTiO3 based ceramic materials were investigated under different sintering conditions. Dielectric properties and microstructure of BaTio3 ceramics were significantly influenced by the addition of a small amount of Ta2O5. Dielectric properties were investigated by measuring the dielectric constant (k as a function of temperature and frequency. Percent theoretical density (%TD above 90 % was achieved for 0.5 and 1.0 mole %Ta2O5 doped BaTiO3. It was observed that the grain size decreased markedly above a doping concentration of 0.5 mole % Ta2O5. Although fine grain size down to 200 - 300 nm was attained, grain sizes in the range of 1-1.8µm showed the most alluring properties. The fine-grain quality and high density of the Ta2O5 doped BaTiO3 ceramic resulted in tenfold increase of dielectric constant. Stable value of dielectric constant as high as 13000 - 14000 was found in the temperature range of 55 to 80 °C, for 1.0 mole % Ta2O5 doped samples with corresponding shift of Curie point to ~82 °C. Experiments divulged that incorporation of a proper content of Ta2O5 in BaTiO3 could control the grain growth, shift the Curie temperature and hence significantly improve the dielectric property of the BaTiO3 ceramics.

  16. Dielectric Properties of CDS Nanoparticles Synthesized by Soft Chemical Route

    Indian Academy of Sciences (India)

    R Tripathi; A Kumar; T P Sinha

    2009-06-01

    CdS nanoparticles have been synthesized by a chemical reaction route using thiophenol as a capping agent. The frequency-dependent dielectric dispersion of cadmium sulphide (CdS) is investigated in the temperature range of 303–413 K and in a frequency range of 50 Hz–1 MHz by impedance spectroscopy. An analysis of the complex per-mittivity ( and ) and loss tangent (tan ) with frequency is performed by assuming a distribution of relaxation times. The scaling behaviour of dielectric loss spectra sug- gests that the relaxation describes the same mechanism at various temperatures. The frequency-dependent electrical data are analysed in the framework of conductivity and modulus formalisms. The frequency-dependent conductivity spectra obey the power law.

  17. [Reduction of dielectric properties of rat gastrocnemius induced by loss of weight].

    Science.gov (United States)

    Tang, Zhiynan; Zhao, Weihong; Wang, Lin; Ma, Qing

    2009-10-01

    In this experimental study, the AC impedance of isolated gastrocnemius was measured with an impendance analyzer of Agilent 4294A, and the effect of simulated weightlessness on the dielectric properties of the cells in isolated rat sural muscle was investigated by analyzing the dielectric numerical characters with the use of dielectric spectroscopy, the Cole-Cole plots, the spectrum of loss factor and loss tangent, as well as the spectrum of conductivity imaginary part. The results demonstrated that 10 weeks' simulated weightlessness caused some changes; for example, both permittivity at low frequency (epsilonL) and permittivity increment (deltaepsilon) were reduced, and conductivity at high frequency (kappa(h)) was also reduced; at the same time, conductivity increment (deltakappa) was reduced, too. The first characteristic frequency (f(C1)) decreased, while the second characteristic frequency(f(C2)) increased. All of the peak of loss factor, the peak of loss tangent, and the maximum of conductivity imaginary part were reduced. These data indicated that the reduction of dielectric properties of skeletal muscles was induced by weightlessness.

  18. Relaxor behavior and electrical properties of high dielectric constant materials

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    Several typical high dielectric constant materials are reviewed to study the electrical properties and relaxation mechanism. It is found that a Lorenz-type law can be used to describe the dielectric permit- tivity of either the normal ferroelectrics with or without diffuse phase transitions (DPT) or the typical ferroelectric relaxors. The ferroelectric DPT can be well described by just one fitting process using the Lorenz-type law, while the relaxor ferroelectric transition needs two independent fitting processes. The Lorenz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition. Above the transition temperature, the dielectric curves of all the studied materials can be well described by a Lorenz-type law.

  19. Relaxor behavior and electrical properties of high dielectric constant materials

    Institute of Scientific and Technical Information of China (English)

    FAN HuiQing; KE ShanMing

    2009-01-01

    Several typical high dielectric constant materials are reviewed to study the electrical properties and relaxation mechanism.It is found that a Lorenz-type law can be used to describe the dielectric permitUvity of either the normal ferroelectrics with or without diffuse phase transitions(DPT)or the typical ferroelectric relaxors.The ferroelectric DPT can be well described by just one fitting process using the Lorenz-type law,while the relaxor ferroelectric transition needs two independent fitting processes.The Lorenz-type law fails at the low temperature side of the dielectric maximum of a first-order ferroelectric phase transition.Above the transition temperature,the dielectric curves of all the studied materials can be well described by a Lorenz-type law.

  20. Temperature dependent dielectric and electric modulus properties of ZnS nano particles

    Science.gov (United States)

    Ali, Hassan; Falak, Attia; Rafiq, M. A.; Khan, Usman; Karim, Shafqat; Nairan, Adeela; Jing, Tang; Sun, Yue; Sun, Sibai; Qian, Chenjiang; Xu, Xiulai

    2017-03-01

    A comprehensive study of the dielectric and electric modulus properties of Zinc Sulfide (ZnS) semiconductor nanoparticles has been conducted using impedance spectroscopy in the frequency range of 200 Hz to 2 MHz and over the temperature range of 300 K to 400 K. Microscopic analysis confirms the formation of spherical nanoparticles with an average size of ∼20 nm. Maxwell–Wagner–Sillars (MWS) interfacial polarization is responsible for the increase in dielectric permittivity and dielectric loss at lower frequencies. Increase in dielectric permittivity and dielectric loss has been observed with a rise in temperature. The electric modulus complex plane plot reveals the presence of the grain (bulk) effect and non-Debye type relaxation processes in the material. The non-Debye type processes have also been confirmed by the asymmetric relaxation peaks of the imaginary part of the electric modulus. The frequency dependent maximum of the imaginary part of the electric modulus follows the Arrhenius law with an activation energy of 0.13 eV. The modulus analysis also establishes that the hopping mechanism is responsible for electrical conduction in the ZnS nanoparticles.

  1. Effect of high-pressure on calorimetric, rheological and dielectric properties of selected starch dispersions.

    Science.gov (United States)

    Ahmed, Jasim; Singh, Ajaypal; Ramaswamy, H S; Pandey, Pramod K; Raghavan, G S V

    2014-03-15

    Effects of high-pressure (HP) treatment on the rheological, thermal and dielectric properties of the four selected starch dispersions (two modified starches, one native and one resistant) were evaluated. Differential scanning calorimetry (DSC) and oscillatory rheometry were employed to assess the extent of starch gelatinization and the developed gel rigidity (G') of starch gels after HP treatment. It was observed that starch dispersions gelatinized completely at 500 MPa with a 30-min holding time. The HP-treated starch samples exhibited predominantly solid-like (G'>G") behavior except for the resistant starch. Pressure-induced gel rigidity differed significantly among starch samples. The G' of starch gels increased with the pressure (400-600 MPa) in the studied frequency range (0.1-10 Hz) except for the native starch where a marginal decrease was recorded at similar condition. The holding time (15-30 min) and concentration (20-25% w/w) significantly attributed towards gel rigidity of starch samples. Measurement of dielectric properties of HP-treated samples over the frequency range 450-4450 MHz indicated differences in the dielectric constant (ɛ'), loss factor (ɛ") and penetration depth among starch gels. Pressure did not show any effect on dielectric property of the resistant starch sample. Power penetration depth decreased significantly with frequency and with the pressure.

  2. Dielectric behaviors at microwave frequencies and Mössbauer effects of chalcedony, agate, and zultanite

    Science.gov (United States)

    Paralı, Levent; Şabikoǧlu, İsrafil; Tucek, Jiri; Pechousek, Jiri; Novak, Petr; Navarik, Jakub

    2015-05-01

    In this study, dielectric properties within 8-12 GHz microwave frequencies, inductively coupled plasma-atomic emission spectrometry, Fourier transform infrared spectrometry, synchronized two thermal analyses, and 57Fe Mössbauer spectroscopy analysis of chalcedony, agate, and zultanite samples from Turkey are presented. Agate and chalcedony show the same nine vibrational absorption peaks obtained unlike zultanite from FTIR spectra in the 350 cm-1 to 4000 cm-1 range, ɛ‧ values of chalcedony, agate and zultanite derived at 10.5 GHz were 4.67, 4.41, and 7.34, respectively, ɛ‧ and ɛ″ values of the studied samples at the microwave frequencies are related to the percentage weight of their constituent parts in their chemical compositions. 57Fe Mössbauer spectroscopy results confirm the existence of iron-containing islands in the crystal structure of zultanite, agate, and chalcedony samples, equipped them with magnetic features typical for magnetic nanoparticles including superparamagnetism. The presence of iron-containing islands significantly affects the magnetic, dielectric, and optical properties of studied samples that are not observed for pure minerals without any foreign inclusions. Project supported by the Project LO1305 and Operational Program Education for Competitiveness-European Social Fund of the Ministry of Education, Youth and Sports of the Czech Republic (Grant No. CZ.1.07/2.3.00/20.0155), and the Internal Student Grant IGA of Palacky University in Olomouc, Czech Republic (Grant No. IGA PrF 2014017).

  3. Dielectric parameters and a.c. conductivity of pure and doped poly (methyl methacrylate) films at microwave frequencies

    Indian Academy of Sciences (India)

    Anju Tanwar; K K Gupta; P J Singh; Y K Vijay

    2006-08-01

    Dielectric properties of pure and doped poly (methyl methacrylate) (PMMA) films at microwave frequency, 8.92 GHz, have been studied at 35°C. Iodine, benzoic acid and FeCl3 have been used as dopants. The losses in doped films are found to be larger than in pure PMMA films. The increased losses account for increased a.c. conductivity in doped films. The increase in conductivity is accounted due to creation of additional hopping sites for the charge carriers in doped samples. The dielectric data has also been used to evaluate optical constants, absorption index () and refractive index () of the films.

  4. Determination of Relationship between Dielectric Properties, Compressive Strength, and Age of Concrete with Rice Husk Ash Using Planar Coaxial Probe

    Directory of Open Access Journals (Sweden)

    Piladaeng Nawarat

    2016-02-01

    Full Text Available This paper deals with an investigation of the dielectric properties of concretes that includes rice husk ash using a planar coaxial probe. The planar coaxial probe has a planar structure with a microstrip and coaxial features. The measurement was performed over the frequency range of 0.5-3.5 GHz, and concrete specimens with different percentages of rice husk ash were tested. The results indicated that the dielectric constant of the concretes was inversely proportional to the frequency, while the conductivity was proportional to the frequency. The dielectric constant decreased with the increasing age of the concrete at the frequency of 1 GHz. The conductivity of the concrete decreased with the increasing age of the concrete at the frequency of 3.2 GHz. In addition, the dielectric constant and the conductivity decreased when the compressive strength increased. It was also shown that the obtained dielectric properties of the concrete could be used to investigate the relationship between the compressive strength and age of the concrete. Moreover, there is an opportunity to apply the proposed probe to determine the dielectric properties of other materials.

  5. Dielectric properties of inorganic fillers filled epoxy thin film

    Energy Technology Data Exchange (ETDEWEB)

    Norshamira, A., E-mail: myra.arshad@gmail.com; Mariatti, M., E-mail: mariatti@usm.my [School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, 14300 Nibong Tebal, Pulau Pinang (Malaysia)

    2015-07-22

    The demand on the small size and high performance electronics has driven changes in the electronic packaging requirements from discrete capacitor to embedded capacitor. Embedded capacitor can improve electrical performance compared with discrete capacitor. This study aimed to achieve high dielectric of epoxy thin film composite that were targeted for application as embedded capacitor. In this study, inorganic fillers such as Calcium Copper Titanate (CCTO), Iron(III) Oxide (Fe{sub 2}O{sub 3}) and Titanium Dioxide (TiO{sub 2}) were loaded in epoxy system at 5 and 20vol%. Morphology and dielectric properties were investigated to identify the effect of fillers loading and types of fillers on the properties of epoxy thin film composite. Based on the study, CCTO with 20vol% loading was found to have good dielectric properties compared to other type of fillers.

  6. Effect of Zr on dielectric, ferroelectric and impedance properties of BaTiO3 ceramic

    Indian Academy of Sciences (India)

    Sandeep Mahajan; O P Thakur; Chandra Prakash; K Sreenivas

    2011-12-01

    A polycrystalline sample of Zr-doped barium titanate (BaTiO3) was prepared by conventional solid state reaction method. The effect of Zr (0.15) on the structural and microstructural properties of BaTiO3 was investigated by XRD and SEM. The electrical properties (dielectric, ferroelectric and impedance spectroscopy) were measured in wide range of frequency and temperature. With substitutions of Zr, the structure of BaTiO3 changes from tetragonal to rhombohedral. Lattice parameters were found to increase with substitution. The room temperature dielectric constant increases from ∼ 1675 to ∼ 10586 and peak dielectric constant value increases from ∼ 13626 to ∼ 21023 with diffuse phase transition. Impedance spectroscopy reveals the formation of grain and grain boundary in the material and found to decrease with increase in temperature.

  7. Dielectric properties of tetragonal tungsten bronze films deposited by RF magnetron sputtering

    Science.gov (United States)

    Bodeux, Romain; Michau, Dominique; Josse, Michaël; Maglione, Mario

    2014-12-01

    Tetragonal tungsten bronze (TTB) films have been synthesised on Pt(111)/TiO2/SiO2/Si substrates from Ba2LnFeNb4O15 ceramics (Ln = La, Nd, Eu) by RF magnetron sputtering. X-ray diffraction measurements evidenced the multi-oriented nature of films with some degrees of preferential orientation along (111). The dependence of the dielectric properties on temperature and frequency has been investigated. The dielectric properties of the films are similar to those of the bulk, i.e., ɛ ˜150 and σ ˜10-6 Ω-1 cm-1 at 1 MHz and room temperature. The films exhibit two dielectric anomalies which are attributed to Maxwell Wagner polarization mechanism and relaxor behaviour. Both anomalies are sensitive to post-annealing under oxygen atmosphere and their activation energies are similar Ea ˜0.30 eV. They are explained in terms of electrically heterogeneous contributions in the films.

  8. Dielectric properties of residual water in amorphous lyophilized mixtures of sugar and drug

    Energy Technology Data Exchange (ETDEWEB)

    Moznine, R El [School of Pharmacy, De Montfort University, Leiceste (United Kingdom); Smith, G [School of Pharmacy, De Montfort University, Leicester (United Kingdom); Polygalov, E [School of Pharmacy, De Montfort University, Leicester (United Kingdom); Suherman, P M [School of Pharmacy, De Montfort University, Leicester (United Kingdom); Broadhead, J [AstraZeneca Charnwood R and D, Bakewell Rd, Loughborough (United Kingdom)

    2003-02-21

    Dielectric relaxation spectroscopy was used to investigate the properties of residual water in lyophilized formulations of a proprietary tri-phosphate drug containing a sugar (trehalose, lactose or sucrose) or dextran. The dielectric properties of each formulation were determined in the frequency range (0.1 Hz-0.1 MHz) and temperature range (30 deg. C-T{sub g}). The temperature dependence of the relaxation times for all samples showed Arrhenuis behaviour, from which the activation energy was derived. Proton hopping through the hydrogen-bonded network (clusters) of water molecules was suggested as the principle mode of charge transport. Significant differences in dielectric relaxation kinetics and activation energy were observed for the different formulations, which were found to correlate with the amount of monophosphate degradation product.

  9. Dielectric spectroscopy of water at low frequencies: The existence of an isopermitive point

    CERN Document Server

    Angulo-Sherman, A

    2010-01-01

    We have studied the real part of the dielectric constant of water from 100 Hz to 1 MHz. We have found that there is a frequency where the dielectric constant is independent of temperature, and called this the isopermitive point. Below this point the dielectric constant increases with temperature, above, it decreases. To understand this behavior, we consider water as a system of two species: ions and dipoles. The first give rise to the so called Maxwell-Wagner-Sillars effect, the second obey the Maxwell-Boltzmann statistics. At the isopermitive point the effect of both mechanisms in the dielectric response compensate each other.

  10. A Novel Technology for Measurements of Dielectric Properties of Extremely Small Volumes of Liquids

    Directory of Open Access Journals (Sweden)

    Wei-Na Liu

    2016-01-01

    Full Text Available A high sensitivity sensor for measurement radio frequency (RF dielectric permittivity of liquids is described. Interference is used and parasitic effects are cancellation, which makes the sensor can catch weak signals caused by liquids with extremely small volumes. In addition, we present the relationship between transmission coefficient and permittivity of liquids under test (LUT. Using this sensor, quantitative measurements of the dielectric properties at 5.8 GHz are demonstrated of LUTs. Experiments show that the proposed method only requires the volume of 160 nanoliters for liquids. Therefore, the technology can be used for RF spectroscopic analysis of biological samples and extremely precious liquids.

  11. Influence of La2O3 Additions on Chemical Durability and Dielectric Properties of Boroaluminosilicate Glasses

    Science.gov (United States)

    Zhang, X. H.; Yue, Y. L.; Wu, H. T.

    2012-12-01

    Boroaluminosilicate glasses containing La2O3 were prepared by the normal quenching method. The glass transition temperatures (Tg) were measured by differential scanning calorimetry (DSC). The structural role of RO was investigated by nuclear magnetic resonance (NMR). Chemical durability was evaluated by weight losses of glass samples after immersion in HC1 solution. High resolution scanning electron microscopy (HR-SEM) was used to examine the surface micrographs of corroded glass samples. The dielectric constant and tangent loss were measured in the frequency range 10-106 Hz. The results revealed that chemical durability and dielectric properties increased with increasing La2O3 content.

  12. Study of optical and dielectric properties of annealed ZnO nanoparticles in the terahertz regime

    Institute of Scientific and Technical Information of China (English)

    WANG Ming-wei; Boon Kuan Woo; TIAN Zhen; HAN Jia-guang; CHEN Wei; ZHANG Wei-li

    2009-01-01

    The frequency-dependent optical and dielectric properties of annealed ZnO nanoparticles in the range of 0.1 to 0.9 THz are studied by using terahertz time-domain spectroscopy (THz-TDS). The refractive index, power absorption and complex dielectric constants are obtained and the experimental results are well fit with a simple effective medium theory in conjunc-tion with a pseudo-harmonic model. This study reveals that annealed ZnO nanoparticles exhibit the similar phonon response characteristics to the single ZnO crystal and other ZnO nanostructures, such as tetrapods and nanowires.

  13. EFFECTS OF NEODYMIUM DOPING ON DIELECTRIC AND OPTICAL PROPERTIES OF Ba(1-xNdxTi1.005O3 CERAMICS

    Directory of Open Access Journals (Sweden)

    Zhang W.

    2013-06-01

    Full Text Available This paper investigated the optical properties and dielectric properties of neodymium doped BaTiO3 ceramics prepared by Ba(1-xNdxTi1.005O3 powders synthesized via a hydrothermal method. The effects of Nd3+ ions content on the structure, dielectric properties and optical properties of the ceramics were studied. The structural analysis performed on the X-ray diffractometer shows that the phase compositions of all ceramics are tetragonal phase structure. The red shift of the absorption edge indicates the presence of defect energy levels which was proved by the UV-Vis-NIR diffuse reflection spectra. Dielectric property measurements show that Nd-doped BaTiO3 ceramics possess improved dielectric properties at low Nd3+ contents (x = 0.001 and 0.002, as demonstrated by decreased dependence to frequency for both the dielectric constant and dielectric loss.

  14. Preparation of a Carbon Doped Tissue-Mimicking Material with High Dielectric Properties for Microwave Imaging Application

    Directory of Open Access Journals (Sweden)

    Siang-Wen Lan

    2016-07-01

    Full Text Available In this paper, the oil-in-gelatin based tissue-mimicking materials (TMMs doped with carbon based materials including carbon nanotube, graphene ink or lignin were prepared. The volume percent for gelatin based mixtures and oil based mixtures were both around 50%, and the doping amounts were 2 wt %, 4 wt %, and 6 wt %. The effect of doping material and amount on the microwave dielectric properties including dielectric constant and conductivity were investigated over an ultra-wide frequency range from 2 GHz to 20 GHz. The coaxial open-ended reflection technology was used to evaluate the microwave dielectric properties. Six measured values in different locations of each sample were averaged and the standard deviations of all the measured dielectric properties, including dielectric constant and conductivity, were less than one, indicating a good uniformity of the prepared samples. Without doping, the dielectric constant was equal to 23 ± 2 approximately. Results showed with doping of carbon based materials that the dielectric constant and conductivity both increased about 5% to 20%, and the increment was dependent on the doping amount. By proper selection of doping amount of the carbon based materials, the prepared material could map the required dielectric properties of special tissues. The proposed materials were suitable for the phantom used in the microwave medical imaging system.

  15. Comparison dielectric and thermal properties of polyurethane/organoclay nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Baysal, Gülay [Department of Chemistry, University of Dicle, Diyarbakır 21280 (Turkey); Aydin, Haluk, E-mail: halukaydin@dicle.edu.tr [Department of Chemistry, University of Dicle, Diyarbakır 21280 (Turkey); Köytepe, Süleyman; Seçkin, Turgay [Department of Chemistry, University of Inonu, Malatya 44280 (Turkey)

    2013-08-20

    Highlights: • The PU/organoclay composites was successfully obtained by mixing method from solution. • The growth temperature does not exceed 60 °C in any step of the modification and drying. • PU-IL-Mt modified with IL showed power alternative to PU-QAS-Mt modified with QAS. • The PU composites exhibited better thermal stability and lower dielectric constants than the pure PU. - Abstract: Polyurethane composites were obtained with different organoclay contents. The organoclay Na{sup +}-montmorillonite was dispersed in the PU matrix by mixing method from solution. Na{sup +}-montmorillonite was modified with dodecyl ammonium sulphate and 1-methyl-3-octyl imidazolium tetrafluoroborate. The nanocomposites obtained by using different modifier were compared in terms of dielectric and thermal properties. The dispersion state of the organoclay particles and its effect on the thermogravimetric and dielectric properties of the composites was investigated. The characterization of PU/organooclay composites was carried out by means of scanning electron microscopy, Fourier transform infrared, thermogravimetric analysis and X-ray diffraction. The dielectric properties of the PU/organoclay nanocomposites were studied in detail. The obtained PU/organoclay intercalated nanocomposites exhibited better thermal stability and improved lower dielectric constants than the pure PU.

  16. Dielectric Properties of Polyvinyl Alcohol, Poly(methyl Methacrylate), Polyvinyl Butyral Resin and Polyimide at Low Temperatures

    Science.gov (United States)

    Tuncer, Enis; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.

    2008-03-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI-Kapton®). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45 K to 350 K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and PMMA dissolved in toluene have the lowest dielectric losses for temperatures lower than 100 K. PVB and PI have the smallest spread in their breakdown strength data.

  17. DIELECTRIC PROPERTIES OF POLYVINYL ALCOHOL, POLY(METHYL METHACRYLATE), POLYVINYL BUTYRAL RESIN AND POLYIMIDE AT LOW TEMPERATURES

    Energy Technology Data Exchange (ETDEWEB)

    Tuncer, Enis [ORNL; Sauers, Isidor [ORNL; James, David Randy [ORNL; Ellis, Alvin R [ORNL

    2008-01-01

    Performance of materials and their compatibility determine the size of the electrical insulation in power equipment. For this reason dielectric properties of electrical insulation materials are needed for low temperature power applications. In this work we report the dielectric properties of four polymers: polyvinyl alcohol (PVA), poly(methyl methacrylate) (PMMA), polyvinyl butyral resin (PVB), and polyimide (PI--Kapton\\textregistered). The dielectric measurements are performed with an electrical impedance analyzer in the frequency domain. The impedances are recorded in a cryocooler in the temperature range from 45K to 350K. The dielectric breakdown characteristics of the polymers are measured in a liquid nitrogen bath at atmospheric pressure. It is observed that PI and \\pmma\\ dissolved in toluene have the lowest dielectric losses for temperatures lower than $100\\ \\kelvin$. \\Blx\\ and PI have the smallest spread in their breakdown strength data.

  18. Combinatorial Frequency Generation in Quasi-Periodic Stacks of Nonlinear Dielectric Layers

    Directory of Open Access Journals (Sweden)

    Oksana Shramkova

    2014-07-01

    Full Text Available Three-wave mixing in quasi-periodic structures (QPSs composed of nonlinear anisotropic dielectric layers, stacked in Fibonacci and Thue-Morse sequences, has been explored at illumination by a pair of pump waves with dissimilar frequencies and incidence angles. A new formulation of the nonlinear scattering problem has enabled the QPS analysis as a perturbed periodic structure with defects. The obtained solutions have revealed the effects of stack composition and constituent layer parameters, including losses, on the properties of combinatorial frequency generation (CFG. The CFG features illustrated by the simulation results are discussed. It is demonstrated that quasi-periodic stacks can achieve a higher efficiency of CFG than regular periodic multilayers.

  19. Dielectric characterization of healthy and malignant colon tissues in the 0.5-18 GHz frequency band

    Science.gov (United States)

    Fornes-Leal, A.; Garcia-Pardo, C.; Frasson, M.; Pons Beltrán, V.; Cardona, N.

    2016-10-01

    Several reports over the last few decades have shown that the dielectric properties of healthy and malignant tissues of the same body organ usually show different values. However, no intensive dielectric studies of human colon tissue have been performed, despite colon cancer’s being one of the most common types of cancer in the world. In order to provide information regarding this matter, a dielectric characterization of healthy and malignant colon tissues is presented. Measurements are performed on ex vivo surgery samples obtained from 20 patients, using an open-ended coaxial probe in the 0.5-18 GHz frequency band. Results show that the dielectric constant of colon cancerous tissue is 8.8% higher than that of healthy tissues (p  =  0.002). Besides, conductivity is about 10.6% higher, but in this case measurements do not have statistical significance (p  =  0.038). Performing an analysis per patient, the differences in dielectric constant between healthy and malignant tissues appear systematically. Particularized results for specific frequencies (500 MHz, 900 MHz, 2.45 GHz, 5 GHz, 8.5 GHz and 15 GHz) are also reported. The findings have potential application in early-stage cancer detection and diagnosis, and can be useful in developing new tools for hyperthermia treatments as well as creating electromagnetic models of healthy and cancerous tissues.

  20. On the Dielectric and Magnetic Properties of Nanocomposites

    Directory of Open Access Journals (Sweden)

    B. Hallouet

    2007-01-01

    Full Text Available We investigate nanocomposites, that is, dispersions of magnetite nanoparticles in an epoxy resin, by means of broadband dielectric and magnetic spectroscopy. The molecular dynamics of the polymer matrix is altered by the nanoparticles. Due to the formation of agglomerates neither permittivity nor permeability can be described with known effective medium models. We use the spectral representation (Bergman theorem to show that a model-free evaluation of the low-frequency permeability of the nanoparticles can be achieved by combining dielectric and magnetic data. In addition, the ferromagnetic resonance is studied experimentally. It occurs near 3 GHz and is independent of the particle concentration.

  1. Dielectric properties of novel polyurethane/silica nanowire composites.

    Science.gov (United States)

    Kim, Mu-Seong; Sekhar, Praveen K; Bhansali, Shekhar; Harmon, Julie P

    2009-10-01

    An aliphatic isocyanate, polyether, polyol thermoplastic polyurethane, Tecoflex SG-85A, was solution processed with the varying amounts of silica nanowire. The dielectric permittivity (epsilon') and loss factor (epsilon") were measured via Dielectric Analysis (DEA) in the frequency range 1 Hz to 100 kHz and between the temperature -150 to 150 degrees C. The electric modulus formalism was used to reveal alpha, beta and conductivity relaxations. The activation energies for the relaxations are presented. Nanocomposites were also characterized by differential scanning calorimetry (DSC) to determine glass transition temperatures. The onset of decomposition temperature was measured by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) provided images of the polymer-nanocomposites.

  2. Real space electrostatics for multipoles. III. Dielectric Properties

    CERN Document Server

    Lamichhane, Madan; Newman, Kathie E; Gezelter, J Daniel

    2016-01-01

    In the first two papers in this series, we developed new shifted potential (SP), gradient shifted force (GSF), and Taylor shifted force (TSF) real-space methods for multipole interactions in condensed phase simulations. Here, we discuss the dielectric properties of fluids that emerge from simulations using these methods. Most electrostatic methods (including the Ewald sum) require correction to the conducting boundary fluctuation formula for the static dielectric constants, and we discuss the derivation of these corrections for the new real space methods. For quadrupolar fluids, the analogous material property is the quadrupolar susceptibility. As in the dipolar case, the fluctuation formula for the quadrupolar susceptibility has corrections that depend on the electrostatic method being utilized. One of the most important effects measured by both the static dielectric and quadrupolar susceptibility is the ability to screen charges embedded in the fluid. We use potentials of mean force between solvated ions to...

  3. Simulation of the frequency dispersion of effective dielectric characteristics of composite materials

    Energy Technology Data Exchange (ETDEWEB)

    Yakovlev, V. B.; Bardushkin, V. V.; Lavrov, I. V., E-mail: iglavr@mail.ru; Yakovleva, E. N. [National Research University of Electronic Technology (MIET) (Russian Federation)

    2014-12-15

    The problems of calculating the effective dielectric characteristics of polycrystalline materials are considered taking into account the frequency dependence of the characteristics of individual components. The effective characteristics of ceramics such as lead zirconate-titanate with titanium and zirconium oxide, metal lead, and water inclusions are calculated in the Maxwell-Garnett and Bruggeman approximations. The dependences of the effective dielectric characteristics on the inclusion concentration and applied electromagnetic-field frequency are obtained.

  4. Piezoelectric, dielectric, and ferroelectric properties of 0-3 ceramic/cement composites

    Science.gov (United States)

    Xin, Cheng; Shifeng, Huang; Jun, Chang; Zongjin, Li

    2007-05-01

    The sulphoaluminate cement and a piezoelectric ceramic, 0.08Pb(Li1/4Nb3/4)O3.0.47PbTiO3.0.45PbZrO3[P(LN)ZT], were used to fabricate 0-3 cement based piezoelectric composites. The piezoelectric, dielectric, and ferroelectric properties of the composites were mainly investigated. The results indicate that the piezoelectric strain factor d33 increases as the P(LN)ZT volume fraction increases, which follows the cube model well. The dielectric constant ɛx and dielectric loss tan δ show similar trends with the d33. In the frequency range of 40-100 kHz, the dielectric constants of the composites decrease sharply, which is mainly attributed to interfacial polarization in the composite. Above 200 kHz, the cement-based piezoelectric composites exhibit good dielectric-frequency stability. Hysteresis measurements indicate that the composites exhibit typical ferroelectric hysteresis loops at room temperature. The remanent polarization Pr and the coercive field Ec of the composites increase as the P(LN)ZT volume fraction increases. Meanwhile, the remnant polarizations Pr shows little asymmetric characterization.

  5. Preparation, Structural and Dielectric Properties of Solution Grown Polyvinyl Alcohol(PVA) Film

    Science.gov (United States)

    Nangia, Rakhi; Shukla, Neeraj K.; Sharma, Ambika

    2017-08-01

    Flexible dielectrics with high permittivity have been investigated extensively due to their applications in electronic industry. In this work, structural and electrical characteristics of polymer based film have been analysed. Poly vinyl alcohol (PVA) film was prepared by solution casting method. X-ray diffraction (XRD) characterization technique is used to investigate the structural properties. The semi-crystalline nature has been determined by the analysis of the obtained XRD pattern. Electrical properties of the synthesized film have been analysed from the C-V and I-V curves obtained at various frequencies and temperatures. Low conductivity values confirm the insulating behaviour of the film. However, it is found that conductivity increases with temperature. Also, the dielectric permittivity is found to be higher at lower frequencies and higher temperatures, that proves PVA to be an excellent dielectric material which can be used in interface electronics. Dielectric behaviour of the film has been explained based on dipole orientations to slow and fast varying electric field. However further engineering can be done to modulate the structural, electrical properties of the film.

  6. Structural and dielectric properties of phosphorous-doped PLZT ceramics

    Indian Academy of Sciences (India)

    Puja Goel; Subhash Sharma; Kanhaiya Lal Yadav; Ajit Ram James

    2005-12-01

    In the present work we have reported the unique effects of P2O5-doped PLZT ceramics with composition (Pb0.92La0.08)(Zr0.65Ti0.35)O3 + wt% of P2O5 (where = 1, 3 and 5) prepared chemically by co-precipitation method. X-ray diffraction studies suggest that the prepared compound was very fine (10–25 nm), homogeneous and of rhombohedral symmetry. The apparent density of samples decreased with the P5+ additions. Studies of dielectric constant and dielectric loss as a function of frequency (10–1000 kHz) and temperature suggest that the compound undergoes diffuse type of phase transition without any sign of relaxor behaviour. With increasing , dielectric constant was found to decrease appreciably, whereas Curie temperature (C) was found to increase.

  7. Dielectric properties of PMMA-SiO2 hybrid films

    KAUST Repository

    Morales-Acosta, M. D.

    2010-03-01

    Organic-inorganic hybrid films were synthesized by a modified sol-gel process. PMMASiO2 films were prepared using methylmethacrylate (MMA), tetraethil-orthosilicate (TEOS) as silicon dioxide source, and 3-trimetoxi-silil-propil-methacrylate (TMSPM) as coupling agent. FTIR measurements were performed on the hybrid films to confirm the presence of PMMA-SiO2 bonding. In addition, metal-insulator-metal (MIM) devices were fabricated to study the dielectric constant of the films as function of frequency (1 KHz to 1 MHz). Electrical results show a weak trend of the dielectric constant of the hybrid films with MMA molar ratio. More importantly, the PMMA-SiO2 hybrid films showed a higher dielectric constant than SiO2 and PMMA layers, which is likely due to the presence of additional C-O-C bond. © (2010) Trans Tech Publications.

  8. Low-Frequency Dielectric Dispersion of Highly Concentrated Spherical Particles in an Electrolyte Solution

    Institute of Scientific and Technical Information of China (English)

    倪福生; 顾国庆; 陈康民

    2002-01-01

    We deal with the problem of calculating the effective dielectric dispersion and electrical conductivity of colloidaldispersions. A comparison of the theoretical calculation of first principles with the experimental data of Schwanshows that our technique proposed here is no longer restricted to dilute solutions and is very effective for studyingthe dielectric properties of colloids with highly concentrated charged spherical particles in an electrolyte solution.

  9. Monitoring Coaxial-Probe Contact Force for Dielectric Properties Measurement

    Science.gov (United States)

    A means is described for measuring and monitoring the contact force applied to a material sample with an open-ended coaxial-line probe for purposes of measuring the dielectric properties of semisolid material samples such as fruit, vegetable and animal tissues. The equipment consists of a stainless...

  10. A Comprehensive Study on Dielectric Properties of Volcanic Rock/PANI Composites

    Science.gov (United States)

    Kiliç, M.; Karabul, Y.; Okutan, M.; İçelli, O.

    2016-05-01

    Basalt is a very well-known volcanic rock that is dark colored and relatively rich in iron and magnesium, almost located each country in the world. These rocks have been used in the refused rock industry, to produce building tiles, construction industrial, highway engineering. Powders and fibers of basalt rocks are widely used of radiation shielding, thermal stability, heat and sound insulation. This study examined three different basalt samples (coded CM-1, KYZ-13 and KYZ-24) collected from different regions of Van province in Turkey. Polyaniline (PANI) is one of the representative conductive polymers due to its fine environmental stability, huge electrical conductivity, as well as a comparatively low cost. Also, the electrical and thermal properties of polymer composites containing PANI have been widely studied. The dielectric properties of Basalt/Polyaniline composites in different concentrations (10, 25, 50 wt.% PANI) have been investigated by dielectric spectroscopy method at the room temperature. The dielectric parameters (dielectric constants, loss and strength) were measured in the frequency range of 102 Hz-106 Hz at room temperature. The electrical mechanism change with PANI dopant. A detailed dielectrically analysis of these composites will be presented.

  11. Effect of argon ion implantation on the electrical and dielectric properties of CR-39

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, Mahak, E-mail: mahak.chawla@gmail.com; Shekhawat, Nidhi; Goyal, Meetika; Gupta, Divya; Sharma, Annu; Aggarwal, Sanjeev [Department of Physics, Kurukshetra University, Kurukshetra - 136119 (India)

    2016-05-23

    The objective of the present work is to study the effect of 130 keV Ar{sup +} ions on the electrical and dielectric properties of CR-39 samples at various doses 5×10{sup 14}, 1×10{sup 15} and 1×10{sup 16} Ar{sup +} cm{sup −2}. Current-Voltage (I-V characteristics) measurements have been used to study the electrical properties of virgin and Ar{sup +} implanted CR-39 specimens. The current has been found to be increased with increasing voltage as well as with increasing ion dose. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. The dielectric constant has been found to be decreasing whereas dielectric loss factor increases with increasing ion fluence. These kind of behavior observed in the implanted specimens indicate towards the formation of carbonaceous clusters due to the cross linking, chemical bond cleavage, formation of free radicals. The changes observed in the dielectric behavior have been further correlated with the structural changes observed through I-V characteristics.

  12. Effect of argon ion implantation on the electrical and dielectric properties of CR-39

    Science.gov (United States)

    Chawla, Mahak; Shekhawat, Nidhi; Goyal, Meetika; Gupta, Divya; Sharma, Annu; Aggarwal, Sanjeev

    2016-05-01

    The objective of the present work is to study the effect of 130 keV Ar+ ions on the electrical and dielectric properties of CR-39 samples at various doses 5×1014, 1×1015 and 1×1016 Ar+ cm-2. Current-Voltage (I-V characteristics) measurements have been used to study the electrical properties of virgin and Ar+ implanted CR-39 specimens. The current has been found to be increased with increasing voltage as well as with increasing ion dose. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. The dielectric constant has been found to be decreasing whereas dielectric loss factor increases with increasing ion fluence. These kind of behavior observed in the implanted specimens indicate towards the formation of carbonaceous clusters due to the cross linking, chemical bond cleavage, formation of free radicals. The changes observed in the dielectric behavior have been further correlated with the structural changes observed through I-V characteristics.

  13. Local Electronic And Dielectric Properties at Nanosized Interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Bonnell, Dawn A. [Univ. of Pennsylvania, Philadelphia, PA (United States)

    2015-02-23

    Final Report to the Department of Energy for period 6/1/2000 to 11/30/2014 for Grant # DE-FG02-00ER45813-A000 to the University of Pennsylvania Local Electronic And Dielectric Properties at Nanosized Interfaces PI: Dawn Bonnell The behavior of grain boundaries and interfaces has been a focus of fundamental research for decades because variations of structure and composition at interfaces dictate mechanical, electrical, optical and dielectric properties in solids. Similarly, the consequence of atomic and electronic structures of surfaces to chemical and physical interactions are critical due to their implications to catalysis and device fabrication. Increasing fundamental understanding of surfaces and interfaces has materially advanced technologies that directly bear on energy considerations. Currently, exciting developments in materials processing are enabling creative new electrical, optical and chemical device configurations. Controlled synthesis of nanoparticles, semiconducting nanowires and nanorods, optical quantum dots, etc. along with a range of strategies for assembling and patterning nanostructures portend the viability of new devices that have the potential to significantly impact the energy landscape. As devices become smaller the impact of interfaces and surfaces grows geometrically. As with other nanoscale phenomena, small interfaces do not exhibit the same properties as do large interfaces. The size dependence of interface properties had not been explored and understanding at the most fundamental level is necessary to the advancement of nanostructured devices. An equally important factor in the behavior of interfaces in devices is the ability to examine the interfaces under realistic conditions. For example, interfaces and boundaries dictate the behavior of oxide fuel cells which operate at extremely high temperatures in dynamic high pressure chemical environments. These conditions preclude the characterization of local properties during fuel cell

  14. Microwave Dielectric Properties of Polystyrene-Forsterite (Mg2SiO4) Composite

    Science.gov (United States)

    Sasikala, T. S.; Sebastian, M. T.

    2016-01-01

    Polystyrene-Mg2SiO4 ceramic composites have been prepared by kneading followed by hot pressing. The dielectric properties of the composites have been investigated at both radio and microwave frequency ranges as a function of filler loading up to 50 vol.%. The dielectric constant and loss tangent increased with the ceramic filler content. The composite with 50 vol.% filler had a dielectric constant of 4.0 and loss tangent of 0.006 at 5 GHz, with Vickers microhardness of 35 HV. The coefficient of thermal expansion of the composite decreased and the thermal conductivity increased with the filler loading. PS-Mg2SiO4 composites are possible candidates for microwave substrate applications.

  15. Electronic, mechanical and dielectric properties of silicane under tensile strain

    Energy Technology Data Exchange (ETDEWEB)

    Jamdagni, Pooja, E-mail: j.poojaa1228@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla, Himachal Pradesh, India 171005 (India); Kumar, Ashok [Physics Department, Panjab University, Chandigarh, India, 160014 (India); Thakur, Anil [Physics Department, Govt. Collage Solan, Himachal Pradesh, India,173212 (India)

    2015-05-15

    The electronic, mechanical and dielectric properties of fully hydrogenated silicene i.e. silicane in stable configuration are studied by means of density functional theory based calculations. The band gap of silicane monolayer can be flexibly reduced to zero when subjected to bi-axial tensile strain, leading to semi-conducting to metallic transition, whereas the static dielectric constant for in-plane polarization increases monotonically with increasing strain. Also the EEL function show the red shift in resonance peak with tensile strain. Our results offer useful insight for the application of silicane monolayer in nano-optical and electronics devices.

  16. Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics

    KAUST Repository

    Li, Yangyang

    2013-05-01

    The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid

  17. Dielectric and relaxation properties of poly(o-anisidine)/graphene nanocomposite

    Science.gov (United States)

    Sangamithirai, D.; Narayanan, V.; Stephen, A.

    2016-05-01

    Poly(o-anisidine)/graphene (POA/GR) nanocomposite was synthesized via chemical oxidative polymerization of o-anisidine in the presence of graphene sheets in acidic medium. The electrical properties of the nanocomposite are studied using AC impedance spectroscopic technique. It has been found that the room temperature electrical conductivity value enhanced from 1.28 × 10-6 S cm-1 to 4.47 × 10-4 S cm-1 on addition of 10 wt % of graphene into the polymer. An analysis of real and imaginary parts of dielectric permittivity reveals that both ɛ` and ɛ״ increases with the decrease of frequency at all temperature levels. Frequency dependence of dielectric loss (tan δ) spectrum indicates that hopping frequency increases with temperature and the relaxation time decreases from 2.67 × 10-5 to 7.28 × 10-6 sec.

  18. Analysis of a shielded TE011 mode composite dielectric resonator for stable frequency reference

    Indian Academy of Sciences (India)

    N D Kataria; K S Daya; V G Das

    2002-05-01

    Analysis of a TE011 mode composite sapphire–rutile dielectric resonator has been carried out to study the temperature variation of resonance frequency, close to the Cs atomic clock hyperfine frequency of 9.192 GHz. The complementary behavior of dielectric permittivity with temperature of the composite has been exploited to obtain the desired turning point in the resonant frequency. The frequency of the composite structure is found to be independent of the shield diameter beyond four times the puck diameter.

  19. Investigation of dielectric properties of La0.33NbO3 ceramics

    Science.gov (United States)

    Mondal, Tanusree; Sarun, P. M.; Das, Sayantani; Sinha, T. P.

    2015-06-01

    La0.33NbO3 ceramics was prepared via conventional solid-state reaction method. Structural analysis show the existence of single phase of La0.33NbO3 has been synthesized with an average particle size of 2 µm - 4 µm estimated from FESEM image. Detailed investigation on the dielectric properties and AC conductivity of the La0.33NbO3 ceramics in a wide range of frequency (800 Hz - 5 MHz) and temperatures (30 °C - 300 °C) revealed that these properties are strongly temperature and frequency dependent.

  20. Dielectric Properties of Ice-Water Systems: Laboratory Characterization and Modeling

    Science.gov (United States)

    West, J.; Rippin, D. M.; Endres, A. L.; Murray, T.

    2005-05-01

    Glacier mechanical properties, and hence their response to climatic change, depend strongly on the proportion and distribution of unfrozen water at ice grain boundaries. Glaciologists have characterized unfrozen water content in several ways, notably via thin section microscopic analysis of ice cores to measure porewater contents, and field surveys of electromagnetic properties using radar. Water content has a very strong influence on the velocity of electromagnetic (radar) waves in ice, because of the high dielectric constant of water (~80) in comparison with ice (~3). However, there is a strong discrepancy between the two methods of measurement, with field radar surveys on glaciers giving unfrozen water contents of several volumetric percent, whereas ice-core microscopy gives values of less than one percent. This discrepancy has called into question the approach used to obtain the unfrozen water content from radar wave velocity. This approach assumes that the ice-water mixture is a lossless medium. Here, we report a laboratory and modeling based investigation of the relationship between dielectric properties and unfrozen water content of ice cores from the Glacier de Tsanfleuron, Switzerland, aimed at resolving the discrepancy. The laboratory study uses the technique of Time Domain Reflectometry to characterize the dielectric properties of ice cores from a range of ice facies. `Press on' TDR waveguides have been developed specifically for use on ice cores. Several press-on probe designs have been developed and aspects of their performance are reported. An independent estimate of unfrozen water content is determined from temperature and total pore fluid ionic strength. The results allow the establishment of relationships between the high frequency (~500MHz) dielectric properties and water content for various ice-crystal geometries. Mathematical modeling of the dependence of dielectric constant on frequency and water phase conductivity has been undertaken using

  1. Dielectric properties of hybrid perovskites and drift-diffusion modeling of perovskite cells

    OpenAIRE

    Pedesseau, Laurent; Kepenekian, M.; Sapori, Daniel; Huang, Y.; Rolland, Alain; Beck, Alexandre; C. Cornet; Durand, Olivier; Wang, Shijian; Katan, Claudine; Even, Jacky

    2016-01-01

    International audience; A method based on DFT is used to obtained dielectric profiles. The high frequency ε∞(z) and the static εs(z) dielectric profiles are compared for 3D, 2D-3D and 2D Hybrid Organic Perovskites (HOP). A dielectric confinement is observed for the 2D materials between the high dielectric constant of the inorganic part and the low dielectric constant of the organic part. The effect of the ionic contribution on the dielectric constant is also shown. The quantum and dielectric ...

  2. Dielectric properties of BST/MZO ceramic composites

    Institute of Scientific and Technical Information of China (English)

    GUI JianDong; WANG Yi; DONG GuiXia; DU Jun

    2009-01-01

    Ba0.6Sr0.4TiO3/Mg1-xZnxO (MZO, x = 0, 0.05, 0.10, 0.15 and 0.20) ceramic composites were prepared by traditional ceramic processing. The crystal structure, fracture surface morphology, and dielectric properties were investigated. The samples with x = 0, 0.05 and 0.10 exhibited favorable sintering be-havior, and homogeneous diphase microstructure was obtained. Nevertheless, the microstructure of the samples with x = 0.15 and 0.20 was inhomogeneous and abnormal grain growth could be observed, and the abnormal grain growth induced the degradation of dielectric strength. The sample with x = 0.10 has relatively low dielectric loss (1.26×10-3) and the optimal FOM value (about 174).

  3. Dielectric properties of nanocrystalline Co-Mg ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Jyoti, E-mail: jyotijoshi.phy2008@gmail.com [Department of Physics, University of Rajasthan, Jaipur (India); Sharma, Neha [Department of Physics, VEC Lakhanpur, Sarguja University, Ambikapur (C.G.) (India); Parashar, Jyoti; Saxena, V.K.; Bhatnagar, D. [Department of Physics, University of Rajasthan, Jaipur (India); Sharma, K.B. [Department of Physics, S. S. Jain Subodh P. G. College, Jaipur (India)

    2015-11-15

    Nanocrystalline powder samples with chemical formula Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} (x = 0, 0.2, 0.4, 0.6, 0.8 and 1.0) have been synthesized by sol–gel auto combustion method using citric acid as fuel agent. The rietveld refinement study of x-ray diffraction patterns confirmed the spinel single phase formation for all samples. Dielectric constant (ε′), dielectric loss tangent (tan δ) and AC conductivity of Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} ferrite nanoparticles have been measured at room temperature in the frequency range from 1000 Hz to 120 MHz. The dielectric dispersion observed at lower frequency region is attributed to Maxwell–Wagner two layer model, which is in agreement with Koops phenomenological theory. The observed results have been explained by polarization which is attributed to the electron exchange between Fe{sup 2+} and Fe{sup 3+} ions. The temperature variation of ε′ and tanδ for some particular frequencies were studied. The rapid increase in ε′ and tan δ has been explained using thermally activated electron exchange between Fe{sup 2+} ↔ Fe{sup 3+} and Co{sup 2+} ↔ Co{sup 3+} ions at adjacent octahedral sites. The role of interfacial polarization has been focused to explain the high dispersion in ε′ and tanδ with temperature observed at low frequencies. - Graphical abstract: (a) TEM image of Co{sub 0.4}Mg{sub 0.6}Fe{sub 2}O{sub 4} shows the nano size of the synthesized ferrite particles and (b) Dielectric constant behavior with frequency of Co{sub x}Mg{sub 1−x}Fe{sub 2}O{sub 4} ferrite.

  4. A comparison between leaf dielectric properties of stressed and unstressed tomato plants

    NARCIS (Netherlands)

    Van Emmerik, T.H.M.; Steele-Dunne, S.C.; Judge, J.; Van de Giesen, N.C.

    2015-01-01

    Leaf dielectric properties influence microwave scattering from a vegetation canopy. The dielectric properties of leaves are primarily a function of leaf water content. Understanding the effect of water stress on leaf dielectric properties will give insight in how plant dynamics change as a result of

  5. A comparison between leaf dielectric properties of stressed and unstressed tomato plants

    NARCIS (Netherlands)

    Van Emmerik, T.H.M.; Steele-Dunne, S.C.; Judge, J.; Van de Giesen, N.C.

    2015-01-01

    Leaf dielectric properties influence microwave scattering from a vegetation canopy. The dielectric properties of leaves are primarily a function of leaf water content. Understanding the effect of water stress on leaf dielectric properties will give insight in how plant dynamics change as a result of

  6. Dielectric properties of isolated clusters beam deflection studies

    CERN Document Server

    Heiles, Sven

    2013-01-01

    A broad range of state-of-the-art methods to determine properties of clusters are presented. The experimental setup and underlying physical concepts of these experiments are described. Furthermore, existing theoretical models to explain the experimental observations are introduced and the possibility to deduce structural information from measurements of dielectric properties is discussed. Additional case studies are presented in the book to emphasize the possibilities but also drawbacks of the methods.

  7. Electrophysical properties of microalloyed alumo-silicate ceramics as active dielectric

    Directory of Open Access Journals (Sweden)

    Purenović Jelena

    2013-01-01

    Full Text Available In this paper, electrophysical properties of porous alumo-silicate ceramics, modified by alloying with magnesium and microalloying with aluminum, were investigated. Complex multiphase system, as active microalloyed ceramics, has specific behavior under influence of external electrical field, which involves changes of dielectric losses and impedance, depending on frequency and temperature. Dielectric properties were measured in the frequency range 20 Hz - 1 MHz. Values for permittivity (εr ranged between 140 - 430. Order of magnitude for electrical resistivity was about 106 Ωm, for impedance 104 - 108 Ω, and loss tangent had values about and greater than 0.05. Current flow through active dielectric takes place through dielectric barrier and throughout conduction bands of thin aluminum and magnesium metal films. Permittivity has nonlinear distribution and complex functional dependences because of significant nonhomogeneity of active microalloyed ceramics. Lower values of electrical resistivity are the result of complex electron and ion transfer of charge through solid phase and pores, with decreased potential barriers height, due to the influence of additives, ingredients and defects. [Projekat Ministarstva nauke Republike Srbije, br. III 45012 i br. ON 172057

  8. Structural and dielectric properties of Cr-doped Ni-Zn nanoferrites

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, S; Anis-ur-Rehman, M; Malik, Muhammad Ali, E-mail: marehman@comsats.edu.pk [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000 (Pakistan)

    2011-02-15

    Cr-doped Ni-Zn ferrite nanoparticles having the general formula Ni{sub 0.5}Zn{sub 0.5}Cr{sub x}Fe{sub 2-x}O{sub 4} (x=0.1, 0.3, 0.5) were prepared by the simplified sol-gel method. The structural and dielectric properties of the samples sintered at 750{+-}5 deg. C were studied. X-ray diffraction (XRD) patterns confirm the single-phase spinel structure of the prepared samples. The crystallite size calculated from the most intense peak (3 1 1) using the Debye-Scherrer formula was 29-34 nm. Scanning electron microscope images showed that the particle size of the samples lies in the nanometer regime. The dielectric constant ({epsilon}{sub r}), dielectric loss tangent (tan {delta}) and ac electrical conductivity ({sigma}{sub ac}) of nanocrystalline Cr-Ni-Zn ferrites were investigated as a function of frequency and Cr concentration. The dependence of {epsilon}{sub r}, tan {delta} and {sigma}{sub ac} on the frequency of alternating applied electric field is in accordance with the Maxwell-Wagner model. The effect of Cr doping on the dielectric and electric properties was explained on the basis of cations distribution in the crystal structure.

  9. Morphological, Raman, electrical and dielectric properties of rare earth doped X-type hexagonal ferrites

    Energy Technology Data Exchange (ETDEWEB)

    Majeed, Abdul, E-mail: abdulmajeed2276@gmail.com [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Center for Computational Materials Science, Department of Physics, University of Malakand, Chakdara, Dir (Lower) 18800 (Pakistan); Khan, Muhammad Azhar, E-mail: azhar.khan@iub.edu.pk [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Raheem, Faseeh ur [Department of Physics, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan); Ahmad, Iftikhar [Center for Computational Materials Science, Department of Physics, University of Malakand, Chakdara, Dir (Lower) 18800 (Pakistan); Department of Physics, Abbottabad University of Science & Technology, Abbottabad (Pakistan); Akhtar, Majid Niaz [Department of Physics, COMSATS Institute of Information Technology, Lahore 54000 (Pakistan); Warsi, Muhammad Farooq [Department of Chemistry, The Islamia University of Bahawalpur, Bahawalpur 63100 (Pakistan)

    2016-12-15

    The influence of rare-earth metals (La, Nd, Gd, Tb, Dy) on morphology, Raman, electrical and dielectric properties of Ba{sub 2}NiCoRE{sub x}Fe{sub 28−}xO{sub 46} ferrites were studied. The scanning electron microscopy (SEM) exhibited the platelet like structure of these hexagonal ferrites. The surface morphology indicated the formation of ferrite grains in the nano-regime scale. The bands obtained at lower wave number may be attributed to the metal-oxygen vibration at octahedral site which confirm the development of hexagonal phase of these ferrites. The resonance peaks were observed in dielectric constant, dielectric loss factor and quality factor versus frequency graphs. These dielectric parameters indicate that these ferrites nano-materials are potential candidates in the high frequency applications. The enhancement in DC electric resistivity from 2.48×10{sup 8} to 1.20×10{sup 9} Ω cm indicates that the prepared materials are beneficial for decreasing the eddy current losses at high frequencies and for the fabrication of multilayer chip inductor (MLCI) devices.

  10. Morphological, Raman, electrical and dielectric properties of rare earth doped X-type hexagonal ferrites

    Science.gov (United States)

    Majeed, Abdul; Khan, Muhammad Azhar; ur Raheem, Faseeh; Ahmad, Iftikhar; Akhtar, Majid Niaz; Warsi, Muhammad Farooq

    2016-12-01

    The influence of rare-earth metals (La, Nd, Gd, Tb, Dy) on morphology, Raman, electrical and dielectric properties of Ba2NiCoRExFe28-xO46 ferrites were studied. The scanning electron microscopy (SEM) exhibited the platelet like structure of these hexagonal ferrites. The surface morphology indicated the formation of ferrite grains in the nano-regime scale. The bands obtained at lower wave number may be attributed to the metal-oxygen vibration at octahedral site which confirm the development of hexagonal phase of these ferrites. The resonance peaks were observed in dielectric constant, dielectric loss factor and quality factor versus frequency graphs. These dielectric parameters indicate that these ferrites nano-materials are potential candidates in the high frequency applications. The enhancement in DC electric resistivity from 2.48×108 to 1.20×109 Ω cm indicates that the prepared materials are beneficial for decreasing the eddy current losses at high frequencies and for the fabrication of multilayer chip inductor (MLCI) devices.

  11. Dielectric properties of doped titanates of transition metals in the millimeter-wavelength range

    Science.gov (United States)

    Rinkevich, A. B.; Perov, D. V.; Kuznetsov, E. A.; Pakhomov, Ya. A.; Ryabkov, Yu. I.

    2016-06-01

    Dielectric properties of ceramic titanates of nickel, cobalt, and manganese and their isomorphically substituted solid solutions are studied. Iron and magnesium are used as dopants. Original methods for solid-state synthesis of titanates allow variations in the dispersity of products. The structure and phase composition of products are analyzed. Microwave measurements of permittivity are performed in a frequency interval of 12-38 GHz. Real and imaginary parts of the permittivities of titanates are determined.

  12. Dielectric properties of neodymium-modified PLZT ceramics

    Science.gov (United States)

    Płońska, M.; Adamczyk, M.

    2015-08-01

    Relaxor ferroelectrics or relaxors are a class of disordered single crystals and ceramic materials, of peculiar structure as well as properties. The commonly known examples of such materials are Pb(Mg,Nb)O3 (PMN) ceramics as well as single crystals. The second most extensively studied relaxor ceramics is lanthanum-doped lead zirconate-titanate, described as x/65/35 PLZT when lanthanum content is x = 6-10 at%. Throughout the last few decades, there has been an increasing interest in rare-earth-doped PLZT ceramics, because PLZT can be easily substituted with lanthanide elements for La3+ ions. For this reason, the present studies concern the changes in microstructure and crystal structure as well as in dielectric properties, caused by modification of 8/65/35 PLZT with neodymium dopant. Modification of this material with Nd3+ influences the microstructure, electrooptical and dielectric properties, whereas the changes in crystal structure are slight. It was also observed that the maximum value of dielectric properties decreases and moves to a low temperature. Described changes in physical properties are associated with the significant improvement of relaxor properties, characteristic for pure 8/65/35 PLZT ceramics.

  13. Dielectric properties of wheat flour mixed with oat meal

    Science.gov (United States)

    Łuczycka, D.; Czubaszek, A.; Fujarczuk, M.; Pruski, K.

    2013-03-01

    Possibilities of using electric methods for determining admixtures of oat meal to wheat flour, type 650 are presented. In wheat flour, oat meal and mixtures containing 10, 20 and 30% of the oat meal, moisture, protein, starch and ash content, sedimentation value, yield and softening of wet gluten were determined. In samples containing 0, 5, 10, 15, 20, 25, 30 and 100% of oat meal, the dielectric loss factor and conductivity were determined using an impedance analyzer for electromagnetic field frequency ranging from 0.1-20 kHz. It was found that the dielectric loss factor varied for tested material. The best distinguishing between tested mixtures was obtained at the measuring electromagnetic field frequency of 20 kHz. The loss factor was significantly correlated with the yield of wet gluten and the sedimentation value, parameters indicating the amount and quality of gluten proteins in flour.

  14. Dielectric and structural properties of ferroelectric betaine arsenate films

    Science.gov (United States)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Yurko, E. I.; Svinarev, F. B.

    2014-12-01

    Ferroelectric films of betaine arsenate and partially deuterated betaine arsenate have been grown by evaporation on LiNbO3, α-Al2O3, and NdGaO3 substrates with a preliminarily deposited structure of interdigitated electrodes, as well as on the Al/glass substrate. This paper presents the results of the examination of the block structure of the films in a polarizing microscope, the X-ray diffraction analysis of their crystal structure, and the investigation of the dielectric properties in a measuring field oriented both parallel and perpendicular to the plane of the film. The transition of the films to the ferroelectric state at T = T c is accompanied by anomalies of the capacitance of the structure, an increase in the dielectric loss, and the appearance of dielectric hysteresis loops. The growth of the films from a solution of betaine arsenate in a heavy water leads to an increase in the ferroelectric transition temperature from T c = 119 K in the films without deuterium to T c = 149 K, which corresponds to the degree of deuteration of approximately 60-70%. The dielectric and structural properties of the films are compared with those of the betaine arsenate single crystals and the previously studied films of betaine phosphite and glycine phosphite.

  15. Electrical properties and dielectric spectroscopy of Ar{sup +} implanted polycarbonate

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, Mahak, E-mail: mahak.chawla@gmail.com; Shekhawat, Nidhi; Aggarwal, Sanjeev; Sharma, Annu [Department of Physics, Kurukshetra University, Kurukshetra - 136119 (India); Nair, K. G. M. [Consultant, UGC-DAE Consortium for Scientific Research, Kalpakkam Node, Kokilamedu-603104, Tamilnadu (India)

    2015-05-15

    The aim of the present paper is to study the effect of argon ion implantation on electrical and dielectric properties of polycarbonate. Specimens were implanted with 130 keV Ar{sup +} ions in the fluence ranging from 1×10{sup 14} to 1×10{sup 16} ions cm{sup −2}. The beam current used was ∼0.40 µA cm{sup −2}. The electrical conduction behaviour of virgin and Ar{sup +} implanted polycarbonate specimens have been studied through current-voltage (I-V characteristic) measurements. It has been observed that after implantation conductivity increases with increasing ion fluence. The dielectric spectroscopy of these specimens has been done in the frequency range of 100 kHz-100 MHz. Relaxation processes were studied by Cole-Cole plot of complex permittivity (real part of complex permittivity, ε′ vs. imaginary part of complex permittivity, ε″). The Cole-Cole plots have also been used to determine static dielectric constant (ε{sub s}), optical dielectric constant (ε{sub ∞}), spreading factor (α), average relaxation time (τ{sub 0}) and molecular relaxation time (τ). The dielectric behaviour has been found to be significantly affected due to Ar{sup +} implantation. The possible correlation between this behaviour and the changes induced by the implantation has been discussed.

  16. Dielectric properties of Ga{sub 2}O{sub 3}-doped barium iron niobate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Sanjoom, Kachaporn [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand); Pengpat, Kamonpan; Eitssayeam, Sukum; Tunkasiri, Tawee [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Rujijanagul, Gobwute [Department of Physics and Materials Science, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Materials Science Research Center, Faculty of Science, Chiang Mai University, Chiang Mai, 50200 (Thailand); Thailand Center of Excellence in Physics, Commission on Higher Education, 328 Sri Ayutthaya Road, Bangkok, 10400 (Thailand)

    2014-08-15

    Ga-doped BaFe{sub 0.5}Nb{sub 0.5}O{sub 3} (Ba(Fe{sub 1-x}Ga{sub x}){sub 0.5}Nb{sub 0.5}O{sub 3}) ceramics were fabricated and their properties were investigated. All ceramics showed perovskite structure with cubic symmetry and the solubility of Ga in BFN ceramics had a limit at x = 0.2. Examination of the dielectric spectra indicated that all ceramic samples presented high dielectric constants that were frequency dependent. The x = 0.2 ceramic showed a very high dielectric constant (ε{sub r} > 240 000 at 1 kHz) while the x = 0.4 sample exhibited high thermal stability of dielectric constant with low loss tangent from room temperature (RT) to 100 C with ε{sub r} > 28 000 (at 1 kHz) when compared to other samples. By using a complex impedance analysis technique, bulk grain, grain boundary, and electrode response were found to affect the dielectric behavior that could be related to the Maxwell-Wagner polarization mechanism. (copyright 2014 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Structures, Phase Transformations, and Dielectric Properties of BiTaO4 Ceramics.

    Science.gov (United States)

    Zhou, Di; Fan, Xiao-Qin; Jin, Xiao-Wei; He, Duan-Wei; Chen, Guo-Hua

    2016-11-21

    Low (α)- and high-temperature (β) forms of BiTaO4 have attracted much attention due to their dielectric and photocatalytic properties. In the present work, a third form, the so-called HP-BiTaO4, was synthesized at high temperature and pressure. The phase evolution, phase transformations, and dielectric properties of α- and β-BiTaO4 and HP-BiTaO4 ceramics are studied in detail. β-BiTaO4 ceramics densified at 1300 °C with the microwave permittivity εr ≈ 53, the microwave quality factor Qf ≈ 12070 GHz, and the temperature coefficient of resonant frequency τf ≈ -200 ppm/°C. HP-BiTaO4 ceramics were synthesized at 5 GPa and 1300 °C followed by annealing at 600 °C. In contrast with the α phase, HP-BiTaO4 exhibited εr ≈ 195 at 1 kHz to 10 MHz, accompanied by a low dielectric loss of ∼0.004. The relation between structure and dielectric properties is discussed in the context of Shannon's additive rule and bond theory.

  18. Low frequency ac conduction and dielectric relaxation in poly(N-methyl pyrrole)

    Indian Academy of Sciences (India)

    Amarjeet K Narula; Ramadhar Singh; Subhas Chandra

    2000-06-01

    The ac conductivity and dielectric constant of poly(N-methyl pyrrole) thin films have been investigated in the temperature range 77–350 K and in the frequency range 102–106 Hz. The well defined loss peaks have been observed in the temperature region where measured ac conductivity approaches dc conductivity. These loss peaks are associated with the hopping of the charge carriers. The frequency and temperature dependence of ac conductivity have been qualitatively explained by considering the contribution from two mechanisms; one giving a linear dependence of conductivity on frequency and other having distribution of relaxation times giving rise to broad dielectric loss peak.

  19. Temperature-dependent dielectric properties of slightly hydrated horn keratin.

    Science.gov (United States)

    Rizvi, Tasneem Zahra; Khan, Muhammad Abdullah

    2008-04-01

    With an aim to reveal the mechanism of protein-water interaction in a predominantly two phase model protein system this study investigates the frequency and temperature dependence of dielectric constant epsilon' and loss factor epsilon'' in cow horn keratin in the frequency range 30 Hz to 3 MHz and temperature range 30-200 degrees C at two levels of hydration. These two levels of hydration were achieved by exposing the sample to air at 50% relative humidity (RH) at ambient temperature and by evacuating the sample for 72 h at 105 degrees C. A low frequency dispersion (LFD) and an intermediate frequency alpha-dispersion were the two main dielectric responses observed in the air-dried sample. The LFD and the high frequency arm of the alpha-dispersion followed the same fractional power law of frequency. Within the framework of percolation cluster model these dispersions, respectively have been attributed to percolation of protons between and within the clusters of hydrogen-bonded water molecules bound to polar or ionizable protein components. The alpha-dispersion peak, which results from intra-cluster charge percolation conformed to Cole-Cole modified Debye equation. Temperature dependence of the dielectric constant in the air-dried sample exhibited peaks at 120 and 155 degrees C which have been identified as temperatures of onset of release of water bound to polar protein components in the amorphous and crystalline regions, respectively. An overall rise in the permittivity was observed above 175 degrees C, which has been identified as the onset of chain melting in the crystalline region of the protein.

  20. Effects of Substrates with Different Dielectric Parameters on Left-Handed Frequency of Left-Handed Materials

    Institute of Scientific and Technical Information of China (English)

    QUAN Bao-Gang; LI Chao; SUI Qiang; LI Jun-Jie; LIU Wu-Ming; LI Fang; GU Chang-Zhi

    2005-01-01

    @@ Wedge-shaped left-handed materials (LHMs) with split ring resonators and wires structures are fabricated by photolithography and lift-off techniques, and the variation of left-handed frequency induced by substrates with different dielectric parameters is investigated. The Snell refraction experiments of the LHM samples are carried out on an angular resoled microwave spectrometer, and the results indicate that the left-handed frequencies of the LHMs shifted downward from 10.57 GHz to 9.74 GHz when the dielectric parameters of the LHM substrates increase from 3.7 to 4.8. Moreover, the finite difference time domain method is used to simulate the microwave transmission properties of the left-handed materials with different substrates, and the experimental results are in agreement with the numerical simulation results. In addition, the reason for the shifting of the left-handedfrequency of the LHMs is discussed theoretically.

  1. Radio frequency and capacitive sensors for dielectric characterization of low-conductivity media

    Science.gov (United States)

    Sheldon, Robert T.

    Low-conductivity media are found in a vast number of applications, for example as electrical insulation or as the matrix polymer in high strength-to-weight ratio structural composites. In some applications, these materials are subjected to extreme environmental, thermal, and mechanical conditions that can affect the material's desired performance. In a more general sense, a medium may be comprised of one or more layers with unknown material properties that may affect the desired performance of the entire structure. It is often, therefore, of great import to be able to characterize the material properties of these media for the purpose of estimating their future performance in a certain application. Low-conductivity media, or dielectrics, are poor electrical conductors and permit electromagnetic waves and static electric fields to pass through with minimal attenuation. The amount of electrical energy that may be stored (and lost) in these fields depends directly upon the material property, permittivity, which is generally complex, frequency-dependent and has a measurable effect on sensors designed to characterize dielectric media. In this work, two different types of dielectric sensors: radio frequency resonant antennas and lower-frequency (field of nondestructive evaluation as well. Each configuration of a patch antenna has a single lowest resonant (dominant mode) frequency that is dependent upon the antenna's substrate material and geometry as well as the permittivity and geometry of exterior materials. Here, an extant forward model is validated using well-characterized microwave samples and a new method of resonant frequency and quality factor determination from measured data is presented. Excellent agreement between calculated and measured values of sensor resonant frequency was obtained for the samples studied. Agreement between calculated and measured quality factor was good in some cases but incurred the particular challenge of accurately quantifying multiple

  2. AFM based dielectric spectroscopy: extended frequency range through excitation of cantilever higher eigenmodes.

    Science.gov (United States)

    Miccio, Luis A; Kummali, Mohammed M; Schwartz, Gustavo A; Alegría, Ángel; Colmenero, Juan

    2014-11-01

    In the last years, a new AFM based dielectric spectroscopy approach has been developed for measuring the dielectric relaxation of materials at the nanoscale, the so called nanoDielectric Spectroscopy (nDS). In spite of the effort done so far, some experimental aspects of this technique remain still unclear. In particular, one of these aspects is the possibility of extending the experimental frequency range, to date limited at high frequencies by the resonance frequency of the AFM cantilever as a main factor. In order to overcome this limitation, the electrical excitation of cantilever higher eigenmodes for measuring the dielectric relaxation is here explored. Thus, in this work we present a detailed experimental analysis of the electrical excitation of the cantilever second eigenmode. Based on this analysis we show that the experimental frequency range of the AFM based dielectric spectroscopy can be extended by nearly two decades with a good signal-to-noise ratio. By using the combination of first and second cantilever eigenmodes we study dissipation processes on well known PVAc based polymeric samples. Both, relaxation spectra and images with molecular dynamics contrast were thus obtained over this broader frequency range.

  3. Influence of Ni{sup 2+} substitution on the structural, dielectric and magnetic properties of Cu–Cd ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hashim, Mohd., E-mail: md.hashim09@gmail.com [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Alimuddin [Department of Applied Physics, Aligarh Muslim University, Aligarh 202 002 (India); Shirsath, Sagar E. [Spin Device Technology Centre, Department of Information Engineering, Shinshu University, Nagano 380-8553 (Japan); Kotnala, R.K. [National Physical Laboratory (CSIR), Dr. K.S. Krishnan Road, New Delhi 110 012 (India); Meena, Sher Singh [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kumar, Shalendra [Department of Physics, Pohang University of Science and Technology, Pohang 790 784 (Korea, Republic of); Roy, Aashis [Department of Materials Science, Gulbarga University, Gulbarga 585106, Karnataka (India); Jotania, R.B. [Department of Physics, University School of Sciences, Gujarat University, Ahmedabad 380 009 (India); Bhatt, Pramod [Solid State Physics Division, Bhabha Atomic Research Centre, Mumbai 400 085 (India); Kumar, Ravi [Centre for Material Science Engineering, National Institute of Technology, Hamirpur, HP 171 005 (India)

    2013-10-05

    Highlights: •XRD and IR measurements reveal the formation of Cu–Cd–FeO in spinel phase. •The dielectric response shows decreasing trend while resistivity increases with enhancing the doping ion content. •Temperature dependent magnetization study shows that the magnetization and Curie temperature increases with increase in Ni{sup 2+} substitution. -- Abstract: Nanoparticles with compositions of Cu{sub 0.4−0.5x}Cd{sub 0.2}Ni{sub 0.4+x}Fe{sub 2−0.5x}O{sub 4} (0.0 ⩽ x ⩽ 0.5) were successfully synthesized by a citrate–nitrate sol–gel auto combustion route. The combusted powder was calcinated at four hours in a furnace and then slowly cooled to room temperature. The analysis methods of FTIR, XRD, FESEM, VSM and dielectric measurements were used to characterize prepared magnetic particles. The effect of Ni{sup 2+} substitution on structural, magnetic and dielectric properties of Cu–Cd ferrite nanoparticles was studied. The comprehensive studies on compositional and frequency dependent dielectric properties were carried out by means of AC conductivity (σ{sub ac}), imaginary dielectric constant (ε′′), loss tangent (tan δ), impedance and dielectric modulus (real and imaginary) measurements in frequency range of 50 Hz–5 MHz at room temperature. The structural properties investigated by using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. X-ray diffraction pattern and FTIR results revealed that synthesized samples are in single phase. It is observed that the dielectric constant (ε′′) and dielectric loss (tan δ) value decreases with increase in Ni{sup 2+} concentration (x). At low frequency the Maxwell type interfacial polarization was observed. Magnetization measurement shows that the Curie temperature of the samples increases with Ni{sup 2+} concentration, which is explained by a change in the A–O–B super exchange interaction.

  4. Studies of ferroelectric and dielectric properties of pure and doped barium titanate prepared by sol-gel method

    Energy Technology Data Exchange (ETDEWEB)

    Bisen, Supriya; Mishra, Ashutosh; Jarabana, Kanaka M. [School of Physics, Vigyan Bhawan, Devi Ahilya University, Khandwa Road Indore-452001 (India)

    2016-05-23

    In this work, Barium Titanate (BaTiO{sub 3}) powders were synthesized via Sol-Gel auto combustion method using citric acid as a chelating agent. We study the behavior of ferroelectric and dielectric properties of pure and doped BaTiO{sub 3} on different concentration. To understand the phase and structure of the powder calcined at 900°C were characterized by X-ray Diffraction shows that tetragonal phase is dominant for pure and doped BTO and data fitted by Rietveld Refinement. Electric and Dielectric properties were characterized by P-E Hysteresis and Dielectric measurement. In P-E measurement ferroelectric loop tracer applied for different voltage. The temperature dependant dielectric constant behavior was observed as a function of frequency recorded on hp-Hewlett Packard 4192A, LF impedance, 5Hz-13Hz analyzer.

  5. Effect of substrate temperature on microstructures and dielectric properties of compositionally graded BST thin films

    Institute of Scientific and Technical Information of China (English)

    ZHANG Bai-shun; GUO Tao; ZHANG Tian-jin; WANG Jin-zhao; QUAN Zu-ci

    2006-01-01

    Compositionally graded Ba1-xSrxTiO3 (BST) (x = 0-0.3) thin films were prepared on Pt/Ti/SiO2/Si substrate at different substrate temperatures ranging from 550 ℃ to 650 ℃ by radio-frequency (rf) magnetron sputtering. The effect of substrate temperature on the preferential orientation,microstructures and dielectric properties of compositionally graded BST thin films was investigated by X-ray diffraction,scanning electron microscopy and dielectric frequency spectra,respectively. As the temperature increases,the preferential orientation evolves in the order: randomly orientation→ (111) → highly oriented (111) (α(111) = 60.2%). The surface roughness of the graded BST thin films varies with the substrate temperatures. No visible internal interface in the compositionally graded thin films can be observed in the cross-sectional SEM images. The graded BST thin films deposited at 650 ℃ possess the highest dielectric constant and dielectric loss,which are 408 and 0.013,respectively.

  6. Microwave Dielectric Properties of Alfalfa Leaves From 0.3 to 18 GHz

    Energy Technology Data Exchange (ETDEWEB)

    Sokhansanj, Shahabaddine [ORNL; Shrestha, Bijay [University of Saskatchewan; Wood, H.C. [University of Saskatchewan

    2011-01-01

    Dielectric properties (i.e., permittivity) are essential in designing, simulating, and modeling microwave applications. The permittivity of stacked leaves of alfalfa (Medicago sativa) were measured with a network analyzer and a coaxial probe, and the effect of moisture content (MC: 12% 73% wet basis), frequency (300 MHz to 18 GHz), bound water (Cole Cole dispersion equation), temperature ( 15 C and 30 C), leaf-orientation, and pressure (0 11 kPa) were investigated. The measured permittivity increased with MC. A critical moisture level (CML) of 23% was reported, below which the permittivity decreased with increasing frequency at 22 C. Above CML and up to 5 GHz, the dielectric constants followed the Cole Cole dispersion, and the dielectric loss factors consisted of ionic and bound water losses. Above 5 GHz, the behavior of the dielectric constant was similar to that of free water, and the polar losses became dominant. Above 0 C, the measured permittivity followed a trend similar to that of free saline water and was characterized by the Debye equation. Below 0 C, it was dominated by nonfreezing bound and unfrozen supercooled moistures. The relaxation parameters and the optimum pressure (9 kPa) for the leaf measurements were determined. The effects of variations among the samples, and their orientations had negligible effects on the measured permittivity.

  7. Study on Microwave Dielectric Property of Carbon Black and Short Carbon Fibers

    Institute of Scientific and Technical Information of China (English)

    WU Hong-huan; ZHU Dong-mei; LUO Fa; ZHOU Wan-cheng; WANG Xiao-yan

    2006-01-01

    Carbon black and carbon fibers of different lengths were introduced in different matrices at different ratios to explore their microwave dielectric properties under 8.2 GHz-12.4 GHz. It is found that the actual dielectric constants of the samples containing carbon black are in a two-order function of the contents of carbon black ((з)′,(з)″=Av2+Bv+C) and the complex dielectric constants show an obvious frequency response. Of the added fibers of different lengths, the 4 mm-long one could well disperse in the matrices having not only good frequency response, but also larger real parts, imaginary parts and loss values. The imaginary parts and the loss values (tanδ) of the samples with 4 mm-long carbon fibers added increase linearly with the contents of fiber increasing. So it is practicable to adjust the dielectric parameters of the material in a wide range by changing the added amount of carbon black, and the carbon fiber or altering the lengths of the carbon fiber added.

  8. Dielectric properties of low-water-content tissues.

    Science.gov (United States)

    Smith, S R; Foster, K R

    1985-09-01

    The dielectric properties of two low-water-content tissues, bone marrow and adipose tissue, were measured from 1 kHz to 1 GHz. From 1 kHz to 13 MHz, the measurements were performed using a parallel-plate capacitor method. From 10 MHz to 1 GHz, a reflection coefficient technique using an open-ended coaxial transmission line was employed. The tissue water contents ranged from 1 to almost 70% by weight. The dielectric properties correlate well with the values predicted by mixture theory. Comparison with previous results from high-water-content tissues suggests that bone marrow and adipose tissues contain less motionally altered water per unit dry volume than do the previously studied tissues with lower lipid fractions. The high degree of structural heterogeneity of these tissues was reflected in the large scatter of the data, a source of uncertainty that should be considered in practical applications of the present data.

  9. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin;

    of electrical breakdown and achievable strain.[2]In this work, three liquid additives - inert silicone oil, chloropropyl-functional silicone oil, and synthesized chloropropyl-functional copolymer - were blended into commercial silicone elastomers, and their properties were investigated.The functional groups......Dielectric elastomers (DEs) change their shape and size under a high voltage or reversibly generate a high voltage when deformed. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young......’s modulus and increasing the dielectric permittivity of silicone elastomers. One such prominent method of modifying the properties is by adding suitable additives.[1] The major drawbacks for adding solid fillers are agglomeration and increasing stiffness which is often accompanied by the decrease...

  10. Silicone elastomers with superior softness and dielectric properties

    DEFF Research Database (Denmark)

    Yu, Liyun; Madsen, Frederikke Bahrt; Zakaria, Shamsul Bin;

    of electrical breakdown and achievable strain.[2] In this work, three liquid additives - inert silicone oil, chloropropyl-functional silicone oil, and synthesized chloropropyl-functional copolymer - were blended into commercial silicone elastomers, and their properties were investigated.The functional groups......Dielectric elastomers (DEs) change their shape and size under a high voltage or reversibly generate a high voltage when deformed. The obstacle of high driving voltages, however, limits the commercial viability of the technology at present. Driving voltage can be lowered by decreasing the Young......’s modulus and increasing the dielectric permittivity of silicone elastomers. One such prominent method of modifying the properties is by adding suitable additives. [1] The major drawbacks for adding solid fillers are agglomeration and increasing stiffness which is often accompanied by the decrease...

  11. SHI induced modification in structural, optical, dielectric and thermal properties of poly ethylene oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Patel, Gnansagar B.; Bhavsar, Shilpa [Department of Physics, The M.S. University of Baroda, Vadodara 390002 (India); Singh, N.L., E-mail: nl.singh-phy@msubaroda.ac.in [Department of Physics, The M.S. University of Baroda, Vadodara 390002 (India); Singh, F.; Kulriya, P.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2016-07-15

    Poly ethylene oxide (PEO) films were synthesized by solution cast method. These self-standing films were exposed with 60 MeV C{sup +5} ion and 100 MeV Ni{sup +7} ion at different fluences. SHI induced effect was investigated by employing various techniques. The crystalline size decreased upon irradiation as observed from XRD analysis. FTIR analysis reveals the decrement in the peak intensity upon irradiation. Tauc’s method was used to determine the optical band gap (E{sub g}), which shows decreasing trends with increase of fluence. The dielectric properties were investigated in the frequency range 10 Hz to 10 MHz for unirradiated and irradiated films. The dielectric constant remains same for the broad-spectrum of frequency and increases at lower frequency. The dielectric loss also moderately influence as a function of frequency due to irradiation. DSC analysis validated the results of XRD. Scanning electron microscopy (SEM) reveals that there is significant change in the surface morphology due to irradiation.

  12. Dielectric Properties and Characterisation of Titanium Dioxide Obtained by Different Chemistry Methods

    Directory of Open Access Journals (Sweden)

    Aleksandra Wypych

    2014-01-01

    Full Text Available We made comparison of titanium dioxide powders obtained from three syntheses including sol-gel and precipitation methods as well as using layered (tetramethylammonium titanate as a source of TiO2. The obtained precursors were subjected to step annealing at elevated temperatures to transform into rutile form. The transformation was determined by Raman measurements in each case. The resulting products were characterised using Raman spectroscopy and dynamic light scattering. The main goal of the studies performed was to compare the temperature of the transformation in three titania precursors obtained by different methods of soft chemistry routes and to evaluate dielectric properties of rutile products by means of broadband dielectric spectroscopy. Different factors affecting the electrical properties of calcinated products were discussed. It was found that sol-gel synthesis provided rutile form after annealing at 850°C with the smallest particles size about 20 nm, the highest value of dielectric permittivity equal to 63.7, and loss tangent equal to 0.051 at MHz frequencies. The other powders transformed to rutile at higher temperature, that is, 900°C, exhibit lower value of dielectric permittivity and had a higher value of particles size. The correlation between the anatase-rutile transformation temperature and the size of annealed particles was proposed.

  13. Changes in the dielectric properties of medaka fish embryos during development, studied by electrorotation

    Energy Technology Data Exchange (ETDEWEB)

    Shirakashi, Ryo, E-mail: aa21150@iis.u-tokyo.ac.jp [Institute of Industrial Science, The University of Tokyo, Tokyo 153-8505 (Japan); Mischke, Miriam [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fischer, Peter [Physiologische Chemie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Memmel, Simon [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Krohne, Georg [Abteilung fuer Elektronenmikroskopie, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany); Fuhr, Guenter R. [Lehrstuhl fuer Biotechnologie und Medizintechnik, Universitaet des Saarlandes, Saarbruecken (Germany); Zimmermann, Heiko [Lehrstuhl fuer Molekulare und Zellulaere Biotechnologie, Universitaet des Saarlandes, Saarbruecken (Germany); Sukhorukov, Vladimir L., E-mail: sukhorukov@biozentrum.uni-wuerzburg.de [Lehrstuhl fuer Biotechnologie und Biophysik, Biozentrum, Universitaet Wuerzburg, Wuerzburg (Germany)

    2012-11-09

    Highlights: Black-Right-Pointing-Pointer Electrorotation offers a non-invasive tool for dielectric analysis of fish embryos. Black-Right-Pointing-Pointer The three-shell dielectric model matches the rotation spectra of medaka eggs. Black-Right-Pointing-Pointer The capacitance value suggests a double-membrane structure of yolk envelope. -- Abstract: The Japanese medaka fish, Oryzias latipes, has become a powerful vertebrate model organism in developmental biology and genetics. The present study explores the dielectric properties of medaka embryos during pre-hatching development by means of the electrorotation (ROT) technique. Due to their layered structure, medaka eggs exhibited up to three ROT peaks in the kHz-MHz frequency range. During development from blastula to early somite stage, ROT spectra varied only slightly. But as the embryo progressed to the late-somite stage, the ROT peaks underwent significant changes in frequency and amplitude. Using morphological data obtained by light and electron microscopy, we analyzed the ROT spectra with a three-shell dielectric model that accounted for the major embryonic compartments. The analysis yielded a very high value for the ionic conductivity of the egg shell (chorion), which was confirmed by independent osmotic experiments. A relatively low capacitance of the yolk envelope was consistent with its double-membrane structure revealed by transmission electron microscopy. Yolk-free dead eggs exhibited only one co-field ROT peak, shifted markedly to lower frequencies with respect to the corresponding peak of live embryos. The dielectric data may be useful for monitoring the development and changes in fish embryos' viability/conditions in basic research and industrial aquaculture.

  14. The 'emergent scaling' phenomenon and the dielectric properties of random resistor-capacitor networks

    Energy Technology Data Exchange (ETDEWEB)

    Bouamrane, R [LEPM, Departement de Physique, USTO-MB, BP 1505 El M' Naouer, Oran 31000 (Algeria); Almond, D P [Department of Engineering and Applied Science, University of Bath, Bath BA2 7AY (United Kingdom)

    2003-06-25

    An efficient algorithm, based on the Frank-Lobb reduction scheme, for calculating the equivalent dielectric properties of very large random resistor-capacitor (R-C) networks has been developed. It has been used to investigate the network size and composition dependence of dielectric properties and their statistical variability. The dielectric properties of 256 samples of random networks containing: 512, 2048, 8192 and 32 768 components distributed randomly in the ratios 60% R-40% C, 50% R-50% C and 40% R-60% C have been computed. It has been found that these properties exhibit the anomalous power law dependences on frequency known as the 'universal dielectric response' (UDR). Attention is drawn to the contrast between frequency ranges across which percolation determines dielectric response, where considerable variability is found amongst the samples, and those across which power laws define response where very little variability is found between samples. It is concluded that the power law UDRs are emergent properties of large random R-C networks.

  15. Study of Some Dielectric Properties of Suspensions of Magnesium Particles in Mineral Oil

    Science.gov (United States)

    Altshuller, Aubrey P

    1954-01-01

    The variation of dielectric constant has been measured as a function of the concentration of magnesium particles; the shape, size, and degree of oxidation of the particles; the temperature; and the frequency of oscillation. The variation of dielectric constant and settling rate was investigated as a function of time. Also investigated were the effects of particle concentration, shape and time on dielectric losses.

  16. Simultaneous and accurate measurement of the dielectric constant at many frequencies spanning a wide range

    CERN Document Server

    Pérez-Aparicio, Roberto; Cottinet, Denis; Tanase, Marius; Metz, Pascal; Bellon, Ludovic; Naert, Antoine; Ciliberto, Sergio

    2015-01-01

    We present an innovative technique which allows the simultaneous measurement of the dielectric constant of a material at many frequencies, spanning a four orders of magnitude range chosen between 10 --2 Hz and 10 4 Hz. The sensitivity and accuracy are comparable to those obtained using standard single frequency techniques. The technique is based on three new and simple features: a) the precise real time correction of the amplication of a current amplier; b) the specic shape of the excitation signal and its frequency spectrum; and c) the precise synchronization between the generation of the excitation signal and the acquisition of the dielectric response signal. This technique is useful in the case of relatively fast dynamical measurements when the knowledge of the time evolution of the dielectric constant is needed.

  17. Synthesis and dielectric properties of zinc oxide nanoparticles using a biotemplate

    Energy Technology Data Exchange (ETDEWEB)

    P, Sharmila P, E-mail: sharmilavishram@gmail.com [Sree Narayana College, Kollam, Kerala, India and T.K Madhva Memorial College, Nangiarkulungara, Alapuzha, Kerala (India); Tharayil, Nisha J., E-mail: nishajohntharayil@gmail.com [Sree Narayana College for Women Kollam, Kerala (India)

    2014-10-15

    Zinc Oxide nanoparticles are synthesized using DNA as capping agent. Zinc oxide nanoparticles are synthesized using DNA as a capping agent. Structural and morphological characterizations are done using SEM, FTIR and XRD. The particle size and lattice parameters are calculated from the diffraction data. The optical properties are studied using UV-Vis absorption spectroscopy and bandgap variation with temperature is determined. The dielectric property of nanoparticles is studied by varying temperature and frequency. The dielectric constant and dispersion parameters are found out. Method of Cole-Cole analysis is used to study the high temperature dispersion of relaxation time. The variation of both AC and DC conductivity are studied and activation energy calculated.

  18. Microstructural, Optical and Dielectric Properties of Al-Incorporated SnO2 Nanoparticles

    Science.gov (United States)

    Ahmed, Ateeq; Tripathi, P.; Naseem Siddique, M.; Ali, Tinku

    2017-08-01

    In this work, Pure SnO2 and Al doped SnO2 nanoparticles with the composition Sn1-xAlxO2 (x = 0, and 0.05) have been successfully prepared using sol-gel technique. The effect of Al dopant on microstructural, optical and dielectric properties has been investigated by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Ultraviolet (UV-Visible) absorption spectroscopy andImpedance spectroscopy (LCR meter)respectively. The XRD patterns indicated tetragonal rutile structure with single phase without any detectable impurity for all samples and incorporation of Al ions into the SnO2 lattice. Crystalline size decreased with aluminum content. The results of SEM confirm nanoparticles size decreases with Al dopant. UV-Visible results showed that optical band also decreases when Al is doped into pure SnO2 lattice. Frequency dependent dielectric properties of pure and doped SnO2 nanoparticles have been also studied.

  19. Room temperature optical and dielectric properties of Sr and Ni doped lanthanum ferrite nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Naseem, Swaleha; Khan, Wasi, E-mail: wasiamu@gmail.com; Singh, B. R.; Naqvi, A. H. [Centre of Excellence in Materials Science (Nanomaterials), Department of Applied Physics, Z.H. College of Engg. & Technology, Aligarh Muslim University, Aligarh 202002 (India)

    2015-06-24

    Strontium and nickel doped lanthanum ferrite (LaFeO{sub 3}) nanoparticles (NPs) were prepared reverse micelle (RM) and calcinated at 700°C. Microstructural studies were carried by XRD and SEM/EDS techniques. The results of structural characterization show the formation of all samples in single phase without any impurity. Optical properties were studied by UV- visible spectroscopy and band gap energy was estimated 3.89 eV. Room temperature dielectric constant (ε’) decreases abruptly at lower frequencies owing to the charge transport relaxation time. The observed behavior of the dielectric properties can be attributed on the basis of Koop’s theory based on Maxwell-Wagner’s two layer model in studied nanoparticles.

  20. Structure-property relationships in polymers for dielectric capacitors

    Science.gov (United States)

    Gupta, Sahil

    Effective energy storage is a key challenge of the 21st century that has fueled research in the area of energy storage devices. In this dissertation, structure-property relationships have been evaluated for polymers that might be suitable for storing energy in high-energy density, high-temperature capacitors. Firstly, hydroxyl-modified polypropylenes (PPOH) were synthesized by copolymerization of the propylene and undecenyloxytrimethylsilane monomers. The presence of H-bonding in PPOH copolymers increased their glass-transition temperature. Steric hindrance by the comonomer reduced the PP crystal growth rate and crystal size, resulting in a melting point depression. The comonomer was restricted outside the crystalline domains leaving the alpha-monoclinic crystal structure of PP unaffected, but increasing the fold-surface free energy. Crystallization was slower for PPOH copolymers than PP, but exhibited a skewed bell curve as a function of hydroxyl concentration. H-bonding persisted even at melt temperatures up to 250°C resulting in a higher elasticity and viscosity for PPOH copolymers. Secondly, sulfonated poly(ether ether ketone) (HSPEEK) was synthesized by sulfonating PEEK with sulfuric acid, and further neutralized with Zn to obtain ZnSPEEK. The thermal and dielectric properties of SPEEK were compared with PEEK. The glass-transition increased and melting point were high enough to enable the use of polymer at 180°C. The incorporation of sulfonic groups in PEEK increased the dielectric constant. HSPEEK had a higher dielectric constant than ZnSPEEK due to higher dipolar mobility, but the dielectric loss was also higher for HSPEEK due to electrode polarization and DC conduction. These results were consistent with our observations from sulfonated polystyrene (HSPS), which was used as a >model&lang' polymer. Lastly, commercial poly(4-methyl-1-pentene) (P4MP) was characterized to check its viability as a high-temperature polymer dielectric. Thermal stability up to

  1. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Science.gov (United States)

    Yang, Yang; Wang, Ziyu; Ding, Yi; Lu, Zhihong; Sun, Haoliang; Li, Ya; Wei, Jianhong; Xiong, Rui; Shi, Jing; Liu, Zhengyou; Lei, Qingquan

    2013-11-01

    This work reports the excellent dielectric properties of polyimide (PI) embedded with CaCu3Ti4O12 (CCTO) nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz-1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67) is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  2. Research Update: Polyimide/CaCu3Ti4O12 nanofiber functional hybrid films with improved dielectric properties

    Directory of Open Access Journals (Sweden)

    Yang Yang

    2013-11-01

    Full Text Available This work reports the excellent dielectric properties of polyimide (PI embedded with CaCu3Ti4O12 (CCTO nanofibers. The dielectric behaviors were investigated over a frequency of 100 Hz–1 MHz. It is shown that embedding CCTO nanofibers with high aspect ratio (67 is an effective means to enhance the dielectric permittivity and reduce the percolation threshold. The dielectric permittivity of PI/CCTO nanofiber composites is 85 with 1.5 vol.% loading of filler, also the dielectric loss is only 0.015 at 100 Hz. Monte Carlo simulation was used to investigate the percolation threshold of CCTO nanofibers reinforced polyimide matrix by using excluded volume theory and soft, hard-core models. The results are in good agreement with the percolation theory and the hard-core model can well explain the percolation phenomena in PI/CCTO nanofiber composites. The dielectric properties of the composites will meet the practical requirements for the application in high dielectric constant capacitors and high energy density materials.

  3. Radio to microwave dielectric characterisation of constitutive electromagnetic soil properties using vector network analyses

    Science.gov (United States)

    Schwing, M.; Wagner, N.; Karlovsek, J.; Chen, Z.; Williams, D. J.; Scheuermann, A.

    2016-04-01

    The knowledge of constitutive broadband electromagnetic (EM) properties of porous media such as soils and rocks is essential in the theoretical and numerical modeling of EM wave propagation in the subsurface. This paper presents an experimental and numerical study on the performance EM measuring instruments for broadband EM wave in the radio-microwave frequency range. 3-D numerical calculations of a specific sensor were carried out using the Ansys HFSS (high frequency structural simulator) to further evaluate the probe performance. In addition, six different sensors of varying design, application purpose, and operational frequency range, were tested on different calibration liquids and a sample of fine-grained soil over a frequency range of 1 MHz-40 GHz using four vector network analysers. The resulting dielectric spectrum of the soil was analysed and interpreted using a 3-term Cole-Cole model under consideration of a direct current conductivity contribution. Comparison of sensor performances on calibration materials and fine-grained soils showed consistency in the measured dielectric spectra at a frequency range from 100 MHz-2 GHz. By combining open-ended coaxial line and coaxial transmission line measurements, the observable frequency window could be extended to a truly broad frequency range of 1 MHz-40 GHz.

  4. Condition assessment of transformer insulation using dielectric frequency response analysis by artificial bee colony algorithm

    Directory of Open Access Journals (Sweden)

    Bigdeli Mehdi

    2016-03-01

    Full Text Available Transformers are one of the most important components of the power system. It is important to maintain and assess the condition. Transformer lifetime depends on the life of its insulation and insulation life is also strongly influenced by moisture in the insulation. Due to importance of this issue, in this paper a new method is introduced for determining the moisture content of the transformer insulation system using dielectric response analysis in the frequency domain based on artificial bee colony algorithm. First, the master curve of dielectric response is modeled. Then, using proposed method the master curve and the measured dielectric response curves are compared. By analyzing the results of the comparison, the moisture content of paper insulation, electrical conductivity of the insulating oil and dielectric model dimensions are determined. Finally, the proposed method is applied to several practical samples to demonstrate its capabilities compared with the well-known conventional method.

  5. Optical and dielectric properties of double helix DNA thin films

    Energy Technology Data Exchange (ETDEWEB)

    Soenmezoglu, Savas, E-mail: svssonmezoglu@kmu.edu.tr [Department of Physics, Faculty of Kamil Ozdag Science, Karamanoglu Mehmetbey University, 70100, Karaman (Turkey); Ates Soenmezoglu, Ozlem [Department of Biology, Faculty of Kamil Ozdag Science, Karamanoglu Mehmetbey University, 70100, Karaman (Turkey)

    2011-12-01

    In this work, the thin film of wheat DNA was deposited by spin-coating technique onto glass substrate, and the optical and dielectric properties of the double helix DNA thin film were investigated. The optical constants such as refractive index, extinction coefficient, dielectric constant, dissipation factor, relaxation time, and optical conductivity were determined from the measured transmittance spectra in the wavelength range 190-1100 nm. Meanwhile, the dispersion behavior of the refractive index was studied in terms of the single oscillator Wemple-DiDomenico (W-D) model, and the physical parameters of the average oscillator strength, average oscillator wavelength, average oscillator energy, the refractive index dispersion parameter and the dispersion energy were achieved. Furthermore, the optical band gap values were calculated by W-D model and Tauc model, respectively, and the values obtained from W-D model are in agreement with those determined from the Tauc model. The analysis of the optical absorption data indicates that the optical band gap E{sub g} was indirect transitions. These results provide some useful references for the potential application of the DNA thin films in fiber optic, solar cell and optoelectronic devices. Highlights: {yields} The optical constants of DNA in full UV-vis spectrum were determined. {yields} The change in optical and dielectric property demonstrates that this material has potential to be used as a novel technology. {yields} DNA shows promise to be more suitable material than other materials currently being used for photonic devices.

  6. Reconstruction of scattering properties of rough air-dielectric boundary

    Science.gov (United States)

    Sokolov, V. G.; Zhdanov, D. D.; Potemin, I. S.; Garbul, A. A.; Voloboy, A. G.; Galaktionov, V. A.; Kirilov, N.

    2016-10-01

    The article is devoted to elaboration of the method of reconstruction of rough surface scattering properties. The object with rough surface is made of transparent dielectric material. Typically these properties are described with bi-directional scattering distribution function (BSDF). Direct measurement of such function is either impossible or very expensive. The suggested solution provides physically reasonable method for the rough surface BSDF reconstruction. The method is based on Monte-Carlo ray tracing simulation for BSDF calculation. Optimization technique is further applied to correctly reconstruct the BSDF. The results of the BSDF reconstruction together with measurement results are presented in the article as well.

  7. The relationship between chemical structure and dielectric properties of plasma-enhanced chemical vapor deposited polymer thin films

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Hao [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States)]. E-mail: hao.jiang@wpafb.af.mil; Hong Lianggou [Materials Sci and Tech Applications, LLC, 409 Maple Springs Drive, Dayton OH 45458 (United States); Venkatasubramanian, N. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Grant, John T. [Research Institute, University of Dayton, 300 College Park, Dayton, OH 45469-0168 (United States); Eyink, Kurt [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Wiacek, Kevin [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Fries-Carr, Sandra [Air Force Research Laboratory, Propulsion Directorate, 1950 Fifth Street, Wright-Patterson Air Force Base, OH 45433-7251 (United States); Enlow, Jesse [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States); Bunning, Timothy J. [Air Force Research Laboratory, Materials Directorate, 3005 Hobson Way, Wright-Patterson Air Force Base, OH 45433-7707 (United States)

    2007-02-26

    Polymer dielectric films fabricated by plasma enhanced chemical vapor deposition (PECVD) have unique properties due to their dense crosslinked bulk structure. These spatially uniform films exhibit good adhesion to a variety of substrates, excellent chemical inertness, high thermal resistance, and are formed from an inexpensive, solvent-free, room temperature process. In this work, we studied the dielectric properties of plasma polymerized (PP) carbon-based polymer thin films prepared from two precursors, benzene and octafluorocyclobutane. Two different monomer feed locations, directly in the plasma zone or in the downstream region (DS) and two different pressures, 80 Pa (high pressure) or 6.7 Pa (low pressure), were used. The chemical structure of the PECVD films was examined by X-ray photoelectron spectroscopy and Fourier-transform infrared spectroscopy. The dielectric constant ({epsilon} {sub r}) and dielectric loss (tan {delta}) of the films were investigated over a range of frequencies up to 1 MHz and the dielectric strength (breakdown voltage) (F {sub b}) was characterized by the current-voltage method. Spectroscopic ellipsometry was performed to determine the film thickness and refractive index. Good dielectric properties were exhibited, as PP-benzene films formed in the high pressure, DS region showed a F{sub b} of 610 V/{mu}m, an {epsilon} {sub r} of 3.07, and a tan {delta} of 7.0 x 10{sup -3} at 1 kHz. The PECVD processing pressure has a significant effect on final film structure and the film's physical density has a strong impact on dielectric breakdown strength. Also noted was that the residual oxygen content in the PP-benzene films significantly affected the frequency dependences of the dielectric constant and loss.

  8. Optical and dielectric properties of ion beam irradiated Ag/polymethyl methacrylate nanocomposites.

    Science.gov (United States)

    Gavade, Chaitali; Singh, N L; Khanna, P K

    2014-08-01

    Changes in the dielectric, optical, structural and thermal properties of PMMA/silver nanocomposites of different concentrations of silver nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of impedance gain phase analyzer, UV-visible spectroscopy, X-ray diffraction and differential scanning calorimetry. Samples were irradiated with 120 MeV Si-ions at fluences of 1 x 10(11), 1 x 10(12) ions/cm2. Dependence of dielectric properties on frequency, ion beam fluence and filler concentration was studied. The results revealed the enhancement in dielectric properties after dopping nanoparticles and also upon irradiation. Optical properties like band gap was estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength region 200-800 nm. It was found that the band gap value shifted to lower energy (from 4.58 eV to 3.21 eV) on doping with silver nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to scissioning of polymer chain due to ion beam irradiation which is also confirmed with XRD analysis.

  9. Disorder driven structural and dielectric properties of silicon substituted strontium titanate

    Science.gov (United States)

    Dugu, Sita; Pavunny, Shojan P.; Sharma, Yogesh; Scott, James F.; Katiyar, Ram S.

    2015-07-01

    A systematic study on structural, microstructural, optical, dielectric, and electrical properties of phase-pure silicon-modified SrTiO3 polycrystalline electroceramics synthesized using high energy solid state reaction techniques is presented. The asymmetry and splitting in the x-ray diffractometer spectra and the observation of first order transverse optical TO2 and longitudinal optical LO4 modes in Raman spectra (nominally forbidden) revealed the distortion in the cubic lattice as a result of breaking of inversion symmetry due to doping. A bandgap Eg of 3.27 eV was determined for the sample by diffuse reflectance spectroscopy. A high dielectric constant of ˜400 and very low dielectric loss of ˜0.03 were obtained at 100 kHz near ambient conditions. The temperature dependence of the dielectric data displayed features of high temperature relaxor ferroelectric behavior as evidence of existence of polar nano-regions. The ac conductivity as a function of frequency showed features typical of universal dynamic response and obeyed a power law σ a c = σ d c + A ω n . The temperature dependent dc conductivity followed an Arrhenius relation with activation energy of 123 meV in the 200-500 K temperature range. The linear dielectric response of Pt/SrSi0.03Ti0.97O3/Pt dielectric capacitors was well characterized. The measured leakage current was exceptionally low, 13 nA/cm2 at 8.7 kV/cm, revealing an interface blocked bulk conduction mechanism.

  10. Study of dielectric and piezoelectric properties of CNT reinforced PZT-PVA 0-3 composite

    Science.gov (United States)

    Vyas, Prince; Prajapat, Rampratap; Manmeeta, Saxena, Dhiraj

    2016-05-01

    Ferroelectric ceramic/polymer composites have the compliance of polymers which overcome the problems of brittleness in ceramics. By imbedding piezoelectric ceramic powder into a polymer matrix, 0-3 composites with good mechanical properties and high dielectric breakdown strength can be developed. The obtained composites of 0-3 connectivity exhibit the piezoelectric properties of ceramics and flexibility, strength and lightness of polymer. These composites can be used in vibration sensing and transducer applications specially as piezoelectric sensors. A potential way to improve piezoelectric& dielectric properties of theses composites is by inclusion of another conductive phase in these composites as reported in the literature. In present work, we prepared PZT-PVA 0-3 composites with 60% ceramic volume fraction reinforced with CNTs with volume ranging from 0 to 1.5 vol%. These CNT reinforced composites were obtained using hot press method with thickness of 200 µm having 0-3 conductivity. These composites were poled applying DC voltage. Dielectric properties of these samples were obtained in a wide frequency range (100 Hz to 1 Mhz) at room temperature. The piezoelectric properties of these composites were analyzed by measuring piezoelectric charge constants (d33). The dielectric and piezoelectric properties of these composites were studied as a function of CNT volume content. In these reinforced composites, CNTs act as a conductive filler dispersed in the matrix which in turn facilitates poling and results in an increase of the piezoelectric properties of the composite due to formation of percolation path through the composites. With a CNT content of 0.3 vol.% in PZT/PVA/CNTs, an increase of 61.3 % was observed in piezoelectric strain factors (d33). In these CNT reinforced composites, a substantial increase (approx. 67%) was also observed in dielectric constant and approximately 89% increase was observed in dielectric loss factor. Results so obtained are in the good

  11. Dielectric loss, conductivity relaxation process and magnetic properties of Mg substituted Ni-Cu ferrites

    Science.gov (United States)

    Singh, Navneet; Agarwal, Ashish; Sanghi, Sujata; Khasa, Satish

    2012-08-01

    The dielectric properties, dc and ac electrical resistivities of Mg substituted Ni-Cu ferrites with general formula Ni0.5Cu0.5-xMgxFe2O4 (0.0≤x≤0.5) have been investigated as a function of frequency, temperature and composition. ac resistivity of all the samples decreases with increase in the frequency exhibiting normal ferrimagnetic behavior. The frequency dependence of dielectric loss tangent showed a maximum in between 10 Hz and 1 kHz in all the ferrites. The conductivity relaxation of the charge carriers was examined using the electrical modulus formulism, and the results indicate the presence of the non-Debye type of relaxation in the prepared ferrites. Similar values of activation energies for dc conduction and for conductivity relaxation reveal that the mechanism of electrical conduction and dielectric polarization is the same in these ferrites. A single 'master curve' for normalized plots of all the modulus isotherms observed for a given composition indicates that the distribution of relaxation time is temperature independent. The saturation magnetization and coercivity as calculated from the hysteresis loop measurement show striking dependence on composition.

  12. Polarization and angle insensitive dual-band bandpass frequency selective surface using all-dielectric metamaterials

    Science.gov (United States)

    Yu, Fei; Wang, Jun; Wang, Jiafu; Ma, Hua; Du, Hongliang; Xu, Zhuo; Qu, Shaobo

    2016-04-01

    In this paper, we demonstrate a dual-band bandpass all-dielectric frequency selective surface (FSS), the building elements of which are high-permittivity ceramic particles rather than metallic patterns. With proper structural design and parameter adjustment, the resonant frequency can be tuned at will. Dual-band bandpass response can be realized due to the coupling between electric and magnetic resonances. As an example, a dual-band bandpass FSS is designed in Ku band, which is composed of two-dimensional periodic arrays of complementary quatrefoil structures (CQS) cut from dielectric plates. Moreover, cylindrical dielectric resonators are introduced and placed in the center of each CQS to broaden the bandwidth and to sharpen the cut-off frequency. Theoretical analysis shows that the bandpass response arises from impedance matching caused by electric and magnetic resonances. In addition, effective electromagnetic parameters and dynamic field distributions are presented to explain the mechanism of impedance matching. The proposed FSS has the merits of polarization independence, stable transmission, and sharp roll-off frequency. The method can also be used to design all-dielectric FSSs with continuum structures at other frequencies.

  13. Pressure-dependent dielectric properties in a polyurethane elastomer

    Science.gov (United States)

    Hwang, Seung Won; Shin, Jae Sup; Shin, Min Jae; Kim, Chy Hyung

    2017-04-01

    The dielectric responses of polyurethane films were investigated in the pressure range from atmospheric to 20 kpsi and in the frequency range from 0.05 Hz to 4 KHz at -50, 0, 29, 50, and 80 ° C, where T g is close to -15 ° C (α-relaxation) and where the glass temperature of the chain extender is about 80 ° C (I-relaxation). When a higher pressure was applied to the material, a lower dielectric constant (k' ) was obtained owing to the suppression of polarization motions by the external pressure. However, k' increased with rising pressure at temperatures above 50 ° C and at high frequencies due to the predominant thermal effect expanding the film outwards, where a dispersive α-relaxation occurred. Both α- and I-relaxations followed the pressure-frequency superposition principle with a different shifting factor, a( p), where the α-relaxation showed a faster migration of the relaxation time with changing pressure and a( p) values larger than those of I-relaxation. The two relaxations observed at 29 ° C demonstrated linear relations between 1/k' and pressure and between ln a( p) and pressure, regardless of the film thickness.

  14. Metal clusters and nanoparticles in dielectric matrices: Formation and optical properties

    Science.gov (United States)

    Gladskikh, I. A.; Vartanyan, T. A.

    2016-12-01

    The optical properties of thin dielectric films with metal inclusions and their dependence on thermal and laser annealing are studied experimentally. Metal clusters (Ag, Au, and Cu) in dielectric materials (Al2O3 and SiO2) are obtained by simultaneous vacuum deposition of metal and dielectric on the surface of a corresponding dielectric substrate (sapphire and quartz). It is shown that, depending on the deposited dielectric material, on the weight ratio of deposited metal and dielectric, and on the subsequent thermal treatment, one can obtain different metal structures, from clusters with a small number of atoms to complex dendritic plasmonic structures.

  15. Tailoring magnetic and dielectric properties of rubber ferrite composites containing mixed ferrites

    Indian Academy of Sciences (India)

    M R Anantharaman; K A Malini; S Sindhu; E M Mohammed; S K Date; S D Kulkarni; P A Joy; Philip Kurian

    2001-12-01

    Rubber ferrite composites containing various mixed ferrites were prepared for different compositions and various loadings. The magnetic and dielectric properties of the fillers as well as the ferrite filled matrixes were evaluated separately. The results are correlated. Simple equations are proposed to predetermine the magnetic and dielectric properties. The validity of these equations is verified and they are found to be in good agreement. These equations are useful in tailoring the magnetic and dielectric properties of these composites with predetermined properties.

  16. Measurement of soil water content with dielectric dispersion frequency

    Science.gov (United States)

    Frequency domain reflectometry (FDR) is an inexpensive and attractive methodology for repeated measurements of soil water content (SWC). Although there are some known measurement limitations for dry soil and sand, a fixed-frequency method is commonly employed using commercially available FDR probes....

  17. Structural and dielectric properties of a complex tungsten bronze ferroelectric

    Science.gov (United States)

    Padhee, R.; Das, P. R.; Parida, B. N.; Choudhary, R. N. P.

    2012-07-01

    The polycrystalline sample of K2Pb2Y2W2Ti4Nb4O30 was synthesized by a mixed-oxide method at high temperature. The compound formation was checked by preliminary X-ray structural analysis. The SEM micrograph exhibits uniform plate and rod-like grain distribution. Detailed studies of variation of dielectric parameters with temperature and frequency, and polarization confirmed the existence of ferroelectricity in the material, with phase transition at 390°C. The ac conductivity follows the Arrhenius equation.

  18. Structural, spectral and dielectric properties of piezoelectric-piezomagnetic composites

    Energy Technology Data Exchange (ETDEWEB)

    Hemeda, O.M., E-mail: omhemeda@yahoo.co.uk [Physics Department, Faculty of Science, Taif University, Al-Hawiah, P.O. Box 888, Taif 21974 (Saudi Arabia); Physics Department, Faculty of Science, Tanta University (Egypt); Tawfik, A.; Amer, M.A. [Physics Department, Faculty of Science, Tanta University (Egypt); Kamal, B.M.; El Refaay, D.E. [Physics Department, Faculty of Science, Suez Canal University (Egypt)

    2012-10-15

    Composite materials of spinel ferrite (SF) NiZnFe{sub 2}O{sub 4} (NZF) and barium titanate (BT) BaTiO{sub 3} were prepared by double sintering ceramic technique. X-ray diffraction patterns for the composite system (1-x) NZF+x BT, showed the presence of mainly of 2 phases, hence confirming the successful preparation of the composite. Some structural and microstructural parameters like porosity, X-ray density, particle size and lattice constant were deduced from the analysis of X-ray data for both phases. Scan electron microscope (SEM) analysis shows nearly a homogeneous microstructure with good dispersion of BT grains as well as the presence of some pores. There was also an enlargement of BT grains with increasing its content. Infra red (IR) spectra of the composite system indicate that BT content affects the intermolecular character of the SF phase. A rise in the dielectric constant occurred at high temperature which was attributed to the effect of space change resulting from the increase of the change carriers in the paramagnetic region. The dielectric loss (tan {delta}) decreased by increasing BT content. - Highlights: Black-Right-Pointing-Pointer Double phase NZF-BT composite has a high magnetoelectric coefficient compared with other materials. Black-Right-Pointing-Pointer This makes it strongly candidates for electromagnetic wave sensors. Black-Right-Pointing-Pointer Addition of BT phase enhance dielectric constant which make it very useful for capacitor industry. Black-Right-Pointing-Pointer Ni ferrite shifts the transition temperature of BT from 120 Degree-Sign C near room temperature. Black-Right-Pointing-Pointer Decrease of dielectric loss which supply with good material with law eddy current loss for cores of t ransformers at microwave frequency.

  19. Dielectric response of wurtzite gallium nitride in the terahertz frequency range

    Science.gov (United States)

    Hibberd, M. T.; Frey, V.; Spencer, B. F.; Mitchell, P. W.; Dawson, P.; Kappers, M. J.; Oliver, R. A.; Humphreys, C. J.; Graham, D. M.

    2016-12-01

    We report on the characterization of the intrinsic, anisotropic, dielectric properties of wurtzite gallium nitride in the spectral range of 0.5-11 THz, using terahertz time-domain spectroscopy. The ordinary (ε˜⊥) and extraordinary (ε˜∥) components of the complex dielectric function were determined experimentally for a semi-insulating, m-plane gallium nitride single crystal, providing measurements of the refractive indices (n⊥,∥) and absorption coefficients (α⊥,∥) . These material parameters were successfully modeled by considering the contribution of the optical phonon modes, measured using Raman spectroscopy, to the dielectric function, giving values for the relative static dielectric constants of ε0⊥ = 9.22 ± 0.02 and ε0∥ = 10.32 ± 0.03 for wurtzite gallium nitride.

  20. Dielectric Characteristics of Microstructural Changes and Property Evolution in Engineered Materials

    Science.gov (United States)

    Clifford, Jallisa Janet

    Heterogeneous materials are increasingly used in a wide range of applications such as aerospace, civil infrastructure, fuel cells and many others. The ability to take properties from two or more materials to create a material with properties engineered to needs is always very attractive. Hence heterogeneous materials are evolving into more complex formulations in multiple disciplines. Design of microstructure at multiple scales control the global functional properties of these materials and their structures. However, local microstructural changes do not directly cause a proportional change to the global properties (such as strength and stiffness). Instead, local changes follow an evolution process including significant interactions. Therefore, in order to understand property evolution of engineered materials, microstructural changes need to be effectively captured. Characterizing these changes and representing them by material variables will enable us to further improve our material level understanding. In this work, we will demonstrate how microstructural features of heterogeneous materials can be described quantitatively using broadband dielectric spectroscopy (BbDS). The frequency dependent dielectric properties can capture the change in material microstructure and represent these changes in terms of material variables, such as complex permittivity. These changes in terms of material properties can then be linked to a number of different conditions, such as increasing damage due to impact or fatigue. Two different broadband dielectric spectroscopy scanning modes are presented: bulk measurements and continuous scanning to measure dielectric property change as a function of position across the specimen. In this study, we will focus on ceramic materials and fiber reinforced polymer matrix composites as test bed material systems. In the first part of the thesis, we will present how different micro-structural design of porous ceramic materials can be captured

  1. Structural, dielectric and magnetic properties of NiFe2O4 prepared via sol-gel auto-combustion method

    Science.gov (United States)

    Sun, Li; Zhang, Ru; Wang, Zhenduo; Ju, Lin; Cao, Ensi; Zhang, Yongjia

    2017-01-01

    Nickelferrite (NiFe2O4)powders were synthesized via sol-gel auto-combustion method and the corresponding temperature dependence of microstructure, dielectric and magnetic properties have been investigated. Results of XRD and SEM indicate that the NiFe2O4 samples exhibit a typical single phase spinel structure and a uniform particle distribution. The dielectric constant and dielectric loss measurements show strong frequency dependence of all the samples. The peak observed in frequency dependence of dielectric loss measurements shifts to higher frequency with the increasing sintering temperature, indicating a Debye-like dielectric relaxation. The remanent magnetization increases with the increasing grain size while the coercivity is just the opposite. The saturation magnetization can achieve 50 emu/g when the sintering temperature is more than 1000 °C, and the lowest coercivity (159.49 Oe) was observed in the NFO sample sintered at 1300 °C for 2 h.

  2. Cross-linking effect on dielectric properties of polypropylene thin films and applications in electric energy storage

    Science.gov (United States)

    Yuan, Xuepei; Chung, T. C. Mike

    2011-02-01

    A family of cross-linked polypropylene (x-PP) thin film dielectrics is systematically studied to understand the cross-linking effect on the dielectric properties. Evidently, the butylstyrene (BSt) cross-linkers increase both the dielectric constant (ɛ) and breakdown strength (E), without increasing energy loss. An x-PP dielectric, with 3.65 mol % BSt cross-linkers, exhibits a ɛ ˜3, which is independent of a wide range of temperatures and frequencies, slim D-E hysteresis loops, high breakdown strength (E=650 MV/m), narrow breakdown distribution, and reliable energy storage capacity >5 J/cm3 (double that of state-of-the-art biaxially oriented polypropylene capacitors), without showing any increase in energy loss.

  3. Dielectric properties of poly(vinylidene fluoride/CaCu3Ti4O12 nanocrystal composite thick films

    Directory of Open Access Journals (Sweden)

    2010-10-01

    Full Text Available The poly(vinylidene fluoride/CaCu3Ti4O12 (CCTO nanocrystal composite films (thickness ≈85 µm with relatively high dielectric permittivity (90 at 100 Hz were prepared by the solution casting followed by spin coating technique. The structural, the microstructural and the dielectric properties of the composites were studied using X-ray diffraction, Scanning Electron Microscope, and Impedance analyzer respectively. The effective dielectric permittivity (εeff of the composite increased with increase in the volume fraction of CCTO at all the frequencies (100 Hz to 1 MHz under investigation. The room temperature dielectric permittivity which is around 90 at 100 Hz, has increased to about 290 at 125°C (100 Hz. These results may be exploited in the development of high energy density capacitors.

  4. Influence of Water Absorption on Volume Resistivity and the Dielectric Properties of Neat Epoxy Material

    KAUST Repository

    Sulaimani, Anwar Ali

    2014-07-15

    Influence of Water Absorption on the Dielectric Properties and Volume Resistivity of Neat Epoxy Material Anwar Ali Sulaimani Epoxy resins are widely used materials in the industry as electrical insulators, adhesives and in aircrafts structural components because of their high mechanical sti ness, strength and high temperature and chemical resistance properties. But still, the in uence of water uptake due to moisture adsorption is not fully understood as it detrimentally modi es the electrical and chemical properties of the material. Here, we investigate the in uence of water moisture uptake on the neat epoxy material by monitoring the change in the volume resistivity and dielectric properties of epoxy material at three di erent thickness con gurations: 0.250 mm, 0.50 mm and 1 mm thicknesses. Gravimetric analysis was done to monitor the mass uptake behaviour, Volume Resistivity was measured to monitor the change in conductivity of the material, and the dielectric properties were mapped to characterise the type of water mechanism available within the material during two ageing processes of sorption and desorption. Two-stage behaviours of di usion and reaction have been identi ed by the mass uptake analysis. Moreover, the plot of volume resistivity versus mass uptake has indi- cated a non-uniform relationship between the two quantities. However, the analysis of the dielectric spectrum at medium range of frequency and time has showed a change 5 in the dipolar activities and also showed the extent to which the water molecules can be segregated between bounding to the resin or existing as free water.

  5. Controlling of dielectrical properties of hydroxyapatite by ethylenediamine tetraacetic acid (EDTA) for bone healing applications.

    Science.gov (United States)

    Kaygili, Omer; Ates, Tankut; Keser, Serhat; Al-Ghamdi, Ahmed A; Yakuphanoglu, Fahrettin

    2014-08-14

    The hydroxyapatite (HAp) samples in the presence of various amounts of ethylenediamine tetraacetic acid (EDTA) were prepared by sol-gel method. The effects of EDTA on the crystallinity, phase structure, chemical, micro-structural and dielectric properties of HAp samples were investigated. With the addition of EDTA, the average crystallite size of the HAp samples is gradually decreased from 30 to 22 nm and the crystallinity is in the range of 65-71%. The values of the lattice parameters (a and c) and volume of the unit cell are decreased by stages with the addition of EDTA. The dielectric parameters such as relative permittivity, dielectric loss and relaxation time are affected by the adding of EDTA. The alternating current conductivity of the as-synthesized hydroxyapatites increases with the increasing frequency and obeys the universal power law behavior. The HAp samples exhibit a non-Debye relaxation mechanism. The obtained results that the dielectrical parameters of the HAp sample can be controlled by EDTA.

  6. Dielectric properties of Ti4+ substituted BaFe12O19 nanoparticles

    Science.gov (United States)

    Ghoneim, A. I.; Amer, M. A.; Meaz, T. M.; Attalah, S. S.

    2017-02-01

    Series of nanocrystalline BaTixFe12-(4/3)xO19 hexagonal ferrites, 0≤x≤1, was prepared using the chemical co-precipitation method. As-prepared samples were heated at 1200 °C for 20 h and slowly cooled to room temperature (RT). XRD studies proved that the samples have single phase M-type hexagonal nanostructure, where their grain size lies in the range of 42.4 - 61.3 nm. Their dielectric properties were studied against temperature (T) and frequency (F). DC conductivity showed increase against T, whereas AC conductivity showed increase with increasing both T and F. This proved the semiconducting behavior of the samples. Activation energies were found to lie in the range of 0.054-0.169 eV for temperature range of RT 373 K and of 0.114-0.274 eV for higher temperatures up to 473 K. Variation of the dielectric constant and AC conductivity against F revealed dispersion in all these hexagonal nanostructures, which was assigned to Maxwell-Wagner type of interfacial polarization. Variation of the dielectric loss tangent against F showed a relaxation spectrum for all samples, whereas the dielectric constant and loss tangent showed an increasing trend against T. The relative magnetic permeability μr showed an increasing trend with temperature.

  7. Broad Microwave Dielectric Property of Single-walled Carbon Nanotube Composites

    Institute of Scientific and Technical Information of China (English)

    Junhua WU

    2008-01-01

    Microwave dielectric measurements over the broad bandwith of 10 MHz to 20 GHz were conducted on composites comprising bundles of single-walled carbon nanotubes (SWNT) embedded in an epoxy matrix, in comparison to the nano-graphite and MWNT. It is found that both relative real and imaginary permittivity of the nanocomposites are strong functions of the SWNT concentration, showing large, wide dielectric and electrical response. Distinct resonance around 1.5 GHz is observed at high SWNT concentrations, accompanied by the downshift of the resonance frequency with increasing concentration. Largely, the SWNT-epoxy composites share the behavior of the MWNT owing to structural similarity, much more effective than the nano-graphite. The remarkable, broadband dielectric and electrical properties of the nanotubes acquired in the work originate from their unique seamless graphene architectures, modeled by two major contributions, dielectric relaxation/resonance and electronic conduction, which is substantiated by the agreement between theoretical analysis and experimental results. The carbon nanotube composites are prospective for microwave applications and offer experimental evidence for fundamental studies in low-dimensional systems.

  8. Effect of swift heavy ion irradiation on dielectrics properties of polymer composite films

    Energy Technology Data Exchange (ETDEWEB)

    Singh, N.L. [Physics Department, M.S. University of Baroda, Vadodara 390002 (India)]. E-mail: singhnl_msu@yahoo.com; Qureshi, Anjum [Physics Department, M.S. University of Baroda, Vadodara 390002 (India)]. E-mail: anjumqur@gmail.com; Singh, F. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India); Avasthi, D.K. [Inter University Accelerator Centre, Aruna Asaf Ali Marg, New Delhi 110067 (India)

    2007-02-25

    Ferric oxalate was used as organometallics fillers in polyvinyl chloride (PVC) to form polymer matrix composite films at different concentration of filler. These films were irradiated with 80 MeV O{sup 6+} ions at the fluences of 1 x 10{sup 11} and 1 x 10{sup 12} ions/cm{sup 2}. The radiation induced modifications in dielectric properties, microhardness, surface morphology and surface roughness of polymer composite films have been investigated at different concentration (i.e. 5%, 10% and 15%) of filler. It was observed that hardness and electrical conductivity of the films increase with the concentration of the dispersed ferric oxalate and also with the fluence. From the analysis of frequency, f, dependence of dielectric constant, {epsilon}, it has been found that the dielectric response in both pristine and irradiated samples obey the Universal law given by {epsilon} {proportional_to} f {sup n-1}. The dielectric constant/loss is observed to change significantly due to the irradiation. This suggests that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Atomic force microscopy (AFM) shows that average roughness (R {sub a}) of the irradiated films is lower than that of unirradiated films. Surface morphology of irradiated polymer composite films is observed to change. Scanning electron microscopy (SEM) results show that partial agglomeration of fillers in the polymer matrix.

  9. Dielectric, electrical transport and magnetic properties of Er3+substituted nanocrystalline cobalt ferrite

    Science.gov (United States)

    Kakade, S. G.; Kambale, R. C.; Kolekar, Y. D.; Ramana, C. V.

    2016-11-01

    Erbium substituted cobalt ferrite (CoFe2-xErxO4; x=0.0-0.2, referred to CFEO) materials were synthesized by sol-gel auto-combustion method. The effect of erbium (Er3+) substitution on the crystal structure, dielectric, electrical transport and magnetic properties of cobalt ferrite is evaluated. CoFe2-xErxO4 ceramics exhibit the spinel cubic structure without any impurity phase for x≤0.10 whereas formation of the ErFeO3 orthoferrite secondary phase was observed for x≥0.15. All the CFEO samples demonstrate the typical hysteresis (M-H) behavior with a decrease in magnetization as a function of Er content due to weak superexchange interaction. The frequency (f) dependent dielectric constant (ε‧) revealed the usual dielectric dispersion. The ε‧-f dispersion (f=20 Hz to 1 MHz) fits to the modified Debye's function with more than one ion contributing to the relaxation. The relaxation time and spread factor derived are ∼10-4 s and ∼0.61(±0.04), respectively. Electrical and dielectric studies indicate that ε‧ increases and the dc electrical resistivity decreases as a function of Er content (x≤0.15). Complex impedance analyses confirm only the grain interior contribution to the conduction process. Temperature dependent electrical transport and room temperature ac conductivity (σac) analyses indicate the semiconducting nature and small polaron hopping.

  10. Refinement of the theory for extracting cell dielectric properties from dielectrophoresis and electrorotation experiments.

    Science.gov (United States)

    Lei, U; Sun, Pei-Hou; Pethig, Ronald

    2011-12-01

    A modified theory is proposed for extracting cell dielectric properties from the peak frequency measurement of electrorotation (ER) and the crossover frequency measurement of dielectrophoresis (DEP). Current theory in the literature is based on the low frequency (DC) approximations for the equivalent cell permittivity and conductivity, which are valid when the measurements are performed in a medium with conductivity less than 1 mS/m. The present theory extracts the cell properties through optimizing an expression for the medium conductivity in terms of the peak ER, or DEP crossover, frequency according to its definition using full expressions of equivalent cell permittivity and conductivity. Various levels of approximation of the theory are proposed and discussed through a scaling analysis. The present theory can extract both membrane and interior properties from the low and the high peak ER, or DEP crossover, frequencies for any medium conductivity provided the peak ER, or DEP crossover, frequency exists. It can be reduced to the linear theory for the low peak ER and DEP crossover frequencies in the literature when the medium conductivity is less than 10 mS/m. However, we can determine the membrane capacitance and conductance via the slope and intercept, respectively, of the straight line fitting of the ER peak and DEP frequency against medium conductivity data according to the linear theory only when the intercept dominates the experimental uncertainty, which occurs when the medium conductivity is less than 1 mS/m in practice.

  11. Dielectric Properties of Compatibilised EPDM/Silicone rubber Nanocomposites

    Directory of Open Access Journals (Sweden)

    Vijayalekshmi Vijayakumar

    2017-06-01

    Full Text Available EPDM/Silicone rubber nanocomposites are prepared by incorporating various phr of organically modified montmorillonite (OMMT nanoclay onto compatibilised and uncompatibilised EPDM/Silicone rubber blends using two roll mill. Compatibilisation of EPDM and Silicone rubber blend is achieved through insitu grafting of silane onto EPDM during mixing of rubbers. Effect of OMMT content and compatibilisation of blend system on electrical, mechanical and thermal properties of the nanocomposites are investigated. The results obtained for various properties indicate that the compatibilised EPDM/Silicone rubber nanocomposites have improved dielectric, mechanical and thermal properties compared to that of uncompatibilised blend nanocomposites. It is observed that, the addition of OMMT upto 5 phr onto both compatibilised and uncompatibilised blends of EPDM/Silicone offers significant improvement in the above mentioned properties. Increasing content of OMMT onto the blends cause marked enhancement in thermal stability of the nanocomposties. Transmission electron micrographs shows the compatibility between EPDM and silicone rubbers in the blend and the exfoliation of OMMT layers in the matrix phase. The present work reveals that the compatibilised EPDM/ Silicone/ OMMT nanocomposite can be a better candidate for high voltage electrical insulation due to its enhanced dielectric, mechanical and themal characteristics.

  12. Dielectric properties of electron irradiated PbZrO3 thin films

    Indian Academy of Sciences (India)

    Shetty Aparna; V M Jali; Ganesh Sanjeev; Jayanta Parui; S B Krupanidhi

    2010-06-01

    The present paper deals with the study of the effects of electron (8 MeV) irradiation on the dielectric and ferroelectric properties of PbZrO3 thin films grown by sol–gel technique. The films were (0.62 m thick) subjected to electron irradiation using Microtron accelerator (delivered dose 80, 100, 120 kGy). The films were well crystallized prior to and after electron irradiation. However, local amorphization was observed after irradiation. There is an appreciable change in the dielectric constant after irradiation with different delivered doses. The dielectric loss showed significant frequency dispersion for both unirradiated and electron irradiated films. c was found to shift towards higher temperature with increasing delivered dose. The effect of radiation induced increase of ′() is related to an internal bias field, which is caused by radiation induced charges trapped at grain boundaries. The double butterfly loop is retained even after electron irradiation to the different delivered doses. The broader hysteresis loop seems to be related to radiation induced charges causing an enhanced space charge polarization. Radiation-induced oxygen vacancies do not change the general shape of the AFE hysteresis loop but they increase s of the hysteresis at the electric field forced AFE to FE phase transition. We attribute the changes in the dielectric properties to the structural defects such as oxygen vacancies and radiation induced charges. The shift in c, increase in dielectric constant, broader hysteresis loop, and increase in r can be related to radiation induced charges causing space charge polarization. Double butterfly and hysteresis loops were retained indicative of AFE nature of the films.

  13. Effect of substitution group on dielectric properties of 4H-pyrano [3, 2-c] quinoline derivatives thin films

    Science.gov (United States)

    H, M. Zeyada; F, M. El-Taweel; M, M. El-Nahass; M, M. El-Shabaan

    2016-07-01

    The AC electrical conductivity and dielectrical properties of 2-amino-6-ethyl-5-oxo-4-(3-phenoxyphenyl)-5,6-dihydro-4H-pyrano[3, 2-c]quinoline-3-carbonitrile (Ph-HPQ) and 2-amino-4-(2-chlorophenyl)-6-ethyl-5-oxo-5,6-dihydro-4H-pyrano [3, 2-c] quinoline-3-carbonitrile (Ch-HPQ) thin films were determined in the frequency range of 0.5 kHz-5 MHz and the temperature range of 290-443 K. The AC electrical conduction of both compounds in thin film form is governed by the correlated barrier hopping (CBH) mechanism. Some parameters such as the barrier height, the maximum barrier height, the density of charges, and the hopping distance were determined as functions of temperature and frequency. The phenoxyphenyl group has a greater influence on those parameters than the chlorophenyl group. The AC activation energies were determined at different frequencies and temperatures. The dielectric behaviors of Ph-HPQ and Ch-HPQ were investigated using the impedance spectroscopy technique. The impedance data are presented in Nyquist diagrams for different temperatures. The Ch-HPQ films have higher impedance than the Ph-HPQ films. The real dielectric constant and dielectric loss show a remarkable dependence on the frequency and temperature. The Ph-HPQ has higher dielectric constants than the Ch-HPQ.

  14. Influence of Fabrication Parameters on the Phase Formation and Dielectric Properties of CaCu3Ti4012 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Qian Zheng; Huiqing Fant

    2012-01-01

    The giant dielectric permittivity materials CaCu3Ti4012 (CCTO) were synthesized by conventional solid-state reaction techniques. X-ray diffraction and Raman scattering for the powder indicate that the powder calcined at 950 ℃ for 12 h has been completely transformed into the purer CCTO phase. Furthermore, the morphology and size of the grains of the ceramics sintered at 1090 ℃ in the dwell time range from 0 to 26 h were observed by scanning electron microscopy (SEM). Dielectric properties of the polycrystalline CCTO ceramics were characterized in a broad frequency range (100 Hz-1 MHz) and at a temperature ranged from 300 to 500 K. The longer sintering time may lead to more defect structures and the enhanced conductivity, also leads to substantial improvements in permittivity. Grain size and density differences were not large enough to account for the enhancement in dielectric permittivity. Based on the observations, it is believed that the primary factor affecting dielectric behavior is the development of internal defects. The CCTO ceramics sintered at 1090 ℃ for 15 h exhibit lower dielectric loss (-0.05) near room temperature, and the dielectric relaxation behavior above 1 kHz was observed to follow the Arrhenius law. The activation energy (Ea) of 0.65 eV indicates that the doubly ionized oxygen vacancies in the grain boundaries are responsible for the dielectric relaxation of the CCTO ceramics.

  15. Fabrication and Dielectric Properties of AlN Filled Epoxy Nano-composites

    Energy Technology Data Exchange (ETDEWEB)

    Gao Naiui; Yu Xin; Jin Haiyun; He Bo; Dong Pu [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an, 710049 (China); Gao Chao, E-mail: hyjin@mail.xjtu.edu.cn

    2011-10-29

    Epoxy resins were materials with excellent mechanical, electrical properties and good chemical stability. Thus, they had been used in various fields, especially in electrical and electronic application. However, because they were brittle material, the fields of application were limited. Adding nano-Aluminum Nitride (AlN) into Epoxy resins could improve the toughness of the composites, the thermal behaviors of composites could also be improved, but the influence on dielectric properties was not very clear. In this research, epoxy resin based composites were fabricated. The relationships between the dielectric properties and the nano-AlN particle content were investigated. The results showed that, both relative permittivity ({epsilon}{sub r}) and dielectric loss tangent (tan{delta}) decreased to be less than that of monolithic epoxy when nano-AlN particle content was no more than certain amount, the DC volume resistivity ({rho}{sub v}) and low frequency resistivity decreased with increasing nano-AlN content (in certain range of content). AC breakdown strength (E{sub B}) did not have an obvious tendency with nano-AlN content.

  16. THz - ToF Optical Layer Analysis (OLA) to determine optical properties of dielectric materials

    Science.gov (United States)

    Spranger, Holger; Beckmann, Jörg

    2017-02-01

    Electromagnetic waves with frequencies between 0.1 and 10 THz are described as THz-radiation (T-ray). The ability to penetrate dielectric materials makes T-rays attractive to reveal discontinuities in polymer and ceramic materials. THz-Time Domain Spectroscopy Systems (THz-TDS) are available on the market today which operates with THz-pulses transmitted and received by optically pumped semiconductor antennas. In THz-TDS the travelling time (ToF) and shape of the pulse is changed if it interacts with the dielectric material and its inherent discontinuities. A tomogram of the object under the test can be reconstructed from time of flight diffraction (ToFD) scans if a synthetic focusing aperture (SAFT) algorithm is applied. The knowledge of the base materials shape and optical properties is essential for a proper reconstruction result. To obtain these properties a model is assumed which describes the device under the test as multilayer structure composed of thin layers with different dielectric characteristics. The Optical Layer Analysis (OLA) is able to fulfill these requirements. A short description why the optical properties are crucial for meaningful SAFT reconstruction results will be given first. Afterwards the OLA will be derived and applied on representative samples to discuss and evaluate its benefits and limits.

  17. Effect of calcining temperature on electrical and dielectric properties of cadmium stannate

    Energy Technology Data Exchange (ETDEWEB)

    Sawant, V.S.; Shinde, S.S.; Deokate, R.J.; Bhosale, C.H.; Chougule, B.K. [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004 (India); Rajpure, K.Y., E-mail: rajpure@yahoo.com [Electrochemical Materials Laboratory, Department of Physics, Shivaji University, Kolhapur 416004 (India)

    2009-04-15

    The cadmium stannate samples were prepared by chemical co-precipitation method using stannic chloride pentahydrate (SnCl{sub 4}.5H{sub 2}O) and cadmium chloride (CdCl{sub 2}) as precursors by carefully controlling the preparative parameters. The effect of calcining temperature on the phase, microstructure, morphological and electrical properties of cadmium stannate has been investigated. The X-ray diffraction patterns indicate the conversion of rhombohedral to spinel cubic crystal structure and polycrystallinity of the samples. SEM study of Cd{sub 2}SnO{sub 4} sample shows randomly distributed cubic crystals of varying sizes. The dc resistivity was measured as a function of temperature. The dielectric constant and dielectric loss were studied as a function of frequency. To understand the conduction mechanism in the samples AC conductivity was measured.

  18. Optical properties of metallo-dielectric microspheres in opal structures

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y; Whitehouse, C; Li, Jensen; Tam, Wing Yim; Chan, C T; Sheng Ping [Department of Physics, Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2003-09-03

    We report the fabrication of opal structure using metallo-dielectric silica microspheres. Mono-dispersed silica microspheres were coated with silver using an electrode-less wet-plating technique. Thin slabs of opal were obtained by assembling the silver-coated microspheres between two glass plates using a forced-packing method. The optical properties of the resulting opal structure were studied in the infrared range. Good agreement is obtained with the predictions of a multiple scattering approach, provided that the silver layer is modelled as a silver composite.

  19. The dielectric calibration of capacitance probes for soil hydrology using an oscillation frequency response model

    Directory of Open Access Journals (Sweden)

    D. A. Robinson

    1998-01-01

    Full Text Available Capacitance probes are a fast, safe and relatively inexpensive means of measuring the relative permittivity of soils, which can then be used to estimate soil water content. Initial experiments with capacitance probes used empirical calibrations between the frequency response of the instrument and soil water content. This has the disadvantage that the calibrations are instrument-dependent. A twofold calibration strategy is described in this paper; the instrument frequency is turned into relative permittivity (dielectric constant which can then be calibrated against soil water content. This approach offers the advantages of making the second calibration, from soil permittivity to soil water content. instrument-independent and allows comparison with other dielectric methods, such as time domain reflectometry. A physically based model, used to calibrate capacitance probes in terms of relative permittivity (εr is presented. The model, which was developed from circuit analysis, predicts, successfully, the frequency response of the instrument in liquids with different relative permittivities, using only measurements in air and water. lt was used successfully to calibrate 10 prototype surface capacitance insertion probes (SCIPS and a depth capacitance probe. The findings demonstrate that the geometric properties of the instrument electrodes were an important parameter in the model, the value of which could be fixed through measurement. The relationship between apparent soil permittivity and volumetric water content has been the subject of much research in the last 30 years. Two lines of investigation have developed, time domain reflectometry (TDR and capacitance. Both methods claim to measure relative permittivity and should therefore be comparable. This paper demonstrates that the IH capacitance probe overestimates relative permittivity as the ionic conductivity of the medium increases. Electrically conducting ionic solutions were used to test the

  20. Structural, dielectric and ferroelectric properties of PLZFNT ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Parveen, E-mail: parveenpaliwal@gmail.com [PG Department of Physics, GVM Girls College, Sonepat 131001 (India); Singh, Pratibha [Electroceramics Research Lab, GVM Girls College, Sonepat 131001 (India); Juneja, J.K., E-mail: jk_juneja@yahoo.com [Department of Physics, Hindu College, Sonepat 131001 (India); Raina, K.K. [School of Physics and Materials Science, Thapar University, Patiala 147004 (India); Pant, R.P. [National Physical Laboratories, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Prakash, Chandra [Solid State Physics Laboratory, Lucknow Road, Delhi 110054 (India); Singh, Sangeeta [Department of Physics, GVM Girls College, Sonepat 131001 (India)

    2014-07-15

    Highlights: • Maximum relative density (95.64%) and Pr (52 μC/cm{sup 2}) can be observed for x = 0.02. • P{sub r}/P{sub s} ratio indicating squareness of the PE loop found to be maximum for x = 0.015. • P{sub r}/P{sub s} = 0.83 is not reported in the literature for the PZT ceramics. - Abstract: Here we are reporting the structural, dielectric and ferroelectric properties of PLZFNT ceramic having compositional formula Pb{sub 1−1.5x}La{sub x}Zr{sub 0.588}Ti{sub 0.392}Fe{sub 0.01}Nb{sub 0.01}O{sub 3} (x = 0–0.02 in steps of 0.005). Samples were prepared by solid state route. The structural, dielectric and ferroelectric properties are studied as a function of La content. X-ray diffraction (XRD) analysis reveals pure perovskite tetragonal structure for all the compositions. There is drastic improvement in ferroelectric properties with La substitution. Ratio of remnant to spontaneous polarization (P{sub r}/P{sub s}) which indicates the measure of squareness of the PE loop is found to improve with the increase in La content.

  1. Investigation of dielectric behavior of water and thermally aged of XLPE/BaTiO3 composites in the low-frequency range

    Science.gov (United States)

    Madani, Lakhdar; Belkhiat, Saad; Berrag, Amine; Nemdili, Saad

    2015-10-01

    Cross-Linked Polyethylene (XLPE) is widely used as insulation in electrical engineering, especially as cable insulation sheaths. In order to improve the dielectric properties susceptible to be modified under the effects of thermal aging and water in an absorption environment, polymers are mixed with ceramics. In this paper, the influence of barium titanate (BaTiO3), on the dielectric properties of XLPE has been studied. Dielectric parameters have been measured using an impedance analyzer RLC (WAYNE KERR 6420 type). Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy and X-ray diffraction were used as characterization techniques. The study has been carried out on two samples of XLPE. A pure sample of each were studied as a unloaded samples to be compared with samples of 5%wt, 10%wt, 15%wt and 20%wt. BaTiO3 loaded XLPE. Afterwards, the composites were subject to humidity and to thermal aging. The incorporation of BaTiO3 1∘C does not modify the crystallinity and morphology of the XLPE and 2∘C reduces the space charges therefore the dielectric losses. tgδ, ɛr and loss index are measured. Frequency response analysis has been followed in the frequency range (20-300 Hz). Experimental results show well that BaTiO3 as nano-filler improves the dielectric properties of XLPE but in excessive content can drive to the cracking and therefore to absorption of water.

  2. A facile growth mechanism, structural, optical, dielectric and electrical properties of ZnSe nanosphere via hydrothermal process

    Science.gov (United States)

    Javed, Qurat-Ul-Ain; Baqi, Sabah; Abbas, Hussain; Bibi, Maryam

    2017-02-01

    Hydrothermal method was chosen as a convenient method to fabricate zinc selenide (ZnSe) nanoparticle materials. The prepared nanospheres were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), where its different properties were observed using UV-visible spectroscopy and LCR meter. It was found that the pure ZnSe nanoparticles have a Zinc blende structure with crystallite size 10.91 nm and in a spherical form with average diameter of 35 nm (before sonication) and 18 nm (after sonication) with wide band gap of 4.28 eV. It was observed that there is inverse relation of frequency with dielectric constant and dielectric loss while AC conductivity grows up by increasing frequency. Such nanostructures were determined to be effectively used in optoelectronic devices as UV detector and in those devices where high-dielectric constant materials are required.

  3. Processing dependent properties of silica xerogels for interlayer dielectric applications

    Science.gov (United States)

    Jain, Anurag

    One of the current and near future research focus in microelectronics is to integrate copper with a new low dielectric constant (K) material. The traditional low K is dense SiO2 (K = 4). Introducing porosity in materials with silica backbone is promising as processing and integration methods are well known. This thesis focuses on studying silica xerogel, also known as nanoporous silica. A new low-K material has to be tested for an array of electrical, mechanical, thermal, and chemical properties before it is deemed successful to replace dense SiO2. These properties of silica xerogels are characterized using various analytical techniques and the effect of processing conditions is studied. The property data is explained by the models and mechanisms relating processing-structure-property behavior. The processing effects on thermal and mechanical properties are studied in great detail and the theories for generic porous low-K materials are developed. The xerogel films are processed at ambient conditions and crack free, thick (0.5--4 mum), highly porous (˜25--90%) films are obtained. Two methods of porosity control were used. One is the traditional single solvent (ethanol) method and another is a binary solvent (mixture of ethanol and ethylene glycol) method. The films underwent aging and silylation procedures to make the backbone stiff and hydrophobic. Sintering of xerogel films eliminates defects and organics and additional condensation reactions make matrix more connected, dense and ordered. Films were characterized for their refractive index, thickness, porosity, pore size and surface roughness. Dielectric constant measurements at 1 MHz show that K varies linearly with porosity. Dielectric loss tangents are low and breakdown strength meets the standards. FTIR and XPS analysis show that films are stable chemically and remain hydrophobic even after boiling in water. Mechanical and thermal properties of porous materials are dependent on the microstructure and various

  4. Composition dependence of dielectric properties in Se{sub 100-x}Cu{sub x} glassy alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, J.; Shrotriya, D.; Kumar, S., E-mail: dr-santosh-kr@yahoo.com [Department of Physics, Christ Church College, Kanpur-208001 (India)

    2015-06-24

    In this paper we report the composition dependent of dielectric properties in Se{sub 100-x}Cu{sub x} (x = 0, 2, 4 and 6) glassy alloys. The temperature and frequency dependence of the dielectric constants and the dielectric losses in the above glassy systems in the frequency range (1k Hz-5 M Hz) and temperature range (300 K–350 K) have been measured. It has been found that dielectric constant and the dielectric loss both are highly dependent on frequency and temperature and also found to increase with increasing concentration of Cu in pure amorphous Se. The role of Cu, as an impurity in the pure a-Se glassy alloy, is also discussed in terms of electronegativity difference between the elements used in making the aforesaid glassy system. Apart from this, the results have been also correlated in terms of a dipolar model which considers the hopping of charge carriers over a potential barrier between charged defect states.

  5. Effect of Dielectric Properties of a Solvent-Water Mixture Used in Microwave-Assisted Extraction of Antioxidants from Potato Peels.

    Science.gov (United States)

    Singh, Ashutosh; Nair, Gopu Raveendran; Liplap, Pansa; Gariepy, Yvan; Orsat, Valerie; Raghavan, Vijaya

    2014-02-24

    The dielectric properties of a methanol-water mixture were measured at different temperatures from 20 to 80 °C at two frequencies 915 MHz and 2450 MHz. These frequencies are most commonly used on industrial and domestic scales respectively. In this study, the dielectric properties of a methanol-water mixture were found to be dependent on temperature, solvent concentration, and presence of plant matrix. Linear and quadratic equations were developed to establish the dependency between factors. At 2450 MHz, the dielectric constant of methanol-water mixtures was significantly affected by concentration of methanol rather than by temperature, whereas the dielectric loss factor was significantly affected by temperature rather than by methanol concentration. Introduction of potato peel led to an increase in the effect of temperature on the dielectric properties of the methanol fractions. At 915 MHz, both the dielectric properties were significantly affected by the increase in temperature and solvent concentration, while the presence of potato peel had no significant effect on the dielectric properties. Statistical analysis of the dissipation factor at 915 and 2450 MHz revealed that both temperature and solvent concentration had a significant effect on it, whereas introduction of potato peels at 915 MHz reduced the effect of temperature as compared to 2450 MHz. The total phenolic yield of the microwave-assisted extraction process was significantly affected by the solvent concentration, the dissipation factor of the methanol-water mixture and the extraction time.

  6. Effect of Dielectric Properties of a Solvent-Water Mixture Used in Microwave-Assisted Extraction of Antioxidants from Potato Peels

    Directory of Open Access Journals (Sweden)

    Ashutosh Singh

    2014-02-01

    Full Text Available The dielectric properties of a methanol-water mixture were measured at different temperatures from 20 to 80 °C at two frequencies 915 MHz and 2450 MHz. These frequencies are most commonly used on industrial and domestic scales respectively. In this study, the dielectric properties of a methanol-water mixture were found to be dependent on temperature, solvent concentration, and presence of plant matrix. Linear and quadratic equations were developed to establish the dependency between factors. At 2450 MHz, the dielectric constant of methanol-water mixtures was significantly affected by concentration of methanol rather than by temperature, whereas the dielectric loss factor was significantly affected by temperature rather than by methanol concentration. Introduction of potato peel led to an increase in the effect of temperature on the dielectric properties of the methanol fractions. At 915 MHz, both the dielectric properties were significantly affected by the increase in temperature and solvent concentration, while the presence of potato peel had no significant effect on the dielectric properties. Statistical analysis of the dissipation factor at 915 and 2450 MHz revealed that both temperature and solvent concentration had a significant effect on it, whereas introduction of potato peels at 915 MHz reduced the effect of temperature as compared to 2450 MHz. The total phenolic yield of the microwave-assisted extraction process was significantly affected by the solvent concentration, the dissipation factor of the methanol-water mixture and the extraction time.

  7. Molecular dynamics simulation of liquid water confined inside graphite channels: dielectric and dynamical properties.

    Science.gov (United States)

    Martí, J; Nagy, G; Guàrdia, E; Gordillo, M C

    2006-11-30

    Electric and dielectric properties and microscopic dynamics of liquid water confined between graphite slabs are analyzed by means of molecular dynamics simulations for several graphite-graphite separations at ambient conditions. The electric potential across the interface shows oscillations due to water layering, and the overall potential drop is about -0.28 V. The total dielectric constant is larger than the corresponding value for the bulklike internal region of the system. This is mainly due to the preferential orientations of water nearest the graphite walls. Estimation of the capacitance of the system is reported, indicating large variations for the different adsorption layers. The main trend observed concerning water diffusion is 2-fold: on one hand, the overall diffusion of water is markedly smaller for the closest graphite-graphite separations, and on the other hand, water molecules diffuse in interfaces slightly slower than those in the bulklike internal areas. Molecular reorientational times are generally larger than those corresponding to those of unconstrained bulk water. The analysis of spectral densities revealed significant spectral shifts, compared to the bands in unconstrained water, in different frequency regions, and associated to confinement effects. These findings are important because of the scarce information available from experimental, theoretical, and computer simulation research into the dielectric and dynamical properties of confined water.

  8. Influence of titanium chloride addition on the optical and dielectric properties of PVA films

    Energy Technology Data Exchange (ETDEWEB)

    Abdelaziz, M., E-mail: mabdelaziz62@yahoo.co [Science Department, Community College of Riyadh, King Saudi University, P.O. Box 28095, Riyadh 11437 (Saudi Arabia); Physics Department, Faculty of Sciences, Mansoura University, Mansoura 35516 (Egypt); Ghannam, Magdy M. [Physics and Astronomy Department, Faculty of Science, King Saudi University, P.O. Box 2454, Riyadh 11451 (Saudi Arabia)

    2010-02-01

    Polymeric films based on polyvinyl alcohol (PVA) doped with titanium chloride (TiCl{sub 3}) at different weight percent ratios were prepared using the solvent cast technique. The structural properties of these polymeric films are examined by XRD and FTIR studies. The complexation of the dopant with the polymer was confirmed by FTIR studies. The XRD pattern reveals that the amorphous domains of PVA polymer matrix increased with raising the TiCl{sub 3} content. The optical properties of these polymeric films were examined by optical absorption and emission spectroscopy. Electrical conductivity was measured at room temperature of pure PVA and PVA doped with different concentrations of TiCl{sub 3} from 20 Hz to 3 MHz. The conductivity was found to increase with the increase in dopant concentration. The dielectric constant (epsilon') indicates a strong dielectric dispersion in the studied frequency range and increases as dopant content increases. This increase in both sigma and epsilon' is attributed to the increase in the localized charges distribution. Moreover, a loss peak was identified in the dielectric loss spectra and it is attributed to the orientation of polar groups.

  9. Insight into the electrical properties and chain conformation of spherical polyelectrolyte brushes by dielectric spectroscopy

    Science.gov (United States)

    Guo, Xiaoxia; Zhao, Kongshuang

    2017-02-01

    We report here a dielectric study on three kinds of anionic spherical polyelectrolyte brush (SPBs, consisting of a polystyrene (PS) core and three different poly (acrylic acid) chains grafted onto the core) suspensions over a frequency ranging from 40 Hz to 110 MHz. The relaxation behavior of the SPB suspensions shows significant changes in the brush-layer properties when the mass fraction of SPBs and the pH of the suspensions change. Two definite relaxations related to the interfacial polarization are observed around 100 kHz and 10 MHz. A single-layer spherical-shell model is applied to describe the SPB suspensions wherein the suspended SPB is modeled as a spherical-shell composite particle in which an insulated PS sphere is surrounded by a conducting ion-permeable shell (the polyelectrolyte chain layer). We developed the curve-fitting procedure to analyze the dielectric spectrum in order to obtain the dielectric properties of the components of the SPBs, especially the properties of the polyelectrolyte brush. Based on this method and model, the permittivity and conductivity of the brush layer, ζ potential, etc are calculated. The ordered orientation of the water molecules in the layer leads to an additional electrical dipole moment; increasing pH causes the brush layer to swell. In addition, the repulsive force between the SPB particles are evaluated using the brush-layer thickness, which is obtained by fitting dielectric spectra, combined with relative theoretical formulas. Increasing PH values or SPB concentration would improve the stability of the SPBs dispersion.

  10. Conversion of Dielectric Data from the Time Domain to the Frequency Domain

    Directory of Open Access Journals (Sweden)

    Vladimir Durman

    2005-01-01

    Full Text Available Polarisation and conduction processes in dielectric systems can be identified by the time domain or the frequency domain measurements. If the systems is a linear one, the results of the time domain measurements can be transformed into the frequency domain, and vice versa. Commonly, the time domain data of the absorption conductivity are transformed into the frequency domain data of the dielectric susceptibility. In practice, the relaxation are mainly evaluated by the frequency domain data. In the time domain, the absorption current measurement were prefered up to now. Recent methods are based on the recovery voltage measurements. In this paper a new method of the recovery data conversion from the time the frequency domain is proposed. The method is based on the analysis of the recovery voltage transient based on the Maxwell equation for the current density in a dielectric. Unlike the previous published solutions, the Laplace fransform was used to derive a formula suitable for practical purposes. the proposed procedure allows also calculating of the insulation resistance and separating the polarisation and conduction losses.

  11. Constitutional Design and Dielectric Properties of BST Graded Ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHU Jing-chuan; CHENG Hua-rong; WU Shu-yan; JEON Jae-ho

    2004-01-01

    The effect of B2O3 dopant and SrTiO3 (ST) content on lattice parameters and ferro-paraelectric phase transition temperature (i.e. Curie point) of Ba1-xSrxTiO3 (BST, x=0~0.4) ceramics was investigated, and then BST graded ceramics with controllable transition temperature zone were fabricated and characterized for their dielectric properties. The results show that with the increase of ST content, c/a ratio and Curie point of both doped and undoped ceramics decreased linearly but with different rate of change, resulting from different ionic radiuses of Ba2+, Sr2+ and B3+. Moreover, both c/a ratio and Curie point of doped BST increased slightly in comparison with that of undoped ones while the Curie point changed scarcely with dopant amount rising, which perhaps means that for BST grains with different ST content, B2O3 solubility was different but limited and most of boron (B) did not incorporate into BST grains. Through controlling composition,transition temperature of graded ceramics can be designed. For doped graded ceramics sintered at 1250℃, its dielectric properties was much better than that of undoped one sintered at 1400℃, and Curie peak of both samples was broadened effectively via graded structure.

  12. A genetic algorithm for optimizing multi-pole Debye models of tissue dielectric properties

    Science.gov (United States)

    Clegg, J.; Robinson, M. P.

    2012-10-01

    Models of tissue dielectric properties (permittivity and conductivity) enable the interactions of tissues and electromagnetic fields to be simulated, which has many useful applications in microwave imaging, radio propagation, and non-ionizing radiation dosimetry. Parametric formulae are available, based on a multi-pole model of tissue dispersions, but although they give the dielectric properties over a wide frequency range, they do not convert easily to the time domain. An alternative is the multi-pole Debye model which works well in both time and frequency domains. Genetic algorithms are an evolutionary approach to optimization, and we found that this technique was effective at finding the best values of the multi-Debye parameters. Our genetic algorithm optimized these parameters to fit to either a Cole-Cole model or to measured data, and worked well over wide or narrow frequency ranges. Over 10 Hz-10 GHz the best fits for muscle, fat or bone were each found for ten dispersions or poles in the multi-Debye model. The genetic algorithm is a fast and effective method of developing tissue models that compares favourably with alternatives such as the rational polynomial fit.

  13. A genetic algorithm for optimizing multi-pole Debye models of tissue dielectric properties.

    Science.gov (United States)

    Clegg, J; Robinson, M P

    2012-10-01

    Models of tissue dielectric properties (permittivity and conductivity) enable the interactions of tissues and electromagnetic fields to be simulated, which has many useful applications in microwave imaging, radio propagation, and non-ionizing radiation dosimetry. Parametric formulae are available, based on a multi-pole model of tissue dispersions, but although they give the dielectric properties over a wide frequency range, they do not convert easily to the time domain. An alternative is the multi-pole Debye model which works well in both time and frequency domains. Genetic algorithms are an evolutionary approach to optimization, and we found that this technique was effective at finding the best values of the multi-Debye parameters. Our genetic algorithm optimized these parameters to fit to either a Cole-Cole model or to measured data, and worked well over wide or narrow frequency ranges. Over 10 Hz-10 GHz the best fits for muscle, fat or bone were each found for ten dispersions or poles in the multi-Debye model. The genetic algorithm is a fast and effective method of developing tissue models that compares favourably with alternatives such as the rational polynomial fit.

  14. Study on the Thermal and Dielectric Properties of SrTiO3/Epoxy Nanocomposites

    Directory of Open Access Journals (Sweden)

    Xiaoxing Zhang

    2017-05-01

    Full Text Available SrTiO3/epoxy nanocomposites are prepared using the facile solution-processing technique by incorporating SrTiO3 nanoparticles with different weight fractions into the epoxy resin host. The morphology of the nanoparticles and composites, as well as the thermal conduction characteristics and electrical properties of the composites were investigated via conventional testing methods. The thermal conductivity increased along with the SrTiO3 weight fractions, and the thermal conductivity of the SrTiO3/epoxy composite with 40 wt % weight fraction increased to 0.52 W/mK. The dielectric constant increased along with the weight fractions and decreased along with frequency, thereby suggesting that the interfacial and dipole polarization do not follow the changes in the electrical field direction at high frequency. The dielectric constants at 1 kHz frequency increased along with temperature. Surface breakdown tests illustrated further improvements in the thermal and electrical properties of the composites. In the same time span of 40 s, the 40 wt % nanocomposite demonstrated a rapid temperature decline rate of 6.77 °C/s, which was 47% faster than that of the pure epoxy sample. The surface breakdown voltage also increased along with the weight fractions. The functional composites can solve the key problem in the intelligentization, miniaturization, and high-efficiency of the gas-insulated switchgear, which warrants further research.

  15. Characterisation of water behaviour in cellulose ether polymers using low frequency dielectric spectroscopy.

    Science.gov (United States)

    McCrystal, C B; Ford, J L; He, R; Craig, D Q M; Rajabi-Siahboomi, A R

    2002-08-28

    The behaviour of water in hydroxypropylmethylcellulose (HPMC) K100LV, K4M, K15M, K100M, E4M, F4M and HPC polymers was characterised using low frequency dielectric spectroscopy (LFDS). Dielectric responses of 25% (w/w) HPMC K15M gels and deionised water were found to be similar at +22 and 0 degrees C. However, at -30 degrees C, a dielectric response typical of a solid was apparent. The melting of frozen water within gels was detected as increases in the magnitude of the dielectric response with increase in temperature. More than one phase transition was visible in the majority of gels studied which may be related to the presence of different states of water melting at different temperatures. In addition to polymer concentration, both polymer molecular weight and substitution level influenced the nature of the transitions. The magnitude of the dielectric response was increased in all HPMC gel systems in comparison to the response seen in deionised water. Drug addition affected the transitions occurring during the melting of ice in the gels. This may be related to the presence of ionic species in the systems. LFDS studies on cellulose ether gels have provided some interesting evidence for the existence of more than one state of water within such gel systems. The results are in good agreement with thermal analysis findings in similar gel systems.

  16. AC Conductivity and Dielectric Properties of Borotellurite Glass

    Science.gov (United States)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  17. Microwave Brightness Temperature and Lunar Son Dielectric Property Retrieve

    Institute of Scientific and Technical Information of China (English)

    J. Wu; D.H. Li; A.T. Altyntsev; B.I. Lubyshev

    2005-01-01

    Among many scientific objectives of lunar exploration, investigations on lunar soil become more and more attractive to the scientists duo to the existence of abundant 3He and ilmenite in the lunar soil and their possible utilization. Although the soil composition determination on the lunar surface is available by visible light spectrometer, γ/X-ray spectrometer etc, the evaluations on the total reserves of 3He and ilmenite in the lunar deep and on the thickness of the lunar soil are still impossible so far. In this paper, the authors first give a rough analysis of the microwave brightness temperature images of the lunar disc observed using the NRAO 12 Meter Telescope and Siberian Solar Radio Telescope; then introduce our researches on the microwave dielectric properties of lunar soil simulators; finally, discuss some basic relations between the microwave brightness temperature and lunar soil properties.

  18. Microwave brightness temperature imaging and dielectric properties of lunar soil

    Indian Academy of Sciences (India)

    Wu Ji; Li Dihui; Zhang Xiaohui; Jiang Jingshan; A T Altyntsev; B I Lubyshev

    2005-12-01

    Among many scientific objectives of lunar exploration, investigations on lunar soil become attractive due to the existence of He3 and ilmenite in the lunar soil and their possible utilization as nuclear fuel for power generation.Although the composition of the lunar surface soil can be determined by optical and /X-ray spectrometers, etc., the evaluation of the total reserves of He3 and ilmenite within the regolith and in the lunar interior are still not available.In this paper,we give a rough analysis of the microwave brightness temperature images of the lunar disc observed using the NRAO 12 meter Telescope and Siberian Solar Radio Telescope.We also present the results of the microwave dielectric properties of terrestrial analogues of lunar soil and,discuss some basic relations between the microwave brightness temperature and lunar soil properties.

  19. Effects of "natural" water and "added" water on prediction of moisture content and bulk density of shelled corn from microwave dielectric properties.

    Science.gov (United States)

    Trabelsi, Samir; Nelson, Stuart O; Lewis, Micah A

    2010-01-01

    Dielectric properties of samples of shelled corn of "natural" water content and those prepared by adding water were measured in free space at microwave frequencies and 23 degrees C. Results of measurements of attenuation, phase shift and dielectric constant and loss factor at 9 GHz show no difference between the samples with "natural" water and those in which water was added artificially. Bulk densities and moisture contents predicted from calibration equations expressed in terms of dielectric properties of both natural and added water samples agreed closely, and standard errors were less than 1% for moisture content and relative error for bulk density was less than 5%.

  20. Three-dimensional all-dielectric metamaterial solid immersion lens for subwavelength imaging at visible frequencies

    Science.gov (United States)

    Fan, Wen; Yan, Bing; Wang, Zengbo; Wu, Limin

    2016-01-01

    Although all-dielectric metamaterials offer a low-loss alternative to current metal-based metamaterials to manipulate light at the nanoscale and may have important applications, very few have been reported to date owing to the current nanofabrication technologies. We develop a new “nano–solid-fluid assembly” method using 15-nm TiO2 nanoparticles as building blocks to fabricate the first three-dimensional (3D) all-dielectric metamaterial at visible frequencies. Because of its optical transparency, high refractive index, and deep-subwavelength structures, this 3D all-dielectric metamaterial-based solid immersion lens (mSIL) can produce a sharp image with a super-resolution of at least 45 nm under a white-light optical microscope, significantly exceeding the classical diffraction limit and previous near-field imaging techniques. Theoretical analysis reveals that electric field enhancement can be formed between contacting TiO2 nanoparticles, which causes effective confinement and propagation of visible light at the deep-subwavelength scale. This endows the mSIL with unusual abilities to illuminate object surfaces with large-area nanoscale near-field evanescent spots and to collect and convert the evanescent information into propagating waves. Our all-dielectric metamaterial design strategy demonstrates the potential to develop low-loss nanophotonic devices at visible frequencies. PMID:27536727

  1. Effect of Frequency on Emission of XeIast Excimer in a Pulsed Dielectric Barrier Discharge

    Science.gov (United States)

    Ou, Qiong-Rong; Meng, Yue-Dong; Xu, Xu; Shu, Xing-Sheng; Ren, Zhao-Xing

    2004-07-01

    Emission spectra of XeIast excimers and ultraviolet intensity at 253 nm from a dielectric barrier discharge (DBD) lamp excited by a pulsed voltage were measured as functions of pressure, electrical power, and frequency. In the DBD lamp driven by a higher frequency voltage, a more intense emission of XeIast excimers with high efficiency at 253 nm was found. A diffuse discharge mode was observed at high xenon pressure (>1 atm) with an excessive iodine concentration in the DBD driven by a high frequency (60 kHz) voltage.

  2. Effect of Frequency on Emission of XeI* Excimer in a Pulsed Dielectric Barrier Discharge

    Institute of Scientific and Technical Information of China (English)

    OU Qiong-Rong; MENG Yue-Dong; XU Xu; SHU Xing-Sheng; REN Zhao-Xing

    2004-01-01

    Emission spectra of XeI* excimers and ultraviolet intensity at 253 nm from a dielectric barrier discharge (DBD)lamp excited by a pulsed voltage were measured as functions of pressure, electrical power, and frequency. In the DBD lamp driven by a higher frequency voltage, a more intense emission of XeI* excimers with high efficiency at 253 nm was found. A diffuse discharge mode was observed at high xenon pressure (> 1 atm) with an excessive iodine concentration in the DBD driven by a high frequency (60 kHz) voltage.

  3. On structural, optical and dielectric properties of zinc aluminate nanoparticles

    Indian Academy of Sciences (India)

    E Muhammad Abdul Jamal; D Sakthi Kumar; M R Anantharaman

    2011-04-01

    Zinc aluminate nanoparticles with average particle size of 40 nm were synthesized using a sol–gel combustion method. X-ray diffractometry result was analysed by Rietveld refinement method to establish the phase purity of the material. Different stages of phase formation of the material during the synthesis were investigated using differential scanning calorimetry and differential thermogravimetric analysis. Particle size was determined with transmission electron microscopy and the optical bandgap of the nanoparticles was determined by absorption spectroscopy in the ultraviolet-visible range. Dielectric permittivity and a.c. conductivity of the material were measured for frequencies from 100 kHz to 8 MHz in the temperature range of 30–120°C. The presence of Maxwell–Wagner type interfacial polarization was found to exist in the material and hopping of electron by means of quantum mechanical tunneling is attributed as the reason for the observed a.c. conductivity.

  4. Synthesis, structural, dielectric and magnetic properties of polyol assisted copper ferrite nano particles

    Science.gov (United States)

    Pavithradevi, S.; Suriyanarayanan, N.; Boobalan, T.

    2017-03-01

    Nanocrystalline copper ferrite CuFe2O4 is synthesized by co-precipitation method in ethylene glycol as chelating agent, using sodium Hydroxide as precipitator at pH 8. The as synthesized CuFe2O4 is annealed at temperatures of 350 °C, 700 °C, and 1050 °C for 2 h respectively. The thermal analysis of the synthesized sample is done by TG technique. It is shown that at 260 °C ethylene glycol has evaporated completely and after 715 °C, spinel ferrite is formed with a cubic structure. The calculated lattice parameters are in agreement with the reported values. FTIR spectra of CuFe2O4 nano particles are as synthesized and annealed at 1050 °C and recorded between 400 cm-1 and 4000 cm-1. It shows that when the temperature increases ethylene glycol gradually evaporates. Finally, nano crystalline single phase spinel ferrite is obtained. X-ray diffraction (XRD) and electron diffraction (EDS) studies show that the sample is indexed as the face centered cubic spinel structure. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicated that the particles are flaky and spherical with the crystallite size in the range of 25-34 nm. From the dielectric studies, the dielectric constant decreases as the frequency increases. Low value of dielectric loss at higher frequencies suggests that the material is suitable for high frequency applications. AC conductivity increases with frequency. The magnetic properties of the samples are measured using a vibrating sample magnetometer (VSM) at room temperature, which shows that the sample exhibited a typical super paramagnetic behavior at low temperature. The saturation magnetization, remanant magnetism, and coercivity increases with applied field.

  5. Inkjet-printed thin film radio-frequency capacitors based on sol-gel derived alumina dielectric ink

    KAUST Repository

    McKerricher, Garret

    2017-05-03

    There has been significant interest in printing radio frequency passives, however the dissipation factor of printed dielectric materials has limited the quality factor achievable. Al2O3 is one of the best and widely implemented dielectrics for RF passive electronics. The ability to spatially pattern high quality Al2O3 thin films using, for example, inkjet printing would tremendously simplify the incumbent fabrication processes – significantly reducing cost and allowing for the development of large area electronics. To-date, particle based Al2O3 inks have been explored as dielectrics, although several drawbacks including nozzle clogging and grain boundary formation in the films hinder progress. In this work, a particle free Al2O3 ink is developed and demonstrated in RF capacitors. Fluid and jetting properties are explored, along with control of ink spreading and coffee ring suppression. The liquid ink is heated to 400 °C decomposing to smooth Al2O3 films ~120 nm thick, with roughness of <2 nm. Metal-insulator-metal capacitors, show high capacitance density >450 pF/mm2, and quality factors of ~200. The devices have high break down voltages, >25 V, with extremely low leakage currents, <2×10−9 A/cm2 at 1 MV/cm. The capacitors compare well with similar Al2O3 devices fabricated by atomic layer deposition.

  6. Dielectric properties of periodic heterostructures: A computational electrostatics approach

    Science.gov (United States)

    Brosseau, C.; Beroual, A.

    1999-04-01

    The dielectric properties of heterogeneous materials for various condensed-matter systems are important for several technologies, e.g. impregnated polymers for high-density capacitors, polymer carbon black mixtures for automotive tires and current limiters in circuit protection. These multiscale systems lead to challenging problems of connecting microstructural features (shape, spatial arrangement and size distribution of inclusions) to macroscopic materials response (permittivity, conductivity). In this paper, we briefly discuss an ab initio computational electrostatics approach, based either on the use of the field calculation package FLUX3D (or FLUX2D) and a conventional finite elements method, or the use of the field calculation package PHI3D and the resolution of boundary integral equations, for calculating the effective permittivity of two-component dielectric heterostructures. Numerical results concerning inclusions of permittivity \\varepsilon_1 with various geometrical shapes periodically arranged in a host matrix of permittivity \\varepsilon_2 are provided. Next we discuss these results in terms of phenomenological mixing laws, analytical theory and connectedness. During the pursuit of these activities, several interesting phenomena were discovered that will stimulate further investigation.

  7. TECHNICAL NOTE: Dielectric and piezoelectric properties of piezoelectric ceramic sulphoaluminate cement composites

    Science.gov (United States)

    Cheng, Xin; Huang, Shifeng; Chang, Jun; Lu, Lingchao; Liu, Futian; Ye, Zengmao; Wang, Shoude

    2005-10-01

    Using cement as the matrix of piezoelectric smart composites can solve the problem of mismatch of smart composites and concrete structure in civil engineering. 0 3 cement based piezoelectric composites were fabricated by a compression technique using PMN and sulphoaluminate cement as raw materials. The influence of the PMN content on the dielectric and piezoelectric properties of the composites was investigated. The temperature dependence of the dielectric properties of the composites was discussed in detail. The results indicate that the dielectric constants are almost constant in the temperature range from -30 to 50 °C, which shows excellent dielectric temperature stability. With increasing PMN content, the piezoelectric and dielectric properties of the composites increase. The theoretical values of the dielectric constants show good agreement with the experimental values for the composites.

  8. The effect of different electrode structures on the dielectric properties of lanthanum-doped lead titanate ferroelectric thin films

    Institute of Scientific and Technical Information of China (English)

    LIU Hong; PU Zhaohui; ZHU Xiaohong; XIAO Dingquan; ZHU Jianguo

    2007-01-01

    Lanthanum-doped lead titanate[(Pb0.9,La0.1)TiO3,PLT10]ferroelectric thin films were grown on Si(100)and Pt/Ti/SiO2/Si(100)substrates by radio frequency(RF)magnetron sputtering.The crystalline properties of PLT10 films were studied by X-ray diffractometry(XRD).Photolithographic technique was applied to fabricate the interdigital electrodes on PLT10 thin films on Si(100)substrates.The dielectric properties of PLT10 thin films with different electrodes were measured.At room temperature and 1 kHz testing frequency,the dielectric constant of the PLT10 min film with interdigital electrodes is 386.ThC dielectric constant of the PLT10 thin film fabricated under the same technological conditions with parallel plate electrodes structure is 365,while the dielectric constant and loss of the PLT10 thin film with interdigital electrodes are decreased faster than those of the film with parallel plate electrodes with increasing frequency.This is because more influences of interface state are introduced due to the interdigital electrode configuration.

  9. Effects of Dielectric Substrates and Ground Planes on Resonance Frequency of Archimedean Spirals.

    Science.gov (United States)

    Hooker, Jerris W; Ramaswamy, Vijaykumar; Arora, Rajendra K; Edison, Arthur S; Brey, William W

    2016-04-01

    Superconducting self-resonant spiral structures are of current interest for applications both in metamaterials and as probe coils for nuclear magnetic resonance (NMR) spectroscopy for high-sensitivity chemical analysis. Accurate spiral models are available in the literature for behavior of a spiral below and up to self-resonance. However, knowledge of the higher modes is also important. We present the relationships between the spiral parameters and the multiple mode frequencies of single sided spirals on dielectric substrates as modeled by method of moments simulation. In the absence of a ground plane, we find that the mode frequency has a linear though not necessarily harmonic dependence on the mode number. The effect of a thick substrate can be approximated by an effective dielectric constant. But when the thickness is less than 20% of the spiral trace width (router - rinner) this approximation is no longer accurate. We have developed a simple empirical formula to predict the higher modes.

  10. High-frequency dielectric and magnetic anomaly at the phase transition in NaV2O5

    NARCIS (Netherlands)

    Smirnov, A.I.; Popova, M.N.; Sushkov, A.B.; Golubchik, S.A.; Khomskii, D.I.; Mostovoy, M.V.; Vasil’ev, A.N.; Isobe, M.; Ueda, Y.

    1999-01-01

    We found anomalies in the temperature dependence of the dielectric and magnetic susceptibility of NaV2O5 in the microwave and far-infrared frequency ranges. The anomalies occur at the phase transition temperature Tc, at which the spin gap opens. The real parts of the dielectric constants εa and εc

  11. Zirconium titanate thin film prepared by surface sol-gel process and effects of thickness on dielectric property

    CERN Document Server

    Kim, C H

    2002-01-01

    Single phase of multicomponent oxide ZrTiO sub 4 film could be prepared through surface sol-gel route simply by coating the mixture of 100mM zirconium butoxide and titanium butoxide on Pt/Ti/SiO sub 2 /Si(100) substrate, following pyrolysis at 450 .deg. C, and annealing it at 770 .deg. C. The dielectric constant of the film was reduced as the film thickness decreased due to of the interfacial effects caused by layer/electrode and a few voids inside the multilayer. However, the dielectric property was independent of applied dc bias sweeps voltage (-2 to +2 V). The dielectric constant of bulk film, 31.9, estimated using series-connected capacitor model was independent of film thickness and frequency in the measurement range, but theoretical interfacial thickness, t sub i , was dependent on the frequency. It reached a saturated t sub i value, 6.9 A, at high frequency by extraction of some capacitance component formed at low frequency range. The dielectric constant of bulk ZrTiO sub 4 pellet-shaped material was 3...

  12. Synthesized High-Frequency Thyristor for Dielectric Barrier Discharge Excimer Lamps

    OpenAIRE

    2012-01-01

    International audience; Dielectric barrier discharge (DBD) lamps, being capacitive loads, must be associated with bidirectional current sources for an appropriate control of the transferred power. Pulsed current source supplies, which are known to offer very interesting performances, require specific power switches that are able to manage bidirectional voltage and unidirectional current at much higher frequencies (several hundreds of kilohertz) than commercial thyristors. This paper proposes t...

  13. Dielectric and Pyroelectric Properties of La- and Pr-Modified Tungsten-Bronze Ferroelectrics

    Science.gov (United States)

    Parida, B. N.; Das, Piyush R.; Padhee, R.; Choudhary, R. N. P.

    2013-08-01

    The polycrystalline materials Li2Pb2R2W2Ti4Nb4O30 (R = La, Pr) of the tungsten-bronze structural family have been synthesized using a high- temperature mixed-oxide method. Room-temperature x-ray diffraction (XRD) analysis confirms the formation of single-phase compounds. Room-temperature scanning electron micrography of the pellet samples shows a uniform distribution of well-defined different sizes of grains on the surface of the samples, confirming the formation of single-phase compounds. Study of the frequency and temperature dependence of the dielectric constant and loss tangent suggests the existence of dielectric dispersion in the materials. The ferroelectric phase transition in the samples has been studied based on the variation of fitting parameters (calculated from a theoretical model) with temperature. Studies of pyroelectric properties [figure of merit (FOM) and coefficient] show that the materials have reasonably high FOM useful for pyroelectric detectors. The variation of alternating-current (AC) and direct-current (DC) conductivity with inverse absolute temperature (obtained from dielectric data) follows a typical Arrhenius relation. The low leakage current and negative temperature coefficient of resistance behavior of the samples have been verified from J- E plots.

  14. Lithium-doped hydroxyapatite nano-composites: Synthesis, characterization, gamma attenuation coefficient and dielectric properties

    Science.gov (United States)

    Badran, H.; Yahia, I. S.; Hamdy, Mohamed S.; Awwad, N. S.

    2017-01-01

    Lithium-hydroxyapatite (0, 1, 5, 10, 20, 30 and 40 wt% Li-HAp) nano-composites were synthesized by sol-gel technique followed by microwave-hydrothermal treatment. The composites were characterized by X-ray diffraction (XRD), Field emission scanning electron microscope (FE-SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) and Raman techniques. Gamma attenuation coefficient and the dielectric properties for all composites were investigated. The crystallinity degree of Li-doped HAp was higher than that of un-doped HAp. Gamma attenuation coefficient values increased from 0.562 cm-1 for 0 wt% Li-HAp to 2.190 cm-1 for 40 wt% Li-HAp. The alternating current conductivity increased with increasing frequency. The concentration of Li affect the values of dielectric constant where Li doped HAp of low dielectric constant can have an advantage for healing in bone fractures. The calcium to phosphorus ratio decreased from 1.43 to 1.37 with the addition of lithium indicating the Ca deficiency in the studied composites. Our findings lead to the conclusion that Li-HAp is a new nano-composite useful for medical applications and could be doped with gamma shield materials.

  15. DIELECTRIC AND PYROELECTRIC PROPERTIES OF THE COMPOSITES OF FERROELECTRIC CERAMIC AND POLY(VINYL CHLORIDE

    Directory of Open Access Journals (Sweden)

    M.Olszowy

    2003-01-01

    Full Text Available The dielectric and pyroelectric properties of lead zirconate titanate/poly(vinyl chloride [PZT/PVC] and barium titanate/poly(vinyl chloride [BaTiO3/ PVC] composites were studied. Flexible composites were fabricated in the thin films form (200-400 μm by hot-pressed method. Powders of PZT or BaTiO3 in the shape of ≤ 75 μm ceramics particles were dispersed in a PVC matrix, providing composites with 0-3} connectivity. Distribution of the ceramic particles in the polymer phase was examined by scanning electron microscopy. The analysis of the thermally stimulated currents (TSC have also been done. The changes of dielectric and pyroelectric data on composites with different contents of ceramics up to 40% volume were investigated. The dielectric constants were measured in the frequency range from 600 Hz to 6 MHz at room temperature. The pyroelectric coefficient for BaTiO3/PVC composite at 343 K is about 35 μC/m2K which is higher than that of β-PVDF (10 μC/m2 K.

  16. Influence of Water on the Structure and Dielectric Properties of the Microcrystalline and Nano-Cellulose

    Science.gov (United States)

    Kovalov, Kostiantyn M.; Alekseev, Olexander M.; Lazarenko, Maxim M.; Zabashta, Yu F.; Grabovskii, Yurii E.; Tkachov, Sergii Yu

    2017-07-01

    Influence of water in the different states on a structure and dielectric properties of microcrystalline cellulose were studied by of X-ray, thermogravimetry, and dielectric spectroscopy. At research of microcrystalline cellulose (MCC) with different content of water, it is shown that the molecules of water are located in the macropores of MCC and in multimolecular hydrated layers. It is shown that at the increase of concentration of water in a hydrated shell, the reorganization of molecules of cellulose in the surface of crystallites takes place, and as a result, their transversal size and crystallinity increase. It is shown that during the concentration of water, more than 13% in a continuous hydrated shell of crystallites appears. Temperature dependences of actual and imaginary parts of complex dielectric permittivity were studied in the interval of temperatures [-180 ÷ 120] °C on frequencies of f = 5, 10, 20, and 50 kHz. A low-temperature relaxation process and high-temperature transition were observed. Low-temperature relaxation process which is related to transition of surface methylol groups of molecules of cellulose conformation from tg to tt is shifted toward low temperatures at the increase of concentration of water in microcrystalline cellulose.

  17. Electric and dielectric properties of some gamma-irradiated cabal glasses

    Science.gov (United States)

    El-Batal, H. A.; Farouk, H.; Ezz-Eldin, F. M.

    1996-06-01

    Electrical conductivity and dielectric properties have been studied for the glass system CaOB 2O 3Al 2O 3 in the temperature range 40-200°C. The substitution of 5% B 2O 3 by CaO or replacing 5% CaO by Na 2O or MgO cause a decrease in the conductivity, but the decrease obtained by soda is greater than that of magnesia. The activation energies of the tested glasses were calculated. All the glasses investigated showed a dielectric constant almost independent of temperature at fixed frequency. The effect of subjecting the glass to a constant dose of gamma-rays changes both the electrical conductivity and dielectric constant. The experimental results were discussed in relation to the specific conduction mechanism in such glasses. Also the effect of varying glass composition or temperature on the mobility or migration of current carrier was considered. The possible creation of induced defects in glass on irradiation was evaluated.

  18. Apparatus and method to measure dielectric properties (epsilon(') and epsilon(")) of ionic liquids.

    Science.gov (United States)

    Göllei, Attila; Vass, András; Pallai, Elisabeth; Gerzson, Miklós; Ludányi, Lajos; Mink, János

    2009-04-01

    Conventional techniques for measurement of dielectric properties of ionic liquids or electrolyte solutions fail because the samples are largely short circuited by the high electrical conductance. The object of the author's research activity was to elaborate an apparatus (microwave dielectrometer) and method suitable to measure the dielectric constant (epsilon(')) and loss factor (epsilon(")) of well conducting ionic liquids and other solvents. This process is based on a revised waveguide method completed with an automatic calibration possibility. Contrary to conventional measuring methods this technique uses about 20 W/g power density. The measurements were carried out at 2.45 GHz frequency in the temperature range from 10 up to 100 degrees C. The obtained (epsilon(')) and (epsilon(")) values of different solvents were compared with several published (calculated and measured) data. Statistical analysis was used to determine the error of measurements and distilled water was chosen as a standard for study of data dispersion. To accomplish statistical analysis, namely, the dielectric characteristics have to be determined at the same temperature. The values of variances were less or equal 1 in case of epsilon(') and decrease with increasing temperature. In case of epsilon(") the variance data were much smaller.

  19. Structural, Microhardness, Photoconductivity, and Dielectric Properties of Tris(thiourea Cadmium Sulphate Single Crystals

    Directory of Open Access Journals (Sweden)

    A. P. Arthi

    2014-01-01

    Full Text Available Semiorganic nonlinear optical tris(thiourea cadmium sulphate (TTCS single crystals were grown by slow evaporation method. The crystal system, cell parameter of the grown crystal, was identified by powder X-ray diffraction study. The self-focusing Z-scan technique has been employed to observe the third-order nonlinear optical property of the grown crystal. The mechanical property of the grown crystal was examined by using Vicker’s microhardness test. Chemical etching studies were made on the TTCS crystal using water as an etchant. The dark current and photocurrent properties of the crystal were estimated by using photoconductivity study. The dielectric constant of grown crystal was studied in different temperature by varying applied frequencies.

  20. Characterization of dielectric materials

    Energy Technology Data Exchange (ETDEWEB)

    King, Danny J.; Babinec, Susan; Hagans, Patrick L.; Maxey, Lonnie C.; Payzant, Edward A.; Daniel, Claus; Sabau, Adrian S.; Dinwiddie, Ralph B.; Armstrong, Beth L.; Howe, Jane Y.; Wood, III, David L.; Nembhard, Nicole S.

    2017-06-27

    A system and a method for characterizing a dielectric material are provided. The system and method generally include applying an excitation signal to electrodes on opposing sides of the dielectric material to evaluate a property of the dielectric material. The method can further include measuring the capacitive impedance across the dielectric material, and determining a variation in the capacitive impedance with respect to either or both of a time domain and a frequency domain. The measured property can include pore size and surface imperfections. The method can still further include modifying a processing parameter as the dielectric material is formed in response to the detected variations in the capacitive impedance, which can correspond to a non-uniformity in the dielectric material.

  1. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    Science.gov (United States)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2016-10-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' } ) and imaginary (ɛ ^' ' } ) parts of the complex permittivity (ɛ ^* ) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  2. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    Science.gov (United States)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2017-02-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the complex permittivity (ɛ ^*) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  3. Structural and dielectric properties of doped ferrite nanomaterials suitable for microwave and biomedical applications

    Directory of Open Access Journals (Sweden)

    Imran Sadiq

    2015-10-01

    Full Text Available The sol–gel auto-combustion method was adopted to synthesize nanomaterials of single-phase X-type hexagonal ferrites with the composition of Sr2−xGdxNi2Fe28−yCdyO46 (x=0.00, 0.02, 0.04, 0.06, 0.08, 0.10 and y=0, 0.1, 0.2, 0.3, 0.4, 0.5. The structural properties were carried out by XRD analysis and the lattice parameters show variation with the doping of Gd–Cd. The average particle size measured by TEM was in the range of 8–10 nm which is beneficial in obtaining suitable signal-to-noise ratio in recording media and biomedical applications. The room temperature resistivity enhanced with the increase of the dopant concentration. The increase in resistivity indicates that the synthesized materials can be considered good for the formation of the multilayer chip inductors (MLCIs as well as for the reduction of eddy current losses. The dielectric constant decreased with the increase in the frequency which is the general reported trend of the hexagonal ferrites and can be explained on the basis of Koop׳s theory and Maxwell–Wagner polarization-model. The abnormal dielectric behavior indicates the formation of small polarons in the material. The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices (MF.

  4. Dielectric properties of betaine phosphite and deuterated betaine phosphite films

    Science.gov (United States)

    Balashova, E. V.; Krichevtsov, B. B.; Zaitseva, N. V.; Pankova, G. A.; Frederiks, I. D.; Lemanov, V. V.

    2011-01-01

    Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO3, α-SiO2, α-Al2O3, and NdGaO3 substrates. These films consist of large single-crystal blocks in which the polar axis ( b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T c is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T c: from T c = 200 K for BPI-based structures to T c = 280 K for structures with a high degree of deuteration ( d ˜ 90%).

  5. Characterization of surface dielectric barrier discharge influenced by intermediate frequency for ozone production

    Science.gov (United States)

    Abdelaziz, Ayman A.; Ishijima, Tatsuo; Seto, Takafumi; Osawa, Naoki; Wedaa, Hassan; Otani, Yoshio

    2016-06-01

    The aim of this study is to investigate the effect of the intermediate frequency (1-10 kHz) of the sinusoidal driving voltage on the characteristics of a developed surface dielectric barrier discharge (SDBD)-based reactor having spikes on its discharge electrode. Moreover, its influence on the production of ozone and nitrogen oxide byproducts is evaluated. The results show that SDBD is operated in the filamentary mode at all the frequencies. Nevertheless, the pulses of the discharge current at high frequencies are much denser and have higher amplitudes than those at low frequencies. The analysis of the power consumed in the reactor shows that a small portion of the input power is dissipated in the dielectric material of SDBD source, whereas the major part of the power is consumed in the plasma discharge. The results of the ozone production show that higher frequencies have a slightly adverse effect on the ozone production at relatively high energy density values, where the ozone concentration is slightly decreased when the frequency is increased at the same energy density. The temperature of the discharge channels and gas is not a crucial factor for the decomposition of ozone in this reactor, while the results of the measurements of nitrogen oxides characteristics indicate that the formation of NO and NO2 has a significant adverse effect on the production efficiency of ozone due to their oxidation to another nitrogen oxides and their catalytic effect.

  6. Dielectric Properties of Collagen on Plasma Modified Polyvinylidene Fluoride

    Directory of Open Access Journals (Sweden)

    R. M. Dahan

    2012-01-01

    Full Text Available Problem statement: The attachment of biopolymers such as collagen on inert polymeric template created great challenge due to hydrophobic nature of polymeric material. The modification of PVDF for improved adhesion and introduction of specific functionalities have been widely recognized in various industrial applications. Typical methods for modifying polymer surface such as chemical etching and UV irradiation are not favorable as it requires high temperature and the use of chemical solvents. However plasma modification is suitable as it utilizes low heat and a clean environment, thus preventing contamination on the deposited collagen. Approach: Free standing orientated Poly (Vinylidene Fluoride (PVDF films were fabricated by solution casting method and dried in a convention oven. The dried PVDF films were orientated in a tensile machine at temperature 70°C enclosed in a custom made environmental chamber. The pulling rates of 5 mm min-1 were utilized with a draw ratio of 2 (R = Lfinal/Linitial. The PVDF film was plasma treated for 60 sec to enhance the hydrophilic property of PVDF and utilized as template for collagen deposition. The deposited collagen on surface of PVDF was left in desiccators at temperature of 24°C for complete drying. Results: The untreated and plasma-treated PVDF template were observed for water contact angle measurement, the functional group and dielectric properties of collagen were observed and measured by FTIR and SOLARTRON respectively. Conclusion: The orientated PVDF films were produced at pulling speed of 5 mm min-1 and temperature of 70°C. The hydrophobic PVDF surface was transformed to a hydrophilic surface by plasma treatment for collagen deposition. The FTIR result shows the overlapping peaks of C-H and C-F in range 1500-1000 cm-1 which indicates the C-C bonding of collagen and PVDF. The significant increase in dielectric constant is a result from the favorable bonding between collagen and PVDF template.

  7. Effects of magnetic field treatment on dielectric properties of CCTO@Ni/PVDF composite with low concentration of ceramic fillers

    Energy Technology Data Exchange (ETDEWEB)

    Chi, Q. G., E-mail: qgchi@hotmail.com, E-mail: empty-cy@l63.com [Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080 (China); State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an 710049 (China); Gao, L. [Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080 (China); College of Electrical Engineering, Suihua University, Suihua 152061 (China); Wang, X.; Chen, Y., E-mail: qgchi@hotmail.com, E-mail: empty-cy@l63.com; Dong, J. F.; Cui, Y.; Lei, Q. Q. [Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080 (China)

    2015-11-15

    Using melt mixing, we produced a ceramic/polymer composite with a matrix of polyvinylidene fluoride (PVDF) and a filler of 5 vol.% Ni-deposited CaCu{sub 3}Ti{sub 4}O{sub 12} core-shell ceramic particles (CCTO@Ni), and studied its prominent dielectric characteristics for the first. Its phase composition and morphology were analyzed by X-ray diffraction and scanning electron microscopy, respectively. After treating the composite films with various durations of a magnetic field treatment, we compared their dielectric properties. We found that the CCTO@Ni ceramic had a typical urchin-like core-shell structure, and that different durations of the magnetic field treatment produced different distributions of ceramic particles in the PVDF matrix. The dielectric permittivity of the untreated CCTO@Ni/PVDF composite was 20% higher than that of neat PVDF, and it had a low loss tangent. However, only the composite treated for 30 min in the magnetic field had an ultra-high dielectric permittivity of 1.41 × 10{sup 4} at 10 Hz, three orders of magnitude higher than the untreated composite, which declined dramatically with increasing frequency, accompanied by an insulating-conducting phase transition and an increase in loss tangent. Our results demonstrate that changes in the dielectric properties of PVDF composites with magnetic field treatment are closely related to the percolation effect and interfacial polarization.

  8. Effects of magnetic field treatment on dielectric properties of CCTO@Ni/PVDF composite with low concentration of ceramic fillers

    Directory of Open Access Journals (Sweden)

    Q. G. Chi

    2015-11-01

    Full Text Available Using melt mixing, we produced a ceramic/polymer composite with a matrix of polyvinylidene fluoride (PVDF and a filler of 5 vol.% Ni-deposited CaCu3Ti4O12 core-shell ceramic particles (CCTO@Ni, and studied its prominent dielectric characteristics for the first. Its phase composition and morphology were analyzed by X-ray diffraction and scanning electron microscopy, respectively. After treating the composite films with various durations of a magnetic field treatment, we compared their dielectric properties. We found that the CCTO@Ni ceramic had a typical urchin-like core-shell structure, and that different durations of the magnetic field treatment produced different distributions of ceramic particles in the PVDF matrix. The dielectric permittivity of the untreated CCTO@Ni/PVDF composite was 20% higher than that of neat PVDF, and it had a low loss tangent. However, only the composite treated for 30 min in the magnetic field had an ultra-high dielectric permittivity of 1.41 × 104 at 10 Hz, three orders of magnitude higher than the untreated composite, which declined dramatically with increasing frequency, accompanied by an insulating-conducting phase transition and an increase in loss tangent. Our results demonstrate that changes in the dielectric properties of PVDF composites with magnetic field treatment are closely related to the percolation effect and interfacial polarization.

  9. Dielectric permittivity tensor and low frequency instabilities of a magnetoactive current-driven plasma with nonextensive distribution

    Energy Technology Data Exchange (ETDEWEB)

    Niknam, A. R., E-mail: a-niknam@sbu.ac.ir [Laser and Plasma Research Institute, Shahid Beheshti University, G.C., Tehran (Iran, Islamic Republic of); Rastbood, E.; Khorashadizadeh, S. M. [Physics Department, University of Birjand, Birjand (Iran, Islamic Republic of)

    2015-12-15

    The dielectric permittivity tensor of a magnetoactive current-driven plasma is obtained by employing the kinetic theory based on the Vlasov equation and Lorentz transformation formulas with an emphasize on the q-nonextensive statistics. By deriving the q-generalized dispersion relation of the low frequency modes in this plasma system, the possibility and properties of filamentation and ion acoustic instabilities are then studied. It is shown that the occurrence and the growth rate of these instabilities depend strongly on the nonextensive parameters, external magnetic field strength, and drift velocity. It is observed that the growth rate of ion acoustic instability is affected by the magnetic field strength much more than that of the filamentation instability in the low frequency range. The external magnetic field facilitates the development of the ion-acoustic instability. It is also shown that the filamentation is the dominant instability only for the high value of drift velocity.

  10. Structural, dielectric and magnetic properties of Gd substituted manganese ferrite nanoparticles

    Science.gov (United States)

    Murugesan, C.; Sathyamoorthy, B.; Chandrasekaran, G.

    2015-08-01

    Gd3+ ion-substituted manganese ferrite nanoparticles with the chemical formula MnGdxFe2-xO4 (x = 0.0, 0.05, and 0.1) were synthesized by sol-gel auto combustion method. Thermal stability of the as-prepared sample was analyzed using thermo gravimetric and differential thermal analysis (TG-DTA) and the result reveals that the prepared sample is thermally stable above 300 °C. Structural and morphology studies were performed using powder x-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). Indexed PXRD patterns confirm the formation of pure cubic spinel structure. The average crystallite sizes calculated using Sherrer’s formula decreased from 47 nm to 32 nm and lattice constant was enhanced from 8.407 Å to 8.432 Å. The FTIR spectrum of manganese ferrite shows a high frequency vibrational band at 564 cm-1 assigned to tetrahedral site and a low frequency vibrational band at 450 cm-1 assigned to octahedral site which are shifted to 556 cm-1 and 439 cm-1 for Gd3+ substitution and confirm the incorporation of Gd3+ into manganese ferrite. SEM analysis shows the presence of agglomerated spherical shaped particles at the surface. Room temperature dielectric and magnetic properties were studied using broadband dielectric spectroscopy (BDS) and vibrating sample magnetometry (VSM). Frequency dependent dielectric constant, ac conductivity and tan delta were found to increase with Gd3+ ion substitution. The measured values of saturation magnetization decrease from 46.6 emu g-1 to 41 emu g-1 with increase in Gd3+ concentration and coercivity decreases from 179.5 Oe to 143 Oe.

  11. Core-shell structured polystyrene/BaTiO3 hybrid nanodielectrics prepared by in situ RAFT polymerization: a route to high dielectric constant and low loss materials with weak frequency dependence.

    Science.gov (United States)

    Yang, Ke; Huang, Xingyi; Xie, Liyuan; Wu, Chao; Jiang, Pingkai; Tanaka, Toshikatsu

    2012-11-23

    A novel route to prepare core-shell structured nanocomposites with excellent dielectric performance is reported. This approach involves the grafting of polystyrene (PS) from the surface of BaTiO(3) by an in situ RAFT polymerization. The core-shell structured PS/BaTiO(3) nanocomposites not only show significantly increased dielectric constant and very low dielectric loss, but also have a weak frequency dependence of dielectric properties over a wide range of frequencies. In addition, the dielectric constant of the nanocomposites can also be easily tuned by varying the thickness of the PS shell. Our method is very promising for preparing high-performance nanocomposites used in energy-storage devices.

  12. Atomic-scale microstructures, Raman spectra and dielectric properties of cubic pyrochlore-typed Bi1.5MgNb1.5O7 dielectric ceramics

    KAUST Repository

    Li, Yangyang

    2014-07-01

    Single-phase cubic pyrochlore-typed Bi1.5MgNb 1.5O7 (BMN) dielectric ceramics were synthesized at temperatures of 1050-1200 °C by solid-state reaction method. Their atomic-scale microstructures and dielectric properties were investigated. X-ray diffraction patterns revealed that the BMN ceramics had an average cubic pyrochlore structure, whereas the Raman spectra indicated that they had an essentially cubic symmetry with small local deviations at the A and O\\' sites of the cubic pyrochlore structure. This was confirmed by selected electron area diffraction (SAED) patterns, where the reflections of {442} (not allowed in the cubic pyrochlore with Fd3̄m symmetry) were clearly observed. SEM and TEM images revealed that the average grain size was increased with the sintering temperature, and an un-homogeneous grain growth was observed at high temperatures. HRTEM images and SAED patterns revealed the single-crystalline nature of the BMN ceramic grains. Energy dispersive spectroscopy (EDS) elemental mapping studies indicated that the compositional distributions of Bi, Mg, Nb and O elements in the ceramic grains were homogenous, and no elemental precipitation was observed at the grain boundary. Quantitative EDS data on ceramic grains revealed the expected cationic stoichiometry based on the initial composition of Bi1.5MgNb1.5O7. Dielectric constants of all the BMN samples exhibited almost frequency independent characteristic in the frequency range of 102-106 Hz, and the highest value was 195 for the BMN ceramics sintered at sintered at 1150 °C with the highest bulk density. The dielectric losses were stable and less than 0.002 in the frequency range of 102-105 Hz. The high dielectric constants of the present BMN samples can be ascribed to the local atomic deviations at the A and O\\' sites from the ideal atomic positions of the pyrochlore structure, which affect the different polarization mechanisms in the BMN ceramics, and which in turn enhance the dielectric

  13. Quantitative property-structural relation modeling on polymeric dielectric materials

    Science.gov (United States)

    Wu, Ke

    Nowadays, polymeric materials have attracted more and more attention in dielectric applications. But searching for a material with desired properties is still largely based on trial and error. To facilitate the development of new polymeric materials, heuristic models built using the Quantitative Structure Property Relationships (QSPR) techniques can provide reliable "working solutions". In this thesis, the application of QSPR on polymeric materials is studied from two angles: descriptors and algorithms. A novel set of descriptors, called infinite chain descriptors (ICD), are developed to encode the chemical features of pure polymers. ICD is designed to eliminate the uncertainty of polymer conformations and inconsistency of molecular representation of polymers. Models for the dielectric constant, band gap, dielectric loss tangent and glass transition temperatures of organic polymers are built with high prediction accuracy. Two new algorithms, the physics-enlightened learning method (PELM) and multi-mechanism detection, are designed to deal with two typical challenges in material QSPR. PELM is a meta-algorithm that utilizes the classic physical theory as guidance to construct the candidate learning function. It shows better out-of-domain prediction accuracy compared to the classic machine learning algorithm (support vector machine). Multi-mechanism detection is built based on a cluster-weighted mixing model similar to a Gaussian mixture model. The idea is to separate the data into subsets where each subset can be modeled by a much simpler model. The case study on glass transition temperature shows that this method can provide better overall prediction accuracy even though less data is available for each subset model. In addition, the techniques developed in this work are also applied to polymer nanocomposites (PNC). PNC are new materials with outstanding dielectric properties. As a key factor in determining the dispersion state of nanoparticles in the polymer matrix

  14. Dielectric property determination of hybrid Al2O3-filled MWCNT buckypaper by the rectangular cavity perturbation technique

    Science.gov (United States)

    Miao, Hsin-Yuan; Liu, Jih-Hsin; Saravanan, L.; Tsao, Che-Wei; Pan, Jui-Wen

    2015-04-01

    This study investigated the complex dielectric permittivity of freestanding multiwalled carbon nanotube buckypaper (MWCNT-BP) and a synthesized hybrid alumina-filled buckypaper (Al2O3-BP) composite with different alumina loadings (5-30 wt%). The non-destructive microwave transmission technique for complex permittivity determination involving cavity perturbation was employed to characterize a set of Al2O3-BP sheets. This was done by filling a rectangular cavity resonator with a standard dielectric Teflon sample and then performing permittivity measurements for the buckypaper (BP) samples in the X-band frequency range (7-12 GHz). Field-emission scanning electron microscopy (FESEM) was used to analyze the morphology of the MWCNT-BP and the alumina-loaded BP composites. DC electrical resistivity measurements clearly demonstrated conductor-insulator transition. The effect of alumina loadings on the dielectric properties of the synthesized hybrid Al2O3-BP sheet is discussed.

  15. Structural characterization and dielectric properties of BaTiO3 thin films obtained by spin coating

    Directory of Open Access Journals (Sweden)

    Branimir Bajac

    2014-12-01

    Full Text Available Barium titanate thin films were prepared by spin coating deposition technique of an acetic precursor sol and sintered at 750, 900 and 1050 °C. Phase composition of the obtained thin films was characterized by X-ray diffraction and Raman spectroscopy. Their morphology was analysed by scanning electron microscopy and atomic force microscopy. Dielectric properties of thin films sintered at 750 and 900 °C were characterized by LCD device, where the influence of sintering temperature on dielectric permittivity and loss tangent was inspected. It was concluded that higher sintering temperature increases grain size and amount of tetragonal phase, hence higher relative permittivity was recorded. The almost constant relative permittivity in the measured frequency (800 Hz–0.5 MHz and temperature (25–200 °C ranges as well as low dielectric loss are very important for the application of BaTiO3 films in microelectronic devices.

  16. Dielectric properties of nanosilica/low-density polyethylene composites: The surface chemistry of nanoparticles and deep traps induced by nanoparticles

    Directory of Open Access Journals (Sweden)

    S. Ju

    2014-09-01

    Full Text Available Four kinds of nanosilica particles with different surface modification were employed to fabricate low-density polyethylene (LDPE composites using melt mixing and hot molding methods. The surface chemistry of modified nanosilica was analyzed by X-ray photoelectron spectroscopy. All silica nanoparticles were found to suppress the space charge injection and accumulation, increase the volume resistivity, decrease the permittivity and dielectric loss factor at low frequencies, and decrease the dielectric breakdown strength of the LDPE polymers. The modified nanoparticles, in general, showed better dielectric properties than the unmodified ones. It was found that the carrier mobility, calculated from J–V curves using the Mott-Gurney equation, was much lower for the nanocomposites than for the neat LDPE.

  17. Densification and dielectric properties of SrO–Al2O3–B2O3 ceramic bodies

    Indian Academy of Sciences (India)

    Doaa A Abdel Aziz; Shama E Ahmed

    2011-02-01

    The influence of SrO (0.0–5.0 wt%) on partial substitution of alpha alumina (corundum) in ceramic composition (95 Al2O3–5B2O3) have been studied by co-precipitated process and their phase composition, microstructure, microchemistry and microwave dielectric properties were studied. Phase composition was revealed by XRD, while microstructure andmicrochemistry were investigated by electron-probe microanalysis (EPMA). The dielectric properties by means of dielectric constant (r), quality factor ( × ) and temperature coefficient of resonant frequency (f) were measured in the microwave frequency region using a network analyser by the resonance method. The addition of B2O3 and SrO significantly reduced the sintering temperature of alumina ceramic bodies to 1600°C with optimum density (∼ 4 g/cm3) as compared with pure alumina powders recycled from Al dross (3.55 g/cm3 sintered at 1700°C). The sintered ceramic bodies show different ranges for the dielectric properties. Dielectric constant exists between 24 and 29, quality factor ( × ) is ranging between 15,236 and 22,020 GHz with a slight increase than those recorded with commercial alumina (10,000 – 20,000 GHz) and temperature coefficient of resonant frequency (f) in the –69 to –83 ppm/°C range. The addition of SrO up to 5 wt% leads to a maximum (r) value (29) due to relatively higher ionic polarizability of Sr2+ than that of the Al3+ and B3+ ions. On the other hand, changing chemical and phase composition with the formation of platelets of Sr-hexaluminate phase (SrAl12O19) results in maximizing value of ( × ) up to 22,020 GHz at ≈ 8 GHz and large negative charge of (f) to –83 ppm/°C.

  18. Dielectric Properties of Vesta's Surface as Constrained by Dawn VIR Observations

    CERN Document Server

    Palmer, Elizabeth M; Capria, Maria Teresa; Tosi, Federico

    2015-01-01

    Earth and orbital based radar observations of asteroids provide a unique opportunity to characterize surface roughness and the dielectric properties of their surfaces, as well as potentially explore some of their shallow subsurface physical properties. If the dielectric and topographic properties of asteroid's surfaces are defined, we can constrain their textural characteristics as well as potential subsurface volatile enrichment using the observed radar backscatter. To achieve this objective, we establish the first dielectric model of asteroid Vesta for the case of a dry, volatile-poor regolith -- employing an analogy to the dielectric properties of lunar regolith, and adjusted for the surface densities and temperatures deduced from Dawn's Visible and InfraRed mapping spectrometer (VIR). Our model suggests that the dielectric constant at the surface of Vesta is relatively constant, ranging from 2.0 to 2.1 from the night- to day-side of Vesta, while the loss tangent shows slight variation as a function of diu...

  19. Crystal Structure and Dielectric Properties of Microwave Ceramics CaLa(CaM)O6 [M = Nb, Sb

    Science.gov (United States)

    Dutta, Alo; Mandal, Sanjay; Kumari, Premlata; Mukhopadhyay, P. K.; Biswas, S. K.; Sinha, T. P.

    2017-03-01

    The dielectric properties of two perovskite oxides CaLa(CaM)O6 [M = Nb, Sb] synthesized by the solid-state reaction technique have been studied in the microwave and radio frequency range. The phase formation and the crystal structure of the materials are investigated by the Rietveld refinement of the x-ray diffraction data at room temperature. The Raman spectrum substantiates the crystal structure of the materials. The temperature dependence of the relaxation frequencies in the radio frequency range follows the Arrhenius law, and the corresponding activation energies are found to be 0.339 eV and 0.346 eV, respectively, for CaLa(CaNb)O6 and CaLa(CaSb)O6. The difference in the values of the dielectric constant and the loss tangent are correlated with the respective crystal structure of the materials.

  20. Crystal Structure and Dielectric Properties of Microwave Ceramics CaLa(CaM)O6 [M = Nb, Sb

    Science.gov (United States)

    Dutta, Alo; Mandal, Sanjay; Kumari, Premlata; Mukhopadhyay, P. K.; Biswas, S. K.; Sinha, T. P.

    2017-01-01

    The dielectric properties of two perovskite oxides CaLa(CaM)O6 [M = Nb, Sb] synthesized by the solid-state reaction technique have been studied in the microwave and radio frequency range. The phase formation and the crystal structure of the materials are investigated by the Rietveld refinement of the x-ray diffraction data at room temperature. The Raman spectrum substantiates the crystal structure of the materials. The temperature dependence of the relaxation frequencies in the radio frequency range follows the Arrhenius law, and the corresponding activation energies are found to be 0.339 eV and 0.346 eV, respectively, for CaLa(CaNb)O6 and CaLa(CaSb)O6. The difference in the values of the dielectric constant and the loss tangent are correlated with the respective crystal structure of the materials.

  1. Experimental investigation of the dielectric properties of soil under hydraulic loading

    Science.gov (United States)

    Bittner, Tilman; Bore, Thierry; Wagner, Norman; Karlovšek, Jurij; Scheuermann, Alexander

    2017-04-01

    An experimental set-up was developed in order to determine the coupled hydraulic, dielectric and mechanical properties of granular media under hydraulic loading. The set-up consisted of a modified column for permeability tests involving a flow meter and pressure transducers along the sample to quantify the hydraulic gradient. A newly developed open-ended coaxial probe allowed the measurement of the frequency dependent dielectric permittivity of the material under test. The shear strength of the sample within the column was measured using a conventional vane shear device. In this paper, the overall set-up is introduced with focus on the open-ended coaxial probe. The design and calibration of the probe are introduced in detail. A numerical study showed that the sensitive cylindrical volume of the probe was approximately 150 mm in diameter with a depth of 65 mm. An investigation with glass beads showed that the set-up allowed the parameterization of the hydraulic, mechanic and dielectric parameters of granular materials under the influence of vertical flow. A satisfactorily good correlation between porosity and the real part of the dielectric permittivity was detected. The critical hydraulic gradient defining the transition of a fixed bed of particles to fluidization was characterized by a sharp peak in the evolution of the hydraulic conductivity and could easily be determined from the measurements. The shear strength of the material under test reduces linearly with increasing hydraulic gradient. Future investigations will be carried out to provide the required parameterizations for experimental and numerical investigations of the internal erosion of granular media.

  2. Dielectric Properties of Lead Monoxide Filled Unsaturated Polyester Based Polymer Composites

    Science.gov (United States)

    Harish, V.; Kumar, H. G. Harish; Nagaiah, N.

    2011-07-01

    Lead monoxide filled isophthalate resin particulate polymer composites were prepared with different filler concentrations and investigated for physical, thermal, mechanical and gamma radiation shielding characteristics. This paper discusses about the dielectric properties of the composites. The present study showed that the dielectric constant (ɛ'), dielectric loss (ɛ″) and ac conductivity (σac) of isopthalate based unsaturated polyester resin increases with the increase in wt% PbO filler in polymer matrix.

  3. Properties of Atmospheric Pressure Ar Plasma Jet Depending on Treated Dielectric Material

    Science.gov (United States)

    Prysiazhnyi, Vadym; Ricci Castro, Alonso H.; Kostov, Konstantin G.

    2017-02-01

    Atmospheric pressure plasma jet operated in argon was utilized to modify surfaces of glass, acrylic, and PTFE dielectrics. This paper describes the influence of the dielectric substrate on operation and properties of plasma. Two modes of operation (each of those have two patterns) were described. The transition from one mode to another, values of the dissipated power, and spreading of plasma over the dielectric surfaces strongly depended on the substrate material. Additionally, three methods of plasma spreading estimation were presented and discussed.

  4. Dielectric properties of portland cement paste as a function of time since mixing

    Science.gov (United States)

    Camp, Paul R.; Bilotta, Stephen

    1989-12-01

    The dielectric properties of portland cement paste and mortar have been measured in the frequency range 100 Hz-7 MHz as a function of time since mixing. Over much of the spectrum, the ac conductance of the samples appears directly related to the amount of unbound water remaining in the sample and ionic conduction predominates. In addition, interesting structure was found in both the conductance and capacitance data at high frequencies as the free water content was reduced. We conclude that relatively simple measurements of this kind can be a useful tool in concrete research and may provide the basis for simple, in situ, nondestructive measurement of the degree of curing of concrete or for monitoring water migration in concrete structures. Measurements on sealed samples of partially or fully cured concrete reveal also the water-cement ratio of the original mix.

  5. Carbon materials with quasi-graphene layers: The dielectric, percolation properties and the electronic transport mechanism

    Institute of Scientific and Technical Information of China (English)

    Lu Ming-Ming; Yuan Jie; Wen Bo; Liu Jia; Cao Wen-Qiang; Cao Mao-Sheng

    2013-01-01

    We investigate the dielectric properties of muhi-walled carbon nanotubes (MWCNTs) and graphite filling in SiO2 with the filling concentration of 2-20 wt.% in the frequency range of 102-107 Hz.M WCNTs and graphite have general electrical properties and percolation phenomena owing to their quasi-structure made up of graphene layers.Both permittivity ε and conductivity σ exhibit jumps around the percolation threshold.Variations of dielectric properties of the composites are in agreement with the percolation theory.All the percolation phenomena are determined by hopping and migrating electrons,which are attributed to the special electronic transport mechanism of the fillers in the composites.However,the twin-percolation phenomenon exists when the concentration of MWCNTs is between 5-10 wt.% and 15-20 wt.% in the MWCNTs/SiO2 composites,while in the graphite/SiO2 composites,there is only one percolation phenomenon in the graphite concentration of 10-15 wt.%.The unique twin-percolation phenomenon of MWCNTs/SiO2 is described and attributed to the electronic transfer mechanism,especially the network effect of MWCNTs in the composites.The network formation plays an essential role in determining the second percolation threshold of MWCNTs/SiO2.

  6. Investigations on electrical conductivity and dielectric properties of Na doped ZnO synthesized from sol gel method

    Energy Technology Data Exchange (ETDEWEB)

    Tabib, Asma; Sdiri, Nasr [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Elhouichet, Habib, E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, University Tunis El Manar, Tunis 2092 (Tunisia); Férid, Mokhtar [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia)

    2015-02-15

    Highlights: • ZnO nanoparticles doped with Na were prepared from sol-gel method. • Electric conductivity and dielectric properties were investigated. • The ZnO conductivity is estimated to be of p-type for critical Na doping of 1.5% at. - Abstract: Na doped ZnO nanoparticles (NPs) were elaborated by sol gel technique. The X-ray diffraction patterns show that the peaks are indexed to the hexagonal structure without any trace of an extra phase. Electric and dielectric properties were investigated using complex impedance spectroscopy. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). The contribution of grain boundary resistance to the total resistance of the system is remarkable. The AC conductivity increases with temperature following the Arrhenius law, with single apparent activation energy for conduction process. The frequency dependence of the electric conductivity follows a simple power law behavior, in according to relation σ{sub AC}(ω) = σ(0) + A ω{sup s}, where s is smaller than 1. The analysis of dc conductivity indicates that the conduction is ionic in nature. The study of its variation, at fixed temperature, with Na content shows sharp decrease which is explained by the formation of Na{sub Zn} acceptor. It was found that the dc conductivity reaches its minimum value for critical Na concentration of 1.5% at which the conductivity is estimated to be of p-type. Impedance and modulus study reveals the temperature dependent non-Debye type relaxation phenomenon. Dielectric studies revealed a promising dielectric properties (relatively high ε′ at low frequencies and low loss at high frequencies). In the low-frequency region, the values of M′ tends to zero suggesting negligible or absent electrode polarization phenomenon. The frequency dependent maxima in the imaginary modulus are found to obey to Arrhenius law.

  7. Dielectric Property Enhancement in Polymer Composites with Engineered Interfaces

    Science.gov (United States)

    Krentz, Timothy Michael

    This thesis reports studies into the dielectric behavior of polymer composites filled with silica nanoparticles. The permittivity and dielectric breakdown strength (DBS) of these materials are critical to their performance in insulating applications such as high voltage power transmission. Until now, the mechanisms which lead to improvements in DBS in these systems have been poorly understood, in part because the effects of dispersion of the filler and the filler's surface electronic characteristics have been confused. The new surface modifications created in this thesis permit these two parameters to be addressed independently, leading to the hypothesis that nanocomposite dielectric materials exhibit DBS enhancement when electron avalanches are prevented from proceeding to reach a critical size capable of causing failure. The same control of dispersion and surface properties also lead to changes in the permittivity of the composite based upon the polarizability and trapping behavior of the filler. In this work, the dispersion and surface states of silica nanoparticles were independently controlled with two separate populations of surface molecules. Two matrix materials were studied, and in each system, a different, matrix-compatible long chain polymer is required to control dispersion. Conversely, a second population of short molecules is shown to be capable of creating electronic traps associated with the silica nanoparticle surface which lead to DBS enhancements largely independent of the matrix, indicating that the same failure mechanism is operating in both epoxy and polypropylene. Progressive variation in dispersion quality is attained with this surface modification scheme. This creates progressively smaller volumes of matrix polymer unaffected by the filler. This work shows that when these volumes approach and become smaller than the same scale as predicted for electron avalanches, the greatest changes in DBS are seen. Likewise, the plateau behavior of this

  8. Electro-optical and dielectric properties of a high tilt antiferroelectric liquid crystal mixture (W-193B)

    Energy Technology Data Exchange (ETDEWEB)

    Nayek, Prasenjit; Ghosh, Sharmistha; Kundu, Sudarshan; Roy, Subir Kr [Department of Spectroscopy, Indian Association for the Cultivation of Science, Jadavpur, Calcutta-700032 (India); Majumder, Tapas Pal [Department of Physics, University of Kalyani, Kalyani-741235, West Bengal (India); Bennis, Noureddine; Oton, Jose Manuel [Department of TecnologIa Fotonica, ETSI Telecomunicacion, Universidad Politecnica de Madrid, Ciudad Universitaria, 28040 Madrid (Spain); Dabrowski, Roman, E-mail: spskr@iacs.res.i [Institute of Chemistry, Military University of Technology, 00-908 Warsaw (Poland)

    2009-11-21

    The electro-optical properties and dielectric relaxation have been investigated for an antiferroelectric liquid crystal mixture W-193B. The material exhibits smectic A*, smectic C* and a wide range of anticlinic smectic C{sub A}{sup *} phases. The high tilt and broad room temperature smectic C{sub A}{sup *} phase make it a good candidate for antiferroelectric display materials. Dielectric studies have been made in a planarly aligned cell in the frequency range 10 Hz-13 MHz. Dielectric spectroscopy reveals the existence of soft mode in the smectic A* phase and Goldstone mode in the smectic C* phase. In the smectic C{sub A}{sup *} phase the dielectric spectrum of the material exhibits two absorption peaks related to the rotational fluctuation around the short axis of the molecules and antiphase azimuthal angle fluctuation, respectively, and are separated by about two orders of frequency. Electro-optical response using a low frequency triangular wave showed a very high quasi-static contrast ratio of 132 : 1, threshold voltage of around 7 V and saturation of 17 V. Surface-stabilized, low thickness cells of this mixture showed a perfect double hysteresis loop with a 1 Hz triangular signal, reaching different transmission levels for different voltage amplitudes. These levels can be stabilized with a single holding voltage, making it possible for the material to be passively multiplexed at video rate.

  9. Influence of particle size and temperature on the dielectric properties of CoFe2O4 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Deepshikha Rathore; Rajnish Kurchania; R. K. Pandey

    2014-01-01

    The objective of this study was to establish the dielectric properties of CoFe2O4 nanoparticles with particle sizes that varied from 28.6 to 5.8 nm. CoFe2O4 nanoparticles were synthesized using a chemical coprecipitation method. The particle sizes were calculated accord-ing to the Scherrer formula using X-ray diffraction (XRD) peaks, and the particle size distribution curves were constructed by using field-emission scanning electron microscopy (FESEM) images. The dielectric permittivity and loss tangents of the samples were determined in the frequency range of 1 kHz to 1 MHz and in the temperature range of 300 to 10 K. Both the dielectric permittivity and the loss tangent were found to decrease with increasing frequency and decreasing temperature. For the smallest CoFe2O4 nanoparticle size, the dielectric per-mittivity and loss tangent exhibited their highest and lowest values, respectively. This behavior is very useful for materials used in devices that operate in the microwave or radio frequency ranges.

  10. THE EFFECT OF DIFFERENT POLYMORPHS TiO2 RAW MATERIALS ON THE DIELECTRIC PROPERTIES AND MICROSTRUCTURE IN CaCu3Ti4O12 CERAMICS

    Directory of Open Access Journals (Sweden)

    Hao W.

    2013-09-01

    Full Text Available CaCu3Ti4O12 ceramics with different polymorphs of TiO2 as starting materials were prepared by the conventional solid-state reaction technique. Their crystalline structure, microstructure and dielectric properties were systematically investigated. It has been found that all of the ceramic specimens prepared in the present study have a good polycrystalline structure, and no secondary phase is been found by XRD. However, large differences in dielectric properties and microstructure are observed in them: 1 the characteristic frequency of dielectric relaxation around 1 MHz in the CCTO ceramics prepared with rutile TiO2 is much lower than that in those ceramics prepared with anatase TiO2; 2 no matter dielectric properties or microstructure, the CCTO ceramics prepared with rutile TiO2 are more sensitive to the sintering temperature than those ceramics prepared with anatase TiO2.

  11. Dielectric properties of polyacrylate thick films used in sensors and actuators

    Science.gov (United States)

    Jean-Mistral, C.; Sylvestre, A.; Basrour, S.; Chaillout, J.-J.

    2010-07-01

    Dielectric polymers are emerging electro-active materials used in high performance applications such as micropumps, robots and artificial muscles. The development of such applications requires the use of models taking into account the electrical parameters of the material. However, there is still some controversy over the dielectric constant of the most widely used dielectric polymer (VHB 4910, 3M, USA). In this paper, we present an exhaustive study relating to changes in the dielectric constant of VHB 4910 over wide frequency and temperature ranges. We found that the permittivity was a function of: frequency, temperature, the nature of the electrodes and the pre-stress applied to material. Mechanisms of dielectric polarization (β-relaxation) explain the behaviour in temperature and frequency of this parameter. The use of silver grease-compliant electrodes induces an increase in the dielectric constant which moves to a value of 5.4 (against 4.7 with gold electrodes). A pre-strain applied to the material shows a reduction up to 15% in the value of the dielectric constant. Short-range dipolar relaxation, local mechanical constraints in the material and a possible crystallization of material induced by the stretching are suggested to explain these behaviours. Analytic equations of the dielectric constant according to the temperature and pre-strain are then proposed and used to validate the behaviour of these materials for actuator and scavenger devices.

  12. Effect of Interfacial Polarization and Water Absorption on the Dielectric Properties of Epoxy-Nanocomposites

    Directory of Open Access Journals (Sweden)

    Philipp Marx

    2017-05-01

    Full Text Available Five types of nanofillers, namely, silica, surface-silylated silica, alumina, surface-silylated alumina, and boron nitride, were tested in this study. Nanocomposites composed of an epoxy/amine resin and one of the five types of nanoparticles were tested as dielectrics with a focus on (i the surface functionalization of the nanoparticles and (ii the water absorption by the materials. The dispersability of the nanoparticles in the resin correlated with the composition (OH content of their surfaces. The interfacial polarization of the thoroughly dried samples was found to increase at lowered frequencies and increased temperatures. The β relaxation, unlike the interfacial polarization, was not significantly increased at elevated temperatures (below the glass-transition temperature. Upon the absorption of water under ambient conditions, the interfacial polarization increased significantly, and the insulating properties decreased or even deteriorated. This effect was most pronounced in the nanocomposite containing silica, and occurred as well in the nanocomposites containing silylated silica or non-functionalized alumina. The alternating current (AC breakdown strength of all specimens was in the range of 30 to 35 kV·mm−1. In direct current (DC breakdown tests, the epoxy resin exhibited the lowest strength of 110 kV·mm−1; the nanocomposite containing surface-silylated alumina had a strength of 170 kV·mm−1. In summary, water absorption had the most relevant impact on the dielectric properties of nanocomposites containing nanoparticles, the surfaces of which interacted with the water molecules. Nanocomposites containing silylated alumina particles or boron nitride showed the best dielectric properties in this study.

  13. Growth and dielectric properties of KTiOPO4 and K1 - x Rb x TiOPO4 crystals

    Science.gov (United States)

    Gurtovoĭ, V. G.; Sheleg, A. U.; Guretskiĭ, S. A.; Kalanda, N. A.

    2008-07-01

    Methods of growth of KTiOPO4 and K1 - x Rb x TiOPO4 crystals of high optical quality have been optimized. The dielectric properties (permittivity and conductivity) of the crystals grown have been investigated at frequencies from 102 to 106 Hz in the temperature range from 100 to 350 K, along the [001] crystallographic direction. It is established that partial substitution of K+ ions with Rb+ ions leads to a decrease in the permittivity and conductivity.

  14. Longitudinal dielectric permeability into quantum degenerate plasma with frequency of collisions proportional to the module of a wave vector

    CERN Document Server

    Latyshev, A V

    2013-01-01

    Formulas for the longitudinal dielectric permeability in quantum degenerate collisional plasma with the frequency of collisions proportional to the module of the wave vector, in Mermin's approach, are received. Equation of Shr\\"{o}dinger - Boltzmann with integral of collisions relaxation type in Mermin's approach is applied. It is spent numerical and graphic comparison of the real and imaginary parts of dielectric function of non-degenerate and maxwellian collisional quantum plasma with a constant and a variable frequencies of collisions. It is shown, that the longitudinal dielectric function weakly depends on a wave vector.

  15. Consequence of cobalt on structural, optical and dielectric properties in ZnO nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Zia, Amir, E-mail: amirziaphysics@hotmail.com [Center for Emerging Sciences, Engineering & Technology (CESET), Islamabad (Pakistan); Ahmed, S. [Center for Emerging Sciences, Engineering & Technology (CESET), Islamabad (Pakistan); Advanced Electronics Laboratory, International Islamic University, Islamabad (Pakistan); Shah, N.A.; Anis-ur-Rehman, M. [COMSATS, Institute of Information Technology, Islamabad (Pakistan); Khan, E.U. [Center for Emerging Sciences, Engineering & Technology (CESET), Islamabad (Pakistan); Basit, M. [Centre for Solid State Physics, Punjab University (Pakistan)

    2015-09-15

    The critical role of cobalt dopant in ZnO nanostructures with different cobalt concentrations has been explored on the basis of structural, optical and dielectric mechanisms. X-ray diffraction (XRD) analysis shows that the Co{sup +2} ions replace Zn{sup +2} ions in the ZnO matrix, producing lattice strain. Diffused Reflectance Spectroscopy (DRS) shows a red shift in optical energy band gap with increase in cobalt content, along with the presence of transitions in high spin states due to tetrahedrally coordinated cobalt ions. The dielectric characterization explains the disparity in dynamic dielectric parameters like capacitance, dielectric constant, tangent loss, AC conductivity and impedance as a function of frequency. Capacitance and both static and dynamic dielectric constants found to be decreasing with cobalt addition. The anomaly in these pronounced parameters can address the key problems of the material at higher frequencies device operation.

  16. Dielectric Properties of Water in Butter and Water-AOT-Heptane Systems Measured using Terahertz Time-Domain Spectroscopy

    DEFF Research Database (Denmark)

    Møller, Uffe; Folkenberg, Jacob Riis; Jepsen, Peter Uhd

    2010-01-01

    We investigate the dielectric properties of water confined in nanometer-sized inverse micelles in mixtures of water, AOT, and heptane. We show that the dielectric properties of the confined water are dependent on the water pool size and different from those of bulk water. We also discuss the diel...... the dielectric properties of different vegetable oils, lard, and butter, and use these properties to deduce the dielectric properties of water in butter, which are shown to deviate significantly from the dielectric properties of bulk water....

  17. Spectral and angular characteristics of dielectric resonator metasurface at optical frequencies

    Energy Technology Data Exchange (ETDEWEB)

    Zou, Longfang [School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA 5005 (Australia); Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH (United Kingdom); López-García, Martin; Oulton, Ruth; Klemm, Maciej [Department of Electrical and Electronic Engineering, The University of Bristol, Bristol, BS8 1TH (United Kingdom); Withayachumnankul, Withawat; Fumeaux, Christophe, E-mail: christophe.fumeaux@adelaide.edu.au [School of Electrical and Electronic Engineering, The University of Adelaide, Adelaide, SA 5005 (Australia); Shah, Charan M.; Mitchell, Arnan; Bhaskaran, Madhu; Sriram, Sharath [Functional Materials and Microsystems Research Group, School of Electrical and Computer Engineering, RMIT University, Melbourne VIC 3001 (Australia)

    2014-11-10

    The capability of manipulating light at subwavelength scale has fostered the applications of flat metasurfaces in various fields. Compared to metallic structure, metasurfaces made of high permittivity low-loss dielectric resonators hold the promise of high efficiency by avoiding high conductive losses of metals at optical frequencies. This letter investigates the spectral and angular characteristics of a dielectric resonator metasurface composed of periodic sub-arrays of resonators with a linearly varying phase response. The far-field response of the metasurface can be decomposed into the response of a single grating element (sub-array) and the grating arrangement response. The analysis also reveals that coupling between resonators has a non-negligible impact on the angular response. Over a wide wavelength range, the simulated and measured angular characteristics of the metasurface provide a definite illustration of how different grating diffraction orders can be selectively suppressed or enhanced through antenna sub-array design.

  18. Dielectric Behaviour of Zn/Al-NO3 LDHs Filled with Polyvinyl Chloride Composite at Low Microwave Frequencies

    OpenAIRE

    Ethar Y. Salih; Zulkifly Abbas; Samer Hasan Hussein Al Ali; Mohd Zobir Hussein

    2014-01-01

    Recently, researchers have shown great interest in improving the thermal, mechanical, dielectric, and microwave properties of pure polymers through the use of polymer-based composites. The essential properties of polymer-based composites can be modified by varying the amount of Zn/Al-NO3 layered double hydroxide (LDH) added to polyvinyl chloride (PVC). Therefore, by determining the optimal ratio of LDH in the PVC matrix, the dielectric properties of PVC-LDH composites can be improved. An LDH ...

  19. Lanthanum titanium perovskite compound: Thin film deposition and high frequency dielectric characterization

    Energy Technology Data Exchange (ETDEWEB)

    Le Paven, C., E-mail: claire.lepaven@univ-rennes1.fr [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Lu, Y. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Nguyen, H.V. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); CEA LETI, Minatec Campus, 38054 Grenoble (France); Benzerga, R.; Le Gendre, L. [Institut d' Electronique et de Télécommunications de Rennes (IETR, UMR-CNRS 6164), Equipe Matériaux Fonctionnels, IUT Saint Brieuc, Université de Rennes 1, 22000 Saint Brieuc (France); Rioual, S. [Laboratoire de Magnétisme de Brest (EA CNRS 4522), Université de Bretagne Occidentale, 29000 Brest (France); Benzegoutta, D. [Institut des Nanosciences de Paris (INSP, UMR CNRS 7588), Université Pierre et Marie Curie, 75005 Paris (France); Tessier, F.; Cheviré, F. [Institut des Sciences Chimiques de Rennes (ISCR, UMR-CNRS 6226), Equipe Verres et Céramiques, Université de Rennes 1, 35000 Rennes (France); and others

    2014-02-28

    Perovskite lanthanum titanium oxide thin films were deposited on (001) MgO, (001) LaAlO{sub 3} and Pt(111)/TiO{sub 2}/SiO{sub 2}/(001)Si substrates by RF magnetron sputtering, using a La{sub 2}Ti{sub 2}O{sub 7} homemade target sputtered under oxygen reactive plasma. The films deposited at 800 °C display a crystalline growth different than those reported on monoclinic ferroelectric La{sub 2}Ti{sub 2}O{sub 7} films. X-ray photoelectron spectroscopy analysis shows the presence of titanium as Ti{sup 4+} ions, with no trace of Ti{sup 3+}, and provides a La/Ti ratio of 1.02. The depositions being performed from a La{sub 2}Ti{sub 2}O{sub 7} target under oxygen rich plasma, the same composition (La{sub 2}Ti{sub 2}O{sub 7}) is proposed for the deposited films, with an unusual orthorhombic cell and Cmc2{sub 1} space group. The films have a textured growth on MgO and Pt/Si substrates, and are epitaxially grown on LaAlO{sub 3} substrate. The dielectric characterization displays stable values of the dielectric constant and of the losses in the frequency range [0.1–20] GHz. No variation of the dielectric constant has been observed when a DC electric field up to 250 kV/cm was applied, which does not match a classical ferroelectric behavior at high frequencies and room temperature for the proposed La{sub 2}Ti{sub 2}O{sub 7} orthorhombic phase. At 10 GHz and room temperature, the dielectric constant of the obtained La{sub 2}Ti{sub 2}O{sub 7} films is ε ∼ 60 and the losses are low (tanδ < 0.02). - Highlights: • Lanthanum titanium oxide films were deposited by reactive magnetron sputtering. • A La{sub 2}Ti{sub 2}O{sub 7} chemical composition is proposed, with an unusual orthorhombic cell. • At 10 GHz, the dielectric losses are lower than 0.02. • No variation of the dielectric constant is observed under DC electric biasing.

  20. Semiconducting and dielectric properties of barium titanates, tantalates and niobates with perovskite structure

    Science.gov (United States)

    Kolodiazhnyi, Taras

    The dielectric and semiconducting properties of two types of ceramics (n-type BaTiO3 and dielectric Ba(B'1/3 B″2/3)O3 where B' = Mg, Zn, Ni, and B″ = Nb, Ta) were characterized. Complex impedance analysis and dc conductivity measurements of samples prepared at various PO2 have ruled out oxygen chemisorption in favor of interfacial segregation of cation vacancies as the cause of the positive temperature coefficient of resistivity (PTCR) effect in n-type BaTiO3. The effect of preparation conditions, sintering atmosphere, stoichiometry, and post-sinter anneal on the defect chemistry of BaTiO3 was studied using the electron paramagnetic resonance (EPR) technique. Several paramagnetic defects such as, Ti3+, VBa, and VTi were detected and identified by EPR. Current-voltage characteristics (I-V) of PTCR BaTiO 3 were analyzed in light of space-charge-limited-current, trap-filled-limited-current, Frenkel-Poole, small polaron, and double-Schottky barrier models. It was shown that for the double-Schottky barrier model, a partial stabilisation of the potential barrier is expected when the Fermi level is pinned at grain boundaries by a high density of the interface states. The deviation of I-V characteristics of BaTiO3 in the region of the PTCR effect can be explained by dependence of the population of the interface electron states on applied voltage. Based on the Seebeck and Hall effect measurements, it was found that in the range of 100--300 K, the drift mobility of electrons in BaTiO 3 is not thermally activated, which supports the concept of conduction band electron transport rather than small radii polaron hopping. However, further study over a wider temperature range and on better quality crystals is required to unequivocally clarify the electron transport mechanism in BaTiO 3. Phase composition, degree of cation ordering, and dielectric properties of complex perovskites with general formula Ba(B' 1/3B″2/3)O3 where B' = Mg, Zn, Ni, and B″ = Nb, Ta were analyzed

  1. Enhancement in dielectric and magnetic properties of Ni–Zn ferrites prepared by sol–gel method

    Energy Technology Data Exchange (ETDEWEB)

    Nasir, S. [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan. (Pakistan); Department of Materials Science and Engineering, Zhejiang University (China); Saleemi, A.S.; Fatima-tuz-Zahra [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan. (Pakistan); Anis-ur-Rehman, M., E-mail: marehman@comsats.edu.pk [Applied Thermal Physics Laboratory, Department of Physics, COMSATS Institute of Information Technology, Islamabad 44000, Pakistan. (Pakistan)

    2013-09-25

    Highlights: •Cr-Zn co-doped Ni-Zn ferrites were prepared with a newly reported sol gel method. •Phase purity and a very good control of crystallite and particle size are obtained. •Low eddy current losses are obtained due to low dielectric losses. •Operational frequency of doped Ni-Zn ferrites could be increased up to GHz ranges. -- Abstract: Due to its high permeability, Mn–Zn ferrite is the material of choice for high frequency applications up to a few MHz. At increased operational frequency, Ni–Zn ferrites are more suitable than Mn–Zn ferrites due to their low eddy current losses and low dielectric losses. To combine all these properties and to increase the operational frequency up to GHz, we have prepared Ni{sub 0.5}Zn{sub 0.5}Cr{sub x}Mn{sub 0.5−x}Fe{sub 1.5}O{sub 4} (x = 0.1, 0.2, 0.3, 0.4, 0.5), with a simplified sol gel method. Prepared samples show high saturation magnetization, low coercivity, and low dielectric loss. The dielectric loss in the frequency range 1 MHz to 1.3 GHz remained almost constant as the Cr content was increased in the samples. The crystallite size and lattice parameters of these samples were calculated from X-ray Diffraction (XRD) data analysis. The crystallite size for each sample was calculated using the Scherrer formula considering the most intense peak (3 1 1) and the results were compared with the Scanning Electron Microscope (SEM) images of these samples. Powder X-ray diffraction (XRD) patterns confirmed the single phase spinel structure for these samples. Wayne Kerr Precession Component Analyzer 6440B and Agilent E4991 Impedance Analyzer were used to study the dielectric constant (ε′) and the dielectric loss tangent (tan δ) of these samples as a function of frequency in the frequency range 100 Hz to 1 MHz and 1 MHz to 1.29 GHz respectively. Quantum design PPMS model 6700 was used to study the magnetic properties of these samples.

  2. Dielectric Properties and Thermal Decomposition of K2Ni(SO4)2 Crystals

    Science.gov (United States)

    Marzougui, H.; Sánchez, V.; León-Luis, S. F.; Lozano-Gorrín, A. D.; Lalla, E.; Torres, M. E.; Attia-Essaies, S.; Ben Hassen-Chehimi, D.

    2016-11-01

    The dielectric properties of K2Ni(SO4)2 crystals have been measured as a function of frequency (100 Hz to 1 MHz) and temperature (400 K to 900 K). The results show that the real part of the conductivity follows the universal dielectric response, where the activation energy varies from 0.72 eV up to 1.08 eV for the temperature range studied. On the other hand, the permittivity and conductivity parameters present a change in their frequency dependence at around 620 K, suggesting that a phase transition might be taking place. To understand this unexpected result, complementary study by thermogravimetric and differential thermal analyses, X-ray powder diffraction analysis, and Raman spectroscopy measurements was carried out. The results suggest thermal decomposition of the original compound at 620 K as follows: 2K2Ni(SO4)2 → K2Ni2(SO4)3 + K2SO4.

  3. Dielectric property of NiTiO{sub 3} doped substituted ortho-chloropolyaniline composites

    Energy Technology Data Exchange (ETDEWEB)

    Lakshmi, Mohana; Faisal, Muhammad [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Roy, Aashish S. [Department of Materials Science, Gulbarga University, Gulbarga-585106, Karnataka (India); Khasim, Syed, E-mail: syed.pes@gmail.com [Department of Physics, PES Institute of Technology, BSC, Bangalore- 560100 (India); Department of Physics, University of Tabuk-71491 (Saudi Arabia); Sajjan, K. C. [Department of Physics, Veerashaiva College, Bellary - 583 104, Karnataka (India); Revanasiddappa, M. [Department of Chemistry, PES Institute of Technology, BSC, Bangalore - 560100 (India)

    2013-11-15

    Ortho-chloropolyaniline (OCP)-NiTiO{sub 3} composites have been synthesized via in-situ polymerization of ortho-chloroaniline with various weight percentages of NiTiO{sub 3.} Fourier Transform Infrared spectroscopic studies of Ortho-chloropolyaniline and its composites indicated the formation of composites as a result of Vander Waal's interaction between OCP and NiTiO{sub 3} particles. Surface morphology of OCP and OCP-NiTiO{sub 3} composites were studied using Scanning Electron Microscope (SEM). The SEM micrographs indicated a modified morphology after the composite formation. Dielectric properties and electric modulus of OCP and OCP-NiTiO{sub 3} composites have been investigated in the frequency range of 50 Hz – 5 MHz. It has been noticed that electrical resistance decreases with increase in weight percentage of NiTiO{sub 3} particles in polymer matrix as well as with applied frequency. The display of semicircular arcs in Cole-Cole plots indicates the formation of series resistor and capacitor in network causing a decrease in the relaxation time and as a result conductivity enhances in these composites. The facile and cost effective synthesis process and excellent dielectric and conductivity response of these materials makes them promising materials for practical applications.

  4. Determination of density of states, conduction mechanisms and dielectric properties of nickel disulfide nanoparticles

    Directory of Open Access Journals (Sweden)

    Arifa Jamil

    2016-05-01

    Full Text Available Temperature and frequency dependent ac electrical measurements were used to explore density of states, conduction mechanisms and dielectric properties of nickel disulfide (NiS2 nanoparticles. The NiS2 nanoparticles were prepared by conventional one step solid state reaction method at 250 °C. X-ray diffraction (XRD confirmed cubic phase of prepared nanoparticles. Scanning electron microscope (SEM images revealed presence of irregular shaped nanoparticles as small as 50 nm. The ac electrical measurements were carried out from 300 K to 413 K. Two depressed semicircular arcs from 20 Hz to 2 MHz showed presence of bulk and grain boundary phases in NiS2 nanoparticles at all temperatures. Small polaron hopping conduction from 300 K to 393 K and correlated barrier hopping conduction mechanism at temperatures higher than 393 K was observed. High value of density of states (of the order of 1024 eV−1cm−3 was calculated from ac conductivity. At low frequencies high values (of the order of 104-107 of real part of dielectric constant (ε′ were observed at different temperatures. These observations suggest that NiS2 nanoparticles may find applications in electronic devices.

  5. Structural, Electrical, Dielectric, and Magnetic Properties of Cd2+ Substituted Nickel Ferrite Nanoparticles

    Directory of Open Access Journals (Sweden)

    B. H. Devmunde

    2016-01-01

    Full Text Available In the present investigation structural, electric, magnetic, and frequency dependent dielectric properties of Ni1-xCdxFe2O4 ferrite nanoparticles (NPs (where x=0.2, 0.4, 0.6, and 0.8 prepared by sol-gel autocombustion method were studied. The crystallite size (t (46.89~58.40 nm was estimated from X-ray diffraction data with the postconfirmation of single phase spinel structure. Spherical shaped, fused grain nature with intergranular diffusion in Ni1-xCdxFe2O4 NPs was observed in scanning electron micrographs. The value of loss tangent (tan⁡δ decreases exponentially with an increasing frequency indicating normal Maxwell-Wagner type dielectric dispersion due to interfacial polarization. Decreasing values of Curie temperature (TC from 860°C to 566°C with increasing Cd2+ content x in Ni1-xCdxFe2O4 NPs were determined from AC-Susceptibility. Activation energy ΔE ranges within 0.03~0.15 eV. Decreasing magnetic saturation Ms, coercivity Hc, and magneton number nB values show the effect on nonmagnetic Cd2+ ions over magnetic Ni2+ and Fe ions.

  6. Electronic and dielectric properties of MoS2-MoX2 heterostructures

    Science.gov (United States)

    Sharma, Munish; Jamdagni, Pooja; Kumar, Ashok; Ahluwalia, P. K.

    2015-05-01

    We present a comparative study of electronic and dielectric properties of MoS2-MoX2 heteostructures (where X=S, Se, Te) within the framework of density functional theory (DFT). Electronic band structure, real & imaginary part of dielectric function, electron energy loss spectra and static dielectric constant have been calculated for each system and compared with one another. A systematic decrease/increase in band gap/static dielectric constant is observed as the X changes from S to Te. These results provide a physical basis for the potential applications of these heterostructures in optoelectronic devices.

  7. Review on dielectric properties of rare earth doped barium titanate

    Science.gov (United States)

    Ismail, Fatin Adila; Osman, Rozana Aina Maulat; Idris, Mohd Sobri

    2016-07-01

    Rare earth doped Barium Titanate (BaTiO3) were studied due to high permittivity, excellent electrical properties and have wide usage in various applications. This paper reviewed on the electrical properties of RE doped BaTiO3 (RE: Lanthanum (La), Erbium (Er), Samarium (Sm), Neodymium (Nd), Cerium (Ce)), processing method, phase transition occurred and solid solution range for complete study. Most of the RE doped BaTiO3 downshifted the Curie temperature (TC). Transition temperature also known as Curie temperature, TC where the ceramics had a transition from ferroelectric to a paraelectric phase. In this review, the dielectric constant of La-doped BaTiO3, Er-doped BaTiO3, Sm-doped BaTiO3, Nd-doped BaTiO3 and Ce-doped BaTiO3 had been proved to increase and the transition temperature or also known as TC also lowered down to room temperature as for all the RE doped BaTiO3 except for Er-doped BaTiO3.

  8. Effect of incorporating aromatic and chiral groups on the dielectric properties of poly(dimethyltin esters).

    Science.gov (United States)

    Baldwin, Aaron F; Ma, Rui; Huan, Tran Doan; Cao, Yang; Ramprasad, Ramamurthy; Sotzing, Gregory A

    2014-12-01

    High-dielectric constant materials are critical for numerous applications such as photovoltaics, photonics, transistors, and capacitors. There are numerous polymers used as dielectric layers in these applications but can suffer from having a low dielectric constant, small band gap, or ferroelectricity. Here, the structure-property relationship of various poly(dimethyltin esters) is described that look to enhance the dipolar and atomic polarization component of the dielectric constant. These polymers are also modeled using first principles calculations based on density functional theory (DFT) to predict such values as the total, electronic, and ionic dielectric constant as well as structure. A strong correlation is achieved between the theoretical and experimental values with the polymers exhibiting dielectric constants >4.5 with dissipation on the order of 10(-3) -10(-2) . © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Controlling dielectric and pyroelectric properties of compositionally graded ferroelectric rods by an applied pressure

    Science.gov (United States)

    Zheng, Yue; Woo, C. H.; Wang, Biao

    2007-06-01

    The polarization, charge offset, dielectric, and pyroelectric properties of a compositionally graded ferroelectric rod inside a high-pressure polyethylene tube are studied using a thermodynamic model based on the Landau-Ginzburg-Devonshire formulation. The calculated distribution of the polarization in the rod is nonuniform, and the corresponding charge offset, dielectric, and pyroelectric properties vary according to the applied pressure. This behavior may be used as a convenient means to control these properties for design optimization.

  10. Infrared dielectric properties of low-stress silicon oxide

    CERN Document Server

    Cataldo, Giuseppe; Brown, Ari D; Miller, Kevin H

    2016-01-01

    Silicon oxide thin films play an important role in the realization of optical coatings and high-performance electrical circuits. Estimates of the dielectric function in the far- and mid-infrared regime are derived from the observed transmittance spectrum for a commonly employed low-stress silicon oxide formulation. The experimental, modeling, and numerical methods used to extract the dielectric function are presented.

  11. Infrared Dielectric Properties of Low-Stress Silicon Oxide

    Science.gov (United States)

    Cataldo, Giuseppe; Wollack, Edward J.; Brown, Ari D.; Miller, Kevin H.

    2016-01-01

    Silicon oxide thin films play an important role in the realization of optical coatings and high-performance electrical circuits. Estimates of the dielectric function in the far- and mid-infrared regime are derived from the observed transmittance spectrum for a commonly employed low-stress silicon oxide formulation. The experimental, modeling, and numerical methods used to extract the dielectric function are presented.

  12. Dielectric and Ferroelectric Properties of Nd-Doped Bi4Ti3O12

    Institute of Scientific and Technical Information of China (English)

    Mao Xiangyu; Chen Xiaobing

    2004-01-01

    The investigations on the ferroelectric and dielectric properties of neodymium-doped Bi4Ti3O12 (Bi4-xNdxTi3 O12 ) ferroelectric ceramics were presented. The ferroelectric properties of Bi4Ti3 O12 were improved by Nd-doping.The dielectric property measurements indicate that the Curie temperatures of Bi4-xNdxTi3O12 decrease with Nd-doping.The variations of dielectric loss suggest that the mobility of the domain wall increases and the oxygen vacancy concentration decreases with doping.

  13. Extraction of Water from Polar Lunar Permafrost with Microwaves - Dielectric Property Measurements

    Science.gov (United States)

    Ethridge, Edwin C.; Kaukler, William

    2009-01-01

    Remote sensing indicates the presence of hydrogen rich regions associated with the lunar poles. The logical hypothesis is that there is cryogenically trapped water ice located in craters at the lunar poles. Some of the craters have been in permanent darkness for a billion years. The presence of water at the poles as well as other scientific advantages of a polar base, have influenced NASA plans for the lunar outpost. The lunar outpost has water and oxygen requirements on the order of 1 ton per year scaling up to as much as 10 tons per year. Microwave heating of the frozen permafrost has unique advantages for water extraction. Proof of principle experiments have successfully demonstrated that microwaves will couple to the cryogenic soil in a vacuum and the sublimed water vapor can be successfully captured on a cold trap. The dielectric properties of lunar soil will determine the hardware requirements for extraction processes. Microwave frequency dielectric property measurements of lunar soil simulant have been measured.

  14. Dielectric Properties of Paper Made from Pulps Loaded with Ferroelectric Particles

    Directory of Open Access Journals (Sweden)

    Hind El Omari

    2016-01-01

    Full Text Available Due to its physical properties and its ease of manufacture, paper is widely used in various engineering applications such as electrical insulation materials for components in high voltage technology. In this study, paper loaded with ferroelectric nanoparticles (BaTiO3 and SrTiO3 was made with fibers obtained from plants growing on the Moroccan soil [Halfa (Stipa tenacissima, Agave (Agave americana, Pennisetum (Pennisetum alopecuroides, Typha (Typha latifolia, and Junc (Juncus effusus] and two commercial pulps (bleached softwood Kraft and newsprint grade thermomechanical pulps. A retention aid, cation polyacrylamide (Percol 292, was necessary to retain ferroelectric particles in the fibrous network and improve the dispersion of strontium titanate particles. The different pulp and handsheets used were characterized according to standard methods (Pulp and Paper Technical Association of Canada, PAPTAC. It is well known that annual and perennial plants contain high percentages of fines (length < 0.2 mm and short fibers. The results show that there is a strong interdependence between the dielectric properties of the loaded paper and surface finish, porosity, dispersion level of ceramic particles, fines content, shape, conformability, and sheet formation. The single dielectric relaxation detected towards low frequencies is attributed to hydroxyl groups present on fiber surfaces, in ceramic particles and adsorbed water.

  15. Calculated Optical Properties of Dielectric Shell Coated Gold Nanorods

    Institute of Scientific and Technical Information of China (English)

    CAO Min; WANG Meng; GU Ning

    2009-01-01

    @@ Optical absorption spectra of dielectric shell coated gold nanorods are simulated using the discrete dipole ap-proximation method. The influence of the aspect ratio, shell thickness, dielectric constant of the shell, and surrounding medium on the longitudinal resonance mode is investigated. It is found that the coated dielectric shell does not affect the trend in the dependence of resonance position on the aspect ratio, while it broadens the resonant line width and reduces the sensitivity of plasmon resonance in response to changes of the surrounding medium. Furthermore, the difference of dielectric constants between the shell and surrounding medium plays an important role in determining the resonance position. The screening effect of the dielectric shell tends to be less apparent for a thicker shell thickness.

  16. Improved Dielectric Model for Polyvinyl Alcohol-Water Hydrogel at Microwave Frequencies

    Directory of Open Access Journals (Sweden)

    You K. Yeow

    2010-01-01

    Full Text Available Problem statement: The study described rigorous dielectric modeling for Polyvinyl Alcohol (PVA-water hydrogel mixture at microwave frequencies. Approach: A commercial open-ended coaxial sensor was used to measure the dielectric constant, loss factor and ionic conductivity, σ of PVA-water hydrogel mixture ranging concentration of 80-100% water content. Results: The sensor was operating between 0.13 and 20 GHz at and above of room temperature (25±1°C. Indirectly, the relaxation time, τ, activation energy, Q and entropy change, ΔS of the hydrogel mixtures are determined based on linear fitting of measured data using Debye and Arrhenius approaches. Conclusion/Recommendations: Two main relaxation processes were found ranging 2-10 and 10-20 GHz, respectively. Dielectric dispersion is suggested to describe by combination of Cole-Davidson (CD and Debye (Dy processes. The results are discussed qualitatively based on bound states of water in hydrogel mixtures.

  17. The review of various synthesis methods of barium titanate with the enhanced dielectric properties

    Energy Technology Data Exchange (ETDEWEB)

    More, S. P., E-mail: smitalomte@gmail.com [MIT college of Engineering, Aurangabad (MS) India (India); Topare, R. J., E-mail: r-topare@yahoo.com [Yogeshwari Mahavidyalaya, Ambajogai (MS) India (India)

    2016-05-06

    The Barium Titanate is a very well known dielectric ceramic belongs to perovskite structure. It has very wide applications in the field of electronic, electro ceramic, electromechanical and electro-optical applications. Barium Titanate has very high dielectric constant as well as low dielectric loss. Substituted dielectrics are one of the most important technological compounds in modern electro ceramics. Its electrical properties can be tuned flexibly by a simple substitution technique. This has encouraged researchers to select a typical cation to be substituted at cationic sites. In the present paper, the review of various synthesis methods of Barium Titanate compound with the effect of different dopants, the grain size on the dielectric properties at various temperatures is discussed.

  18. Temperature dependence dielectric properties of modified barium titanate-PVB composites

    Science.gov (United States)

    Joshi, N. J.; Rakshit, P. B.; Grewal, G. S.; Shrinet, V.; Pratap, A.

    2013-06-01

    In this work, attempts are made to prepare ceramic polymer-composite followed by characterization of dielectric properties. The Barium Titanate ceramic powders are synthesized using the hydrothermal process. Silane treatment is carried out on Barium Titanate powder to increase its compatibility with polymer, followed with preparation of ceramic-polymer composite. Polyvinyl Butyral (PVB) is used as matrix for preparation of the composites and the concentration of Barium Titanate is increased from 60 to 90 wt%. Dielectric properties such as volume resistivity, dielectric constant, dissipation factor are evaluated. Results indicate that the dielectric constant and dissipation factor vary between 52 to 120 and 0.01 to 0.07; respectively as the relative ratio of polymer and silane modified Barium Titanate is varied. Specifically, at 90 wt% of silane modified Barium Titanate, the highest dielectric constant of 123 along with dissipation factor of 0.07 is obtained.

  19. Dielectric studies on the heterogeneity and interfacial property of composites made of polyacene quinone radical polymers and sulfonated polyurethanes.

    Science.gov (United States)

    Zhu, Dan; Zhang, Juan; Bin, Yuezhen; Xu, Chunye; Shen, Jian; Matsuo, Masaru

    2012-03-01

    Sulfonated polyurethane (PUI, matrix) is synthesized and composited with polyacene quinone radical polymers (PAQRs, filler). The polarization mechanism of these polymers and composites were investigated in terms of their frequency, temperature, and filler-concentration-dependent dielectric properties. We found that PUI/PAQR composites have a high permittivity, which is attributed to the filler-matrix interfacial polarization and the contact effect. The PAQR-concentration-dependent permittivity of different PUI/PAQR composites reveals a percolation threshold at 20-30 wt % with scaling exponents that indicate the intercluster polarization. The frequency dependence of dielectric response is well-fitted by using the Debye and Cole-Cole functions on the basis of the structural diagrams and equivalent circuit, leading to a detailed evaluation on heterogeneous structures of different PUI/PAQR composites.

  20. Dielectric properties of betaine phosphite and deuterated betaine phosphite films

    Energy Technology Data Exchange (ETDEWEB)

    Balashova, E. V., E-mail: balashova@mail.ioffe.ru; Krichevtsov, B. B.; Zaitseva, N. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation); Pankova, G. A. [Russian Academy of Sciences, Institute of Macromolecular Compounds (Russian Federation); Frederiks, I. D.; Lemanov, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

    2011-01-15

    Polycrystalline films of betaine phosphite (BPI) and deuterated BPI have been grown by evaporation on LiNbO{sub 3}, {alpha}-SiO{sub 2}, {alpha}-Al{sub 2}O{sub 3}, and NdGaO{sub 3} substrates. These films consist of large single-crystal blocks in which the polar axis (b) lies in the substrate plane. The results of studying the dielectric properties of the films using interdigital electrodes, X-ray diffraction, and block images in a polarized-light microscope in reflection are reported. The film transition into the ferroelectric state at T = T{sub c} is accompanied by strong anomalies of the capacitance of the film/interdigital structure/substrate structure. The deuteration of BPI films leads to an increase in their temperature T{sub c}: from T{sub c} = 200 K for BPI-based structures to T{sub c} = 280 K for structures with a high degree of deuteration (d {approx} 90%).

  1. A model for the scattering of high-frequency electromagnetic fields from dielectrics exhibiting thermally-activated electrical losses

    Science.gov (United States)

    Hann, Raiford E.

    1991-01-01

    An equivalent circuit model (ECM) approach is used to predict the scattering behavior of temperature-activated, electrically lossy dielectric layers. The total electrical response of the dielectric (relaxation + conductive) is given by the ECM and used in combination with transmission line theory to compute reflectance spectra for a Dallenbach layer configuration. The effects of thermally-activated relaxation processes on the scattering properties is discussed. Also, the effect of relaxation and conduction activation energy on the electrical properties of the dielectric is described.

  2. Weak ferromagnetism and temperature dependent dielectric properties of Zn{sub 0.9}Ni{sub 0.1}O diluted magnetic semiconductor

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Raju [Department of Electrical and Electronic Engineering, Shahjalal University of Science and Technology, Sylhet 3114 (Bangladesh); Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Moslehuddin, A.S.M.; Mahmood, Zahid Hasan [Department of Applied Physics, Electronics and Communication Engineering, University of Dhaka, Dhaka 1000 (Bangladesh); Hossain, A.K.M. Akther, E-mail: akmhossain@phy.buet.ac.bd [Department of Physics, Bangladesh University of Engineering and Technology, Dhaka 1000 (Bangladesh)

    2015-03-15

    Highlights: • Single phase wurtzite structure was confirmed from XRD analysis. • Weak ferromagnetic behaviour at room temperature. • Pure semiconducting properties confirmed from temperature dependent conductivity. • Smaller dielectric properties at higher frequency. • Possible potential application in high frequency spintronic devices. - Abstract: In this study the room temperature ferromagnetic behaviour and dielectric properties of ZnO based diluted magnetic semiconductor (DMS) have been investigated using nominal chemical composition Zn{sub 0.9}Ni{sub 0.1}O. The X-ray diffraction analysis confirmed formation of single phase hexagonal wurtzite structure. An increase in grain size with increasing sintering temperature was observed from scanning electron microscopy. Field dependent DC magnetization values indicated dominant paramagnetic ordering along with a slight ferromagnetic behaviour at room temperature. Frequency dependent complex initial permeability showed some positive values around 12 at room temperature. In dielectric measurement, an increasing trend of complex permittivity, loss tangent and ac conductivity with increasing temperature were observed. The temperature dependent dispersion curves of dielectric properties revealed clear relaxation at higher temperature. Frequency dependent ac conductivity was found to increase with frequency whereas complex permittivity and loss tangent showed an opposite trend.

  3. Microwave dielectric properties of BNT-BT0.08 thin films prepared by sol-gel technique

    Science.gov (United States)

    Huitema, L.; Cernea, M.; Crunteanu, A.; Trupina, L.; Nedelcu, L.; Banciu, M. G.; Ghalem, A.; Rammal, M.; Madrangeas, V.; Passerieux, D.; Dutheil, P.; Dumas-Bouchiat, F.; Marchet, P.; Champeaux, C.

    2016-04-01

    We report for the first time the microwave characterization of 0.92(Bi0.5Na0.5)TiO3-0.08BaTiO3 (BNT-BT0.08) ferroelectric thin films fabricated by the sol-gel method and integrated in both planar and out-of-plane tunable capacitors for agile high-frequency applications and particularly on the WiFi frequency band from 2.4 GHz to 2.49 GHz. The permittivity and loss tangent of the realized BNT-BT0.08 layers have been first measured by a resonant cavity method working at 12.5 GHz. Then, we integrated the ferroelectric material in planar inter-digitated capacitors (IDC) and in out-of-plane metal-insulator-metal (MIM) devices and investigated their specific properties (dielectric tunability and losses) on the whole 100 MHz-15 GHz frequency domain. The 3D finite-elements electromagnetic simulations of the IDC capacitances are fitting very well with their measured responses and confirm the dielectric properties determined with the cavity method. While IDCs are not exhibiting an optimal tunability, the MIM capacitor devices with optimized Ir/MgO(100) bottom electrodes demonstrate a high dielectric tunability, of 30% at 2.45 GHz under applied voltages as low as 10 V, and it is reaching 50% under 20 V voltage bias at the same frequency. These high-frequency properties of the MIM devices integrating the BNT-BT0.08 films, combining a high tunability under low applied voltages indicate a wide integration potential for tunable devices in the microwave domain and particularly at 2.45 GHz, corresponding to the widely used industrial, scientific, and medical frequency band.

  4. Low-κ' dielectric properties of UV-treated bi-axially oriented polypropylene films

    Science.gov (United States)

    Dervos, C. T.; Tarantili, P. A.; Athanassopoulou, M. D.

    2009-07-01

    A 40 µm multilayer bi-axially oriented polypropylene (BOPP) film, was fabricated by the tenter process and its dielectric response was investigated after applying combined action of UV, humidity and heat. Dissipation factor (tan δ) and relative dielectric constant measurements were performed via the capacitance method for frequencies 20Hz-1 GHz. These results show that the relative dielectric constant (κ') reduces towards ultra low values (1.8) with an increasing number of applied UV-condensation cycles without any subsequent increase in the dielectric loss. Having no added physical porosity and absence of fluorine atoms, the irradiated BOPP structures offer significant advantages over poly(tetrafluoroethylene) PTFE due to reduced polarization effects, lower dielectric constant values and chemical stability to the adjacent copper or aluminium conductors. Possible application fields are dry type high-voltage capacitors and insulation within electronic components.

  5. Effective dielectric and elastic properties of nanoporous low-k media

    Science.gov (United States)

    Hermann, H.

    2010-07-01

    This paper presents a mathematically defined characterization of random porous media including random self-similarity and surface fractality. The initial two-phase structure is transformed into a three-phase system by introducing the internal surface layer as the third phase. Effective medium theories are utilized to calculate macroscopic dielectric and elastic properties. The dependence of both the static dielectric constant and Young's modulus on geometrical parameters is analyzed for different combinations of bulk and interface properties. It is shown that the modification of the properties of the internal surface layer is a promising way to improve the effective constants of the materials. The obtained analytical expressions are also used to determine confined regions in the space of structural parameters where pre-specified property combinations are realized. The results are discussed in terms of possible applications of nanometer-scale porous interlayer dielectrics with an ultralow dielectric constant and sufficient mechanical stiffness for future semiconducting devices.

  6. Dielectric Properties and Lattice Distortion in Rhombohedral Phase Region and Phase Coexistence Region of PZT Ceramics

    Institute of Scientific and Technical Information of China (English)

    ZHANG Duan-Ming; ZHONG Zhi-Cheng; HAN Xiang-Yun; YAN Wen-Sheng; SUN Hong-Zhang; YANG Feng-Xia; ZHENG Ke-Yu; WEI Nian; LI Zhi-Hua

    2005-01-01

    In this paper, the relation between the dielectric properties and the lattice distortion in the phase coexistence region is discussed using a phase statistical distribution model, and in the rhombohedral phase region the two connection equations on the dielectric properties and the lattice distortion are established. Particularly, the relation between the dielectric properties and the lattice distortion is investigated in the phase coexistence region of PZT ceramics, and the fitting value of the volume fraction of the tetragonal phase VT to composition x in the equation is determined. Further,the fitting results are well consistent with the related experimental data. It involves more profound physical process than relation between the dielectric properties and composition x.

  7. Dielectric properties, impedance analysis and modulus behavior of CaTiO{sub 3} ceramic prepared by solid state reaction

    Energy Technology Data Exchange (ETDEWEB)

    Wong, Y.J., E-mail: yjeng_86@hotmail.com [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hassan, J., E-mail: jumiah@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Hashim, M., E-mail: mansor@science.upm.edu.my [Department of Physics, Faculty of Science, Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia); Advanced Materials and Nanotechnology Laboratory, Institute of Advanced Technology (ITMA), Universiti Putra Malaysia, 43400 Serdang, Selangor (Malaysia)

    2013-09-15

    Highlights: •A single phase orthorhombic CaTiO{sub 3} structure with sub-micron grains is produced. •The frequency exponent ‘s’ is temperature dependent and explained by CBH model. •The dielectric constant and loss tangent are frequency and temperature dependent. •The modulus plot reveals the presence of thermally activated dielectric relaxation. •Cole-cole plot reveals two primary relaxation processes exist in the sample. -- Abstract: Calcium titanate (CaTiO{sub 3}) with the general formula for perovskites, ABO{sub 3}, is of technological importance, particularly with regard to dielectric properties. In this work, CaTiO{sub 3} ceramic material was prepared by the conventional solid state reaction method. The dielectric properties, impedance characteristics and modulus behavior of the CaTiO{sub 3} ceramic material sintered at 1240 °C were investigated in the frequency range of 10{sup −2}–10{sup 6} Hz and temperature range of 100–250 °C. The XRD analysis of the sintered CaTiO{sub 3} shows that it is an orthorhombic structure with lattice parameters a = 5.4398 Å, b = 7.6417 Å, and c = 5.3830 Å. The FESEM micrograph shows a significant difference in grain size distribution ranging from 0.26 to 2.32 μm. The AC conductivity, σ{sub AC}, is found to increase with increasing temperature within the frequency range of 10{sup −2}–10{sup 6} Hz confirming the hopping of electrons to be the conduction mechanism. Due to the decreasing values of the frequency exponent s with increasing temperature, the results of the σ{sub AC} are discussed using the correlated barrier height (CBH) model. For dielectric studies, the dielectric constant, ε′ is found to decrease with increasing frequency. In the whole temperature range of 100–250 °C, high and low frequency plateau are observed. Each converges at high frequency (>10{sup 5} Hz) for all the temperatures. The frequency dependence of loss tangent, tan δ, decreases with rise in temperature, with the

  8. Structures, magnetic and dielectric properties of the ordered double perovskites LnPbNiSbO6 (Ln = La, Pr)

    Science.gov (United States)

    Han, Lin; Bai, Yijia; Liu, Xiaojuan; Yao, Chuangang; Meng, Junling; Liang, Qingshuang; Wu, Xiaojie; Meng, Jian

    2014-09-01

    The crystal structures, magnetic and dielectric properties for the ordered double perovskites LnPbNiSbO6 (Ln = La, Pr) have been investigated. Rietveld refinements of x-ray diffraction data have been indexed for the monoclinic symmetry in space group P21/n (No. 14) and a highly rock-salt ordered arrangement of NiO6 and SbO6 octahedra. The B-site lattices are distorted strongly due to the substitution of rare Earth ions at the A-site. The magnetization measurements show an antiferromagnetic ordering. The effective magnetic moments μ eff are larger than the spin-only values, suggesting that the orbital component for Ni2+ is significant. The maximum values of isothermal magnetization increase due to the lattice distortion of BO6 octahedra, which may weaken the antiferromagnetic interaction via Ni2+-O-Sb5+-O-Ni2+ paths. The dielectric constants for LaPbNiSbO6 present frequency dependence and the tan δ curves exhibit relaxor-like dielectric response. The ɛ‧ decreases with the reduction of the magnetic moments of B-site transition metal ions, which reveals a relationship between the dielectric and magnetic properties.

  9. Improved dielectric properties of nanocomposites based on poly(vinylidene fluoride) and poly(vinyl alcohol)-functionalized graphene.

    Science.gov (United States)

    Wang, Dongrui; Bao, Yaru; Zha, Jun-Wei; Zhao, Jun; Dang, Zhi-Min; Hu, Guo-Hua

    2012-11-01

    In this work, two series of nanocomposites of poly(vinylidene fluoride) (PVDF) incorporated with reduced graphene oxide (rGO) and poly(vinyl alcohol)-modified rGO (rGO-PVA) were fabricated using solution-cast method and their dielectric properties were carefully characterized. Infrared spectroscopy and atom force microscope analysis indicated that PVA chains were successfully grafted onto graphene through ester linkage. The PVA functionalization of graphene surface can not only prevent the agglomeration of original rGO but also enhance the interaction between PVDF and rGO-PVA. Strong hydrogen bonds and charge transfer effect between rGO-PVA and PVDF were determined by infrared and Raman spectroscopies. The dielectric properties of rGO-PVA/PVDF and rGO/PVDF nanocomposites were investigated in a frequency range from 10² Hz to 10⁷ Hz. Both composite systems exhibited an insulator-to-conductor percolating transition as the increase of the filler content. The percolation thresholds were estimated to be 2.24 vol % for rGO-PVA/PVDF composites and 0.61 vol % for rGO/PVDF composites, respectively. Near the percolation threshold, the dielectric permittivity of the nanocomposites was significantly promoted, which can be well explained by interfacial polarization effect and microcapacitor model. Compared to rGO/PVDF composites, higher dielectric constant and lower loss factor were simultaneously achieved in rGO-PVA/PVDF nanocomposites at a frequency range lower than 1 × 10³ Hz. This work provides a potential design strategy based on graphene interface engineering, which would lead to higher-performance flexible dielectric materials.

  10. Preliminary Research on Relationship Between Dielectric Property and Microstructure of Rabbit Liver

    Institute of Scientific and Technical Information of China (English)

    ZHU Jian-bo; SHI Xue-tao; YOU Fu-sheng; WANG Hang; WANG Hui; CAI Zhan-xiu; DONG Xiu-zhen

    2014-01-01

    The dielectric properties in vitro present characteristic changes along with the alteration of metabolic activities, which can be detected from tissue micro-structure. The dielectric properties of tissues are closely related to its viability, but the relationship remains unclear to us. This study aims to specify the relationship between dielectric parameters and microstructure of living tissues and to try to explain the influence of tissue viability on dielectric properties. Nine rabbits were studied in this experiment. The impedance spectroscopy (10 Hz-1 MHz) and microstructure were determined at different time intervals (from 5 min to 7 h) after samples were prepared. Some characteristic parameters were extracted to analyze the relationship between them. The inactivation process characterized by the microstructurs could be detected by means of dielectric parameters:the microstructures had no obvious change within 30 min and cell swelling caused by osmosis led to the decrease of extracellular ion concentration, resulting in the rise of lowfrequency imped ance after 30 min. The reduction of impedance was accompanied by the expanding intercellular area and irregular cell shape caused by the gradual destruction of cell membrane.The functions between alteration rate of intercellular area and Cole-Cole model parameters were also established. There is a strong correlative relationship between dielectric properties and microstructure. The dielectric spectrum can be a rapid and innocuous method to monitor the status of tissues. In the future, it may be of great help for clinical application, especially in transplantation.

  11. Cobalt iron-oxide nanoparticle modified poly(methyl methacrylate) nanodielectrics. Dielectric and electrical insulation properties

    Science.gov (United States)

    Tuncer, Enis; Rondinone, Adam J.; Woodward, Jonathan; Sauers, Isidor; James, D. Randy; Ellis, Alvin R.

    2009-03-01

    In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant.

  12. Computational study of filler microstructure and effective property relations in dielectric composites

    Science.gov (United States)

    Wang, Yu U.; Tan, Daniel Q.

    2011-05-01

    Phase field modeling and computer simulation is employed to study the relations between filler microstructures and effective properties of dielectric composites. The model solves electrostatic equations in terms of polarization vector field in reciprocal space using a fast Fourier transform technique and parallel computing algorithm. Composites composed of linear constituent phases of different dielectric constants are considered. Interphase boundary conditions are automatically taken into account without explicitly tracking interphase interfaces in the composites. Various factors associated with filler microstructures are systematically investigated, including dielectric constant mismatch between fillers and matrix, particle size, shape, orientation, volume fraction, and spatial arrangement as well as directional alignment. Heterogeneous distributions of polarization, charge density, and local electric field are calculated for each composite microstructure, based on which effective dielectric constant and dielectric anisotropy of the composites are determined. It is found that electrostatic interactions among high-dielectric-constant fillers embedded in low-dielectric-constant matrix play critical roles in determining the composite properties, which sensitively depend on filler arrangement and, especially, directional alignment into fibrous microstructures (chains). Such microstructurally engineered composites, whose fillers are not randomly dispersed, exhibit strong dielectric anisotropy despite all constituent components being isotropic.

  13. Charge-order driven multiferroic and magneto-dielectric properties of rare earth manganates

    Indian Academy of Sciences (India)

    Claudy Rayan Serrao; Jyoti Ranjan Sahu; Anirban Ghosh

    2010-04-01

    Charge-order driven magnetic ferroelectricity is shown to occur in several rare earth manganates of the general formula, Ln1–AMnO3 (Ln = rare earth, A = alkaline earth). Charge-ordered manganates exhibit dielectric constant anomalies around the charge-ordering or the antiferromagnetic transition temperature. Magnetic fields have a marked effect on the dielectric properties of these compounds, indicating the presence of coupling between the magnetic and electrical order parameters. Magneto-dielectric properties are retained in small particles of the manganates. The observation of magneto-ferroelectricity in these manganates is in accordance with theoretical predictions.

  14. Effect of Insulation Properties on the Field Grading of Solid Dielectric DC Cable

    DEFF Research Database (Denmark)

    Boggs, S.; Damon, Dwight Hill; Hjerrild, Jesper;

    2001-01-01

    field, however. Based on measured material properties, we demonstrate the effect of such dependencies on the field grading of dc cable for the range of measured material properties and provide an analytical approximation for computing the field of resistively graded dielectrics, including the effect......The development of solid dielectric dc transmission class cable is a priority throughout much of the world, to avoid risks associated with placing hydrocarbon fluids in underwater environments. The conductivity of polymeric solid dielectrics tends to be a strong function of temperature and electric...

  15. Dielectric Properties of ZnTiO3 Microwave Ceramics Consolidated with MgTiO3

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Stabilized ZnTiO3 was prepared by doping magnesium oxide through traditional solid-state reaction. The experimental results indicate that zinc titanate crystals doped with magnesium oxide grow well and the decomposition into Zn2TiO4 and TiO2 is restrained through traditional solid state reaction. By adjusting molar ratio of MgO, better properties can be obtained. The dielectric properties of the ceramics doped with 30% MgO(molar percentage) sintered at 1 060℃ are as follows :the value of quality factor is greater than 20 000 (6.5 GHz), the temperature coefficient of resonance frequency is about 2 × 10-6/℃, the dielectric constant ranges from 18 to 22. Besides, it is proved that heat treatment can optimize microstructure and the value of quality factor, which increases from 23 833.93 to 47 584.00 after 2 h of heat treatment at 1 040 ℃.

  16. Temperature- and frequency-dependent dielectric behaviors of insulator/semiconductor (Al2O3/ZnO) nanolaminates with various ZnO thicknesses

    Science.gov (United States)

    Li, Jin; Bi, Xiaofang

    2016-07-01

    Al2O3/ZnO nanolaminates (NLs) with various ZnO sublayer thicknesses were prepared by atomic layer deposition. The Al2O3 sublayers are characterized as amorphous and the ZnO sublayers have an oriented polycrystalline structure. As the ZnO thickness decreases to a certain value, each NL exhibits a critical temperature at which its dielectric constant starts to rise quickly. Moreover, this temperature increases as the ZnO thickness is decreased further. On the other hand, the permittivity demonstrates a large value of several hundred at a frequency  ⩽1000 Hz, followed by a steplike decrease at a higher frequency. The change in the cut-off frequency with ZnO thickness is characterized by a hook function. It is revealed that the Coulomb confinement effect becomes predominant in the dielectric behaviors of the NLs with very thin ZnO. As the ZnO thickness decreases to about the same as or even smaller than the Bohr radius of ZnO, a great change in the carrier concentration and effective mass of ZnO is induced, which is shown to be responsible for the peculiar dielectric behaviors of Al2O3/ZnO with very thin ZnO. These findings provide insight into the prevailing mechanisms to optimize the dielectric properties of semiconductor/insulator laminates with nanoscale sublayer thickness.

  17. Infrared Dielectric Properties of Low-stress Silicon Nitride

    Science.gov (United States)

    Cataldo, Giuseppe; Beall, James A.; Cho, Hsiao-Mei; McAndrew, Brendan; Niemack, Michael D.; Wollack, Edward J.

    2012-01-01

    Silicon nitride thin films play an important role in the realization of sensors, filters, and high-performance circuits. Estimates of the dielectric function in the far- and mid-IR regime are derived from the observed transmittance spectra for a commonly employed low-stress silicon nitride formulation. The experimental, modeling, and numerical methods used to extract the dielectric parameters with an accuracy of approximately 4% are presented.

  18. Phase evolution and microwave dielectric properties of A5M5O17-type ceramics

    Directory of Open Access Journals (Sweden)

    Ali Murad

    2017-07-01

    Full Text Available A number of A5M5O17 (A = Na, Ca, Sr, La, Nd, Sm, Gd, Dy, Yb; B = Ti, Nb, Ta type compounds were prepared by a solid-state sintering route and characterized in terms of structure, microstructure and microwave dielectric properties. The compatibility of rare earths with mixed niobate/tantalate and titanate phases was investigated. The larger ionic radii mismatch resulted in the formation of pyrochlore and/or mixed phases while in other cases, pure A5M5O17 phase was formed. The samples exhibited relative permittivity in the range of 35 to 82, quality factor (Q × fo = 897 GHz to 11946 GHz and temperature coefficient of resonance frequency (τf = -120 ppm/°C to 318 ppm/°C.

  19. Influence of dielectric constant of polymerization medium on processability and ammonia gas sensing properties of polyaniline

    Indian Academy of Sciences (India)

    Partha Pratim Sengupta; Pradip Kar; Basudam Adhikari

    2011-04-01

    Polyaniline (PANI) was synthesized by the oxidation of aniline hydrochloride in the presence of ammonium persulphate and hydrochloric acid. The polymerization reaction was carried out in several batches in different solvent media by changing the volume ratio of ,-dimethyl formamide (DMF) and water as binary solvent mixture. The dielectric constant of the polymerizationmedium for each batch reaction was determined by measuring the capacitance with change in frequency. The UV spectra of the synthesized polyaniline solutions helped us to optimize the ratio of the binary solvent to get sufficient polymer growth and processability. Thin film of processable polyaniline was then deposited on glass slides coated with polyvinyl alcohol (PVA) crosslinked with maleic anhydride (MA). FTIR and XRD studies of the coated film were also done. AFM studies further helped in the morphological study of the film deposited. Finally, conductivity and ammonia gas-sensing property of the polyaniline film were also studied.

  20. A Method to Adjust Dielectric Property of SiC Powder in the GHz Range

    Institute of Scientific and Technical Information of China (English)

    Xiaolei Su; Jie Xu; Zhimin Li; Junbo Wang; Xinhai He; Chong Fu; Wancheng Zhou

    2011-01-01

    The SiC powders by Al or N doping have been synthesized by combustion synthesis, using Al powder and NH4Cl powder as the dopants and polytetrafluoroethylene as the chemical activator. Characterization by X-ray diffraction, Raman spectrometer, scanning electron microscopy and energy dispersive spectrometer demonstrates the formation of Al doped SiC, N doped SiC and the Al and N co-doped SiC solid solution powders, respectively. The electric permittivities of prepared powders have been determined in the frequency range of 8.2-12.4 GHz. It indicates that the electric permittivities of the prepared SiC powders have been improved by the pure Al or N doping and decrease by the Al and N co-doping. The paper presents a method to adjust dielectric property of SiC powders in the GHz range.

  1. ac conductivity and dielectric properties of amorphous Se{sub 80}Te{sub 20-x}Ge{sub x} chalcogenide glass film compositions

    Energy Technology Data Exchange (ETDEWEB)

    Hegab, N.A. [Physics Department, Faculty of Education, Ain Shams University, Cairo (Egypt)], E-mail: abir_net_2005@hotmail.com; Afifi, M.A.; Atyia, H.E.; Farid, A.S. [Physics Department, Faculty of Education, Ain Shams University, Cairo (Egypt)

    2009-05-27

    Thin films of the prepared Se{sub 80}Te{sub 20-x}Ge{sub x} (x = 5, 7 and 10 at.%) were prepared by thermal evaporation technique. X-ray diffraction patterns showed that the films were in amorphous state. The ac conductivity and dielectric properties of the investigated film compositions were studied in the frequency range 0.1-100 kHz and in temperature range (303-373 K). The experimental results indicated that the ac conductivity and the dielectric properties depended on the temperature and frequency. The ac conductivity is found to obey the {omega}{sup s} law, in accordance with the hopping model, s is found to be temperature dependent (s < 1) and its value goes down as the temperature is increased. The temperature dependence of ac conductivity can be reasonably interpreted in terms of the correlated barrier hopping (CBH) model. Values of dielectric constant {epsilon}{sub 1} and dielectric loss {epsilon}{sub 2} were found to decrease with frequency and increase with temperature. The maximum barrier height W{sub m}, calculated from dielectric measurements according to Guintini equation, agrees with that proposed by the theory of hopping over potential barrier as suggested by Elliott in case of chalcogenide glasses. The density of localized states was estimated for the studied film compositions. The variation of the studied properties with Ge content was also investigated.

  2. Dielectric properties of KDP-type ferroelectric crystals in the presence of external electric field

    Indian Academy of Sciences (India)

    Trilok Chandra Upadhyay; Ramendra Singh Bhandari; Birendra Singh Semwal

    2006-09-01

    Considering external electric field as well as third- and fourth-order phonon anharmonic interaction terms in the pseudospin-lattice coupled mode (PLCM) model Hamiltonian for KDP-type ferroelectrics, expressions for field-dependent shift, width, renormalized soft mode frequency, Curie temperature, dielectric constant and dielectric loss are evaluated. For the calculation, method of statistical double-time temperature-dependent Green's function has been used. By fitting model values of physical quantities, temperature and electric field dependences of soft mode frequency, dielectric constant and loss have been calculated which compare well with experimental results of Baumgartner [8] and Choi and Lockwood [9]. Both dielectric constant and loss decrease with electric field.

  3. Slow-Light Propagation in a Tapered Dielectric Periodic Waveguide over Broad Frequency Range

    Institute of Scientific and Technical Information of China (English)

    FANG Yi-Jiao; CHEN Zhuo; WANG Zhen-Lin

    2011-01-01

    @@ A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric materialis proposed for light trapping.The equifrequency contours(EFC) of silicon-air multilayer photonic crystals within the first bandgap region are first studied.A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted.The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness.Different frequency components of the guiding modes are found to slov and stop at different thicknesses inside such a tapered waveguide structure.In addition,the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.%A tapered waveguide composed of a one-dimensional periodic arrangement of dielectric material is proposed for light trapping. The equifrequency contours (EFC) of silicon-air multilayer photonic crystals within the first bandgap region are first studied. A zero-group-velocity at the first Brillouin zone boundary along the grating vector is predicted. The propagation constants and eigenfrequencies of the first-order guiding modes are numerically investigated for photonic crystal waveguide structures with a finite thickness. Different frequency components of the guiding modes are found to slow and stop at different thicknesses inside such a tapered waveguide structure. In addition, the time-evolution of a femto-second pulse propagating in the tapered waveguide is also demonstrated.

  4. Synthesis, crystal structure, spectroscopic, thermal and dielectric properties of a novel semi-organic pentachloroantimonate (III)

    Science.gov (United States)

    Lahbib, Ikram; Rzaigui, Mohamed; Smirani, Wajda

    2016-09-01

    A new organic-inorganic hybrid material of formula (C10H15N2F)5(SbCl5)5.2H2O was synthesized and characterized by X-Ray diffraction analysis. It crystallizes in the monoclinic space group P21/c with the following unit cell parameters a = 15.819(4) Å, b = 17.685(3) Å, c = 30.529(4) Å, Z = 4 and V = 8540(3) Å3. The examination of the structure shows that the three-dimensional frameworks are produced by Nsbnd H⋯Cl, Nsbnd H⋯O, Csbnd H⋯Cl and Nsbnd H⋯F, Csbnd H⋯F hydrogen bonding and Cl⋯Cl interactions. IR, Raman and UV-Visible spectroscopies were also used to characterize this compound. In addition, the fluorescent properties of this compound have been investigated in the liquid state at room temperature. Differential scanning calorimetry (DSC) has revealed a structural phase transition of the order-disorder type around 370 K. Dielectric investigations revealed a step-wise change of the electric permittivity at Ttr characteristic of the crystal in the high-temperature phase. The evolution of dielectric constant as a function of temperature of the sample has been investigated in order to determine some related parameters. Measurements of AC conductivity as a function of frequency at different temperatures indicated a hopping conduction mechanism and/or reorientational motion.

  5. Magneto-dielectric properties of polymer-Fe{sub 3}O{sub 4} nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Ta-I; Brown, Rene N.C. [Department of Chemical and Biomolecular Engineering, University of Maryland, College Park, MD 20742 (United States); Kempel, Leo C. [Department of Electrical and Computer Engineering, Michigan State University, East Lansing, MI 48824 (United States); Kofinas, Peter [Fischell Department of Bioengineering, University of Maryland, 1120 Jeong H. Kim Building, College Park, MD 20742 (United States)], E-mail: kofinas@umd.edu

    2008-11-15

    The aim of this research is to elucidate the size effect of magnetic nanoparticles on the resultant magneto-dielectric properties of polymer nanocomposites at radio frequencies. The block copolymer of [styrene-b-ethylene/butylene-b-styrene] (SEBS) was utilized as a matrix for the templating of magnetic nanoparticles. Surfactant-modified iron oxide (Fe{sub 3}O{sub 4}) nanoparticles of various sizes were successfully synthesized by a seed-mediated growth method. The surfactant prevented Fe{sub 3}O{sub 4} aggregation and provided compatibility with the polymer matrix. The nucleation and growth of Fe{sub 3}O{sub 4} nanoparticles was controlled by changing the concentration ratio of surfactant to iron-precursor. The free iron ions present during synthesis are the major factor contributing to the growth of larger particles. The Fe{sub 3}O{sub 4} nanoparticle critical size for superparamagnetic to ferrimagnetic transition was determined to be near 30 nm at room temperature. The dielectric permittivity ({epsilon}{sub r}) of the polymer composite increased with increasing amount of Fe{sub 3}O{sub 4} doping, and was not influenced by nanoparticle size. However, the magnetic permeability ({mu}{sub r}) of the composites was significantly influenced by the size of Fe{sub 3}O{sub 4} nanoparticles templated within the block copolymer matrix due to thermal energy fluctuations from the nanoparticle surroundings.

  6. Dielectric properties of FeNbO4 ceramics prepared by the sol-gel method

    Science.gov (United States)

    Devesa, S.; Graça, M. P.; Henry, F.; Costa, L. C.

    2016-11-01

    In this work, FeNbO4 powders were prepared using the sol-gel method. The fine powder particles were pressed into pellets and sintered at temperatures between 500 and 1200 °C. The powder was studied by X-ray diffraction and Raman spectroscopy. The morphology of the grains was investigated by scanning electron microscopy. Heat-treatment of the particles results in higher crystallinity, larger grains, and a decrease in the porosity of the material. The dielectric properties were measured in the frequency range of 102-106 Hz, in function of temperature (200-370 K). In all samples the real (ε‧) and imaginary (ε″) parts of the complex permittivity increase with increasing annealing temperature. The sample heat treated at 1200 °C shows the highest ε‧, > 104 at 300 K. All samples show a dielectric relaxation phenomenon, analysed using the modulus formalism. The evolution of the ac conduction activation energy and of the activation energy associated with the relaxation mechanism, is directly related with the changes promoted by the heat treatment in the structure and in the morphology of the base powders.

  7. Terahertz carrier dynamics and dielectric properties of GaN epilayers with different carrier concentrations

    Science.gov (United States)

    Guo, H. C.; Zhang, X. H.; Liu, W.; Yong, A. M.; Tang, S. H.

    2009-09-01

    Using terahertz time-domain spectroscopy, we measured the complex conductivity and dielectric function of n-type GaN with various carrier concentrations on sapphire substrate. The measured complex conductivity, which is due to the free carriers, is well fitted by simple Drude model. The contribution from the lattice vibration to the complex dielectric function increases with the decrease in free carrier concentration. A better fitting of the frequency-dependent complex dielectric response was obtained by considering both of the Drude and the classical damped oscillator model.

  8. Effect of marination in gravy on the radio frequency and microwave processing properties of beef.

    Science.gov (United States)

    Basaran-Akgul, Nese; Rasco, Barbara A

    2015-02-01

    Dielectric properties (the dielectric constant (ε') and the dielectric loss factor (ε″)) and the penetration depth of raw eye of round beef Semitendinosus muscle, raw beef marinated in gravy, raw beef cooked in gravy, and gravy alone were determined as a function of the temperature (20-130 °C) and frequency (27-1,800 MHz). Both ε' and ε″ values increased as the temperature increased at low frequencies (27 and 40 MHz). At high frequencies (915 and 1,800 MHz), ε' showed a 50 % decrease while ε″ increased nearly three fold with increasing temperature in the range from 20 to 130 °C. ε' increased gradually while ε″ increased five fold when the temperature increased from 20 to 130 °C. Both ε' and ε″ of all samples decreased with increase in frequency. Marinating the beef in gravy dramatically increased the ε″ values, particularly at the lower frequencies. Power penetration depth of all samples decreased with increase temperature and frequency. These results are expected to provide useful data for modeling dielectric heating processes of marinated muscle food.

  9. The low-frequency dielectric response of charged oblate spheroidal particles immersed in an electrolyte

    CERN Document Server

    Hou, Chang-Yu; Sen, Pabitra N

    2016-01-01

    We study the low-frequency polarization response of a surface-charged oblate spheroidal particle immersed in an electrolyte solution. Because the charged spheroid attracts counter-ions which form the electric double layer around the particle, using usual boundary conditions at the interface between the particle and electrolyte can be quite complicated and challenging. Hence, we generalize Fixman's boundary conditions, originally derived for spherical particles, to the case of the charged oblate spheroid. Given two different counter-ion distributions in the thin electric double layer limit, we obtain analytic expressions for the polarization coefficients to the first non-trivial order in frequency. We find that the polarization response normal to the symmetry axis depends on the total amount of charge carried by the oblate spheroid while that parallel to the symmetry axis is suppressed when there is less charge on the edge of the spheroid. We further study the overall dielectric response for a dilute suspensio...

  10. The Interaction of Radio-Frequency Fields With Dielectric Materials at Macroscopic to Mesoscopic Scales

    Science.gov (United States)

    Baker-Jarvis, James; Kim, Sung

    2012-01-01

    The goal of this paper is to overview radio-frequency (RF) electromagnetic interactions with solid and liquid materials from the macroscale to the nanoscale. The overview is geared toward the general researcher. Because this area of research is vast, this paper concentrates on currently active research areas in the megahertz (MHz) through gigahertz (GHz) frequencies, and concentrates on dielectric response. The paper studies interaction mechanisms both from phenomenological and fundamental viewpoints. Relaxation, resonance, interface phenomena, plasmons, the concepts of permittivity and permeability, and relaxation times are summarized. Topics of current research interest, such as negative-index behavior, noise, plasmonic behavior, RF heating, nanoscale materials, wave cloaking, polaritonic surface waves, biomaterials, and other topics are overviewed. Relaxation, resonance, and related relaxation times are overviewed. The wavelength and material length scales required to define permittivity in materials is discussed. PMID:26900513

  11. Opto-structural and dielectric properties of 80 MeV oxygen ion irradiated natural phlogopite mica

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Sukhnandan, E-mail: sukhnandanphy@gmail.com [Department of Physics, Guru Nanak Dev University, Amritsar 143005, Punjab (India); Singh, Surinder; Singh, Lakhwant [Department of Physics, Guru Nanak Dev University, Amritsar 143005, Punjab (India); Lochab, S.P. [Inter University Accelerator Centre, New Delhi 110067 (India)

    2013-04-15

    Highlights: ► Natural phlogopite mica was irradiated with 80 MeV of oxygen ion. ► The opto-structural properties changes due to ion irradiation were investigated. ► Dielectric properties are significantly altered by the irradiation process due to damage. ► FTIR spectra show the shifting of hydroxyl OH stretching band. -- Abstract: Ion beams of MeV energies produce latent tracks in most dielectrics. These ion tracks in turn produce various modifications in their structural, optical and dielectric properties. These modifications are monitored using various techniques such as Ultraviolet–visible spectrometry, X-ray Diffraction, LCR meter and Fourier Transform Infra red spectroscopy in natural phlogopite mica. Thin sheets (∼20 μm) of phlogopite mica were exposed to 80 MeV oxygen ions. A systematic decrease of the optical band gap with ion fluence was observed. An increase in the Urbach energy indicates an increase in the disorder in phlogopite mica. The dielectric constant was found to decrease with increasing fluence while measurements of tan δ, a.c. conductivity and dielectric loss show an increase. The measured data revealed that the value of a.c. conductivity depends linearly on the frequency, with slope n ranging between 0.62 and 0.77. X-ray Diffraction analysis of pristine and irradiated phlogopite mica demonstrated that the crystallite size decreases while strain and dislocation density increases with increasing fluence. Fourier Transform Infra red spectra showed the shifting of the OH stretching band and the disappearance of Si–H bands due to irradiation. Different causes of these modifications are discussed here.

  12. Zirconia doped barium titanate induced electroactive β polymorph in PVDF-HFP: high energy density and dielectric properties

    Science.gov (United States)

    Sharma, Maya; Ranganatha, S.; Kalyani, Ajay Kumar; Ranjan, Rajeev; Madras, Giridhar; Bose, Suryasarathi

    2014-12-01

    Zirconium-doped barium titanate (BZT-08, Ba(Ti0.92 Zr0.08)O3) particles were synthesized and PVDF-HFP-based composites were prepared by melt mixing to design materials with tunable dielectric and ferroelectric properties. Composites of PVDF-HFP and barium titanate (BT) particles were also prepared to realize the exceptional properties associated with the BZT-08-like stabilization of two ferroelectric phases, i.e. tetragonal and orthorhombic at room temperature. To facilitate the uniform dispersion and interfacial adhesion with the matrix, the particles were modified with (3-aminopropyl) triethoxysilane. The dependence of the dielectric and ferroelectric properties of the as-prepared composites were systematically investigated in this study with respect to a wide range of frequencies. The composites with BZT-08 exhibited the significantly high dielectric permittivity of ca. 26 (at 100 Hz) and a high energy density (2.7 J cm-3 measured on 100 μm thick film) at room temperature with respect to the control PVDF-HFP and PVDF-HFP/BT composites. Interestingly, the BZT-08 particles facilitated the electroactive β polymorph in the PVDF-HFP and enhanced polarization in the composites, leading to improved ferroelectric properties in the composites.

  13. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    DEFF Research Database (Denmark)

    Yu, Liyun; Skov, Anne Ladegaard

    2016-01-01

    One prominent method of modifying the properties of dielectric elastomers (DEs) is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting...... metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR) has relatively low viscosity, which is favorable for loading inorganic fillers. In the present...... study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV) were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability...

  14. Structural, microwave dielectric properties and dielectric resonator antenna studies of Sr(Zr{sub x}Ti{sub 1-x})O{sub 3} ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Parida, S. [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Rout, S.K., E-mail: drskrout@gmail.com [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Subramanian, V. [Department of Physics, Indian Institute of Technology Madras, Chennai 600036 (India); Barhai, P.K. [Department of Applied Physics, Birla Institute of Technology, Mesra, Ranchi 835215 (India); Gupta, N.; Gupta, V.R. [Department of Electronics and Communication Engineering, BIT Mesra, Ranchi 835215, Jharkhand (India)

    2012-07-05

    Highlights: Black-Right-Pointing-Pointer XRD and Raman analysis show about phase transition of Sr(Zr{sub x}Ti{sub 1-x})O{sub 3} ceramic. Black-Right-Pointing-Pointer TE{sub 01{delta}} cavity method is used for study of microwave properties of Sr(Zr{sub x}Ti{sub 1-x})O{sub 3} ceramic. Black-Right-Pointing-Pointer The microwave dielectric constant decreased from 253 to 25 and the value of {tau}{sub f} changed from 1771 ppm/ Degree-Sign C to -82 ppm/ Degree-Sign C. - Abstract: Compositionally induced phase transitions in the system Sr(Zr{sub x}Ti{sub 1-x})O{sub 3} were analyzed using a combination of X-ray diffraction, FT-Raman and FTIR spectroscopy. Sr(Zr{sub x}Ti{sub 1-x})O{sub 3} system showed at least two tilting of phase transitions, pm3m-I4mcm and I4/mcm-pnma. The structural transition occurred due to tilting of BO{sub 6} octahedra. Dielectric constant measured with Hakki-Coleman technique decreased from 253 to 25 with increase of Zr content. The value of {tau}{sub f} found 1771 ppm/ Degree-Sign C for SrTiO{sub 3} which decreased to -82 ppm/ Degree-Sign C for the SrZrO{sub 3}. The dielectric resonator antenna (DRA) was investigated experimentally and numerically using a monopole antenna through an infinite ground plane and Ansoft's high frequency structure simulator software, respectively. The required resonance frequency and bandwidth of DRA were investigated in the composition between 0 {<=} x {<=} 1.0.

  15. Microwave Dielectric Properties of A2P2O7 (A = Ca, Sr, Ba; Mg, Zn, Mn)

    Science.gov (United States)

    Bian, Jian-jiang; Kim, Dong-Wan; Hong, Kug Sun

    2004-06-01

    Microwave dielectric properties of A2P2O7 (A = Ca, Sr, Ba, Mn, Mg, Ba) ceramic materials were investigated by a network analyzer at the frequency of 10 GHz. It was found that A2P2O7 ceramics could be sintered at relatively lower temperature below 1150°C, although the thortveitite type series, Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 with smaller ionic radii of A cations were hard to sinter to full density. The dielectric constant of A2P2O7 is lower than 10. The Q× f value increased according to the sequence of δ-Ba2P2O7, α-Sr2P2O7 and β-Ca2P2O7 in dichromatic type series, and the sequence of Mn2P2O7, α-Mg2P2O7 and α-Zn2P2O7 in thortveitite type series, respectively. The temperature coefficient of resonant frequency τf for all samples exhibits negative value. Larger τf for α-Zn2P2O7, α-Mg2P2O7 and δ-Ba2P2O7 is mainly due to their reversible phase transformations. The microwave dielectric properties were discussed from the point view of bond valence.

  16. Raman spectroscopy and microwave dielectric properties of Sn substituted SrLa4Ti5O17 ceramics

    Directory of Open Access Journals (Sweden)

    Manan Abdul

    2016-03-01

    Full Text Available SrLa4Ti5−xSnxO17 (0 ≤ x ≤ 2 ceramics were fabricated through solid state ceramic route and their microwave dielectric properties were investigated in an attempt to tune their temperature coefficient of resonant frequency (τf to zero. The compositions were sintered to single phase SrLa4Ti5O17 and SrLa4Ti4.5Sn0.5O17 ceramics at x = 0 and x = 0.5, and SrLa4Ti4−xSnxO17 along with a small amount of La2Ti2O7 at x = 1. The major phase observed at x = 2 was La2Ti2O7 but along with SrLa4Ti4SnO17 and SrLa4Ti4O15 as the secondary phases. τf decreased from 117 to 23.0 ppm/°C but at the cost of dielectric constant (εr and quality factor multiplied by resonant frequency (Qufo which decreased from 65 to 33.6 and 11150 to 4191 GHz, respectively. The optimum microwave dielectric properties, i.e. τf = 38.6 ppm/°C, εr = 45.5 and Qufo = 7919 GHz, correspond to the SrLa4Ti5−xSnxO17 composition with x = 1.

  17. Issledovanie temperaturnoi i chastotnoi zavisimostei elektrofizicheskikh svoistv dioksida tseriya [Investigation of the temperature and frequency dependences of the electrical properties of cerium dioxide

    Directory of Open Access Journals (Sweden)

    V. A. Ogorodnik

    1993-05-01

    Full Text Available An experimental study of the electrical properties of CeO2 - temperature and frequency dependences of the conductivity, permittivity and dielectric loss tangent, as well as an interpretation of the results obtained

  18. Microwave dielectric and optical properties of amorphous and crystalline Ba0.5Sr0.5TiO3 thin films

    Science.gov (United States)

    Goud, J. Pundareekam; Joseph, Andrews; Ramakanth, S.; Naidu, Kuna Lakshun; Raju, K. C. James

    2016-05-01

    The thin films of composition Ba0.5Sr0.5TiO3 (BST5) were deposited by Pulsed Laser Deposition technique on amorphous fused silica substrates at room temperature (RT) and at 700°C. The film deposited at RT is amorphous while the other crystallized in cubic structure. The refractive index (n) and optical band gap (Eg) extracted from transmission spectra in the 190 -2500 nm range. Microwave dielectric properties were investigated using the Split Post Dielectric Resonators (SPDR) technique at spot frequencies of 10GHz and 20GHz. The experimental results show that thin films deposited at high temperature (700°C) shows very high dielectric constant for both 10GHz and 20 GHz. These high dielectric constant films can be used in a wide range of applications such as capacitors, non-volatile high speed random access memories, and electro-optic devices.

  19. Dielectric Properties of Rhombohedral PbNb2O6

    Directory of Open Access Journals (Sweden)

    Kriti Ranjan Sahu

    2013-01-01

    Full Text Available Dielectric materials are needed in many electrical and electronic applications. So, basic characterizations need to be done for all dielectrics. PbNb2O6 (PN is ferroelectric and piezoelectric only in its orthorhombic phase, with potential high temperature applications. So, its rhombohedral phase, frequently formed as an undesirable impurity in the preparation of orthorhombic PN, has been ignored with respect to possible dielectric characterizations. Here, essentially single phase rhombohedral PN has been prepared, checking structure from XRD Rietveld Analysis, and the real and imaginary parts of permittivity measured in an Impedance Spectrometer (IS up to ~700∘C and over 20 Hz to 5.5 MHz range, for heating and some cooling runs. Variations, with temperature, of relaxation time constant (τ, AC and DC conductivity, bulk resistance, activation energy and capacitance have been explored from our IS data.

  20. Dielectric properties of Ti{sup 4+} substituted BaFe{sub 12}O{sub 19} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Ghoneim, A.I., E-mail: mona_ghoneim@yahoo.com [Physics Department, Faculty of Science, Tanta University, 31527 Tanta (Egypt); Amer, M.A.; Meaz, T.M. [Physics Department, Faculty of Science, Tanta University, 31527 Tanta (Egypt); Attalah, S.S. [Reactor and Neutron Physics Department, Nuclear Research Center, Atomic Energy Authority, Cairo (Egypt)

    2017-02-15

    Series of nanocrystalline BaTi{sub x}Fe{sub 12-(4/3)x}O{sub 19} hexagonal ferrites, 0≤x≤1, was prepared using the chemical co-precipitation method. As-prepared samples were heated at 1200 °C for 20 h and slowly cooled to room temperature (RT). XRD studies proved that the samples have single phase M-type hexagonal nanostructure, where their grain size lies in the range of 42.4 – 61.3 nm. Their dielectric properties were studied against temperature (T) and frequency (F). DC conductivity showed increase against T, whereas AC conductivity showed increase with increasing both T and F. This proved the semiconducting behavior of the samples. Activation energies were found to lie in the range of 0.054–0.169 eV for temperature range of RT ~373 K and of 0.114–0.274 eV for higher temperatures up to 473 K. Variation of the dielectric constant and AC conductivity against F revealed dispersion in all these hexagonal nanostructures, which was assigned to Maxwell–Wagner type of interfacial polarization. Variation of the dielectric loss tangent against F showed a relaxation spectrum for all samples, whereas the dielectric constant and loss tangent showed an increasing trend against T. The relative magnetic permeability μ{sub r} showed an increasing trend with temperature.

  1. Saturation effects on the joint elastic-dielectric properties of carbonates

    Science.gov (United States)

    Han, Tongcheng; Clennell, Michael Ben; Pervukhina, Marina; Josh, Matthew

    2016-06-01

    We used a common microstructural model to investigate the cross-property relations between elastic wave velocities and dielectric permittivity in carbonate rocks. A unified model based on validated self-consistent effective medium theory was used to quantify the effects of porosity and water saturation on both elastic properties (compressional and shear wave velocities) and electromagnetic properties (dielectric permittivity). The results of the forward models are presented as a series of cross-plots covering a wide range of porosities and water saturations and for microstructures that correspond to different predominant aspect ratios. It was found that dielectric permittivity correlated approximately linearly with elastic wave velocity at each saturation stage, with slopes varying gradually from positive at low saturation conditions to negative at higher saturations. The differing sensitivities of the elastic and dielectric rock properties to changes in porosity, pore morphology and water saturation can be used to reduce uncertainty in subsurface fluid saturation estimation when co-located sonic and dielectric surveys are available. The joint approach is useful for cross-validation of rock physics models for analysing pore structure and saturation effects on elastic and dielectric responses.

  2. A possible coupling mechanism between magnetism and dielectric properties in EuTiO3

    Science.gov (United States)

    Jiang, Qing; Wu, Hua

    2002-12-01

    The dielectric constant of an incipient ferroelectric EuTiO3 exhibits a sharp decrease at about 5.5K, at which the antiferromagnetic ordering of the Eu spins simultaneously appears. This fact indicates the existence of a coupling between the magnetism and dielectric properties of EuTiO3. We propose a possible coupling mechanism between the magnetic and electrical subsystems as -gsumlsumlanglei,jrangleq2lvec Si·vec Sj. In the framework of soft-mode theory, we have obtained analytically a dielectric constant expression related to the spin correlation of nearest neighbours of Eu ions.

  3. A possible coupling mechanism between magnetism and dielectric properties in EuTiO3

    Institute of Scientific and Technical Information of China (English)

    蒋青; 吴华

    2002-01-01

    The dielectric constant of an incipient ferroelectric EuTiO3 exhibits a sharp decrease at about 5.5K, at which the antiferromagnetic ordering of the Eu spins simultaneously appears. This fact indicates the existence of a coupling between the magnetism and dielectric properties of EuTiO3. We propose a possible coupling mechanism between the magnetic and electrical subsystems as -gIn the framework of soft-mode theory, we have obtained analytically a dielectric constant expression related to the spin correlation of nearest neighbours of Eu ions.

  4. Reflectance properties of one-dimensional metal-dielectric ternary photonic crystal

    Energy Technology Data Exchange (ETDEWEB)

    Pandey, G. N., E-mail: gnpandey2009@gmail.com [Department of Physics, Amity Institute of Applied Sciences, AmityUniversity, Noida (U.P.) (India); Kumar, Narendra [Department of Physics (CASH), Modi University of Science and Technology, Lakshmangarh, Sikar, Rajsthan (India); Thapa, Khem B. [Department of Physics, U I E T, ChhatrapatiShahu Ji Maharaj University, Kanpur- (UP) (India); Ojha, S. P. [Department of Physics IIT, Banaras Hindu University (India)

    2016-05-06

    Metallic photonic crystal has a very important application in absorption enhancement in solar cells. It has been found that an ultra-thin metallic layer becomes transparent due to internal scattering of light through the each interface of the dielectric and metal surfaces. The metal has absorption due to their surface plasmon and the plasmon has important parameters for changing optical properties of the metal. We consider ternary metallic-dielectric photonic crystal (MDPC) for having large probabilities to change the optical properties of the MDPC and the photonic crystals may be changed by changing dimensionality, symmetry, lattice parameters, Filling fraction and effective refractive index refractive index contrast. In this present communication, we try to show that the photonic band gap in ternary metal-dielectric photonic crystal can be significantly enlarged when air dielectric constant is considered. All the theoretical analyses are made based on the transfer matrix method together with the Drude model of metal.

  5. Dielectric Properties of Dy2O3 -Doped ( Ba, Sr) TiO3 Ceramics

    Institute of Scientific and Technical Information of China (English)

    Huang Xinyou; Gao Chunhua; Chen Xiangchong; Zheng Xialian; Huang Guojun; Liu Huiping

    2004-01-01

    The effects of Dy2O3 doping on the dielectric properties of (Ba, Sr)TiO3 series capacitor ceramics prepared using solid-state reaction method were studied. With the increasing of Dy2O3 additive , the dielectric constant (ε) of materials increases to a maximum when w(Dy2O3 ) is about 0.5% ,while the dielectric loss(tanδ) decreases. The BST ceramics with highε ( = 5245 ), low tanδ ( = 0. 0026 ) and high DC breakdown voltage ( = 5.5 mV ·m-1 ) were obtained. The influencing mechanism of Dy2O3 on the dielectric properties of (Ba, Sr)TiO3 ceramics was studied, thus providing the basis for preparation of capacitor ceramics.

  6. Reflectance properties of one-dimensional metal-dielectric ternary photonic crystal

    Science.gov (United States)

    Pandey, G. N.; Kumar, Narendra; Thapa, Khem B.; Ojha, S. P.

    2016-05-01

    Metallic photonic crystal has a very important application in absorption enhancement in solar cells. It has been found that an ultra-thin metallic layer becomes transparent due to internal scattering of light through the each interface of the dielectric and metal surfaces. The metal has absorption due to their surface plasmon and the plasmon has important parameters for changing optical properties of the metal. We consider ternary metallic-dielectric photonic crystal (MDPC) for having large probabilities to change the optical properties of the MDPC and the photonic crystals may be changed by changing dimensionality, symmetry, lattice parameters, Filling fraction and effective refractive index refractive index contrast. In this present communication, we try to show that the photonic band gap in ternary metal-dielectric photonic crystal can be significantly enlarged when air dielectric constant is considered. All the theoretical analyses are made based on the transfer matrix method together with the Drude model of metal.

  7. Structural, dielectric and magnetic properties of cobalt ferrite prepared using auto combustion and ceramic route

    Energy Technology Data Exchange (ETDEWEB)

    Murugesan, C., E-mail: murugesanscience@gmail.com; Perumal, M.; Chandrasekaran, G.

    2014-09-01

    Cobalt ferrite is synthesized by using low temperature auto combustion and high temperature ceramic methods. The prepared samples have values of lattice constant equal to 8.40 Å and 8.38 Å for auto combustion and ceramic methods respectively. The FTIR spectrum of samples of the auto combustion method shows a high frequency vibrational band at 580 cm{sup −1} assigned to tetrahedral site and a low frequency vibrational band at 409 cm{sup −1} assigned to octahedral site which are shifted to 590 cm{sup −1} and 412 cm{sup −1} for the ceramic method sample. SEM micrographs of samples show a substantial difference in surface morphology and size of the grains between the two methods. The frequency dependent dielectric constant and ac conductivity of the samples measured from 1 Hz to 2 MHz at room temperature are reported. The room temperature magnetic hysteresis parameters of the samples are measured using VSM. The measured values of saturation magnetization, coercivity and remanent magnetization are 42 emu/g, 1553 Oe, 18.5 emu/g for the auto combustion method, 66.7 emu/g, 379.6 Oe, and 17.3 emu/g for the ceramic method, respectively. The difference in preparation methods and size of the grains causes interesting changes in electrical and magnetic properties.

  8. Epoxy-based hydrogels investigated by high-frequency dielectric relaxation spectroscopy.

    Science.gov (United States)

    Krakovský, Ivan; Shikata, Toshiyuki; Hasegawa, Ryuta

    2013-11-14

    Using high-frequency dielectric relaxation spectroscopy, nanophase-separated structures of epoxy-based hydrogels were investigated as a function of water content at 25 °C. The dielectric spectra resulting from the hydrogels were reasonably decomposed into two Debye-type and two Cole-Cole-type relaxation modes. The fastest Debye-type mode, found at 8.3 ps, was attributed to the rotational relaxation process of free water molecules in the bulk state. The other Debye-type mode, at ca. 20-34 ps, originates from the exchange process of water molecules that are hydrogen-bonded to the hydrophilic epoxy network portions for free bulk ones. The first Cole-Cole-type mode observed, at ca. 20-370 ps, was assigned to the complicated dynamics for electric dipole moments of the hydrophilic groups in the epoxy networks (mainly monomeric oxyethylene units). The slowest major Cole-Cole-type mode, at 5-29 ns, was attributed to the Maxwell-Wagner-Sillars polarization process and confirmed the presence of the nanophase-separated structures as revealed by the previous small-angle neutron scattering experiments.

  9. Silicone rubbers for dielectric elastomers with improved dielectric and mechanical properties as a result of substituting silica with titanium dioxide

    Directory of Open Access Journals (Sweden)

    Liyun Yu

    2015-10-01

    Full Text Available One prominent method of modifying the properties of dielectric elastomers (DEs is by adding suitable metal oxide fillers. However, almost all commercially available silicone elastomers are already heavily filled with silica to reinforce the otherwise rather weak silicone network and the resulting metal oxide filled elastomer may contain too much filler. We therefore explore the replacement of silica with titanium dioxide to ensure a relatively low concentration of filler. Liquid silicone rubber (LSR has relatively low viscosity, which is favorable for loading inorganic fillers. In the present study, four commercial LSRs with varying loadings of silica and one benchmark room-temperature vulcanizable rubber (RTV were investigated. The resulting elastomers were evaluated with respect to their dielectric permittivity, tear and tensile strengths, electrical breakdown, thermal stability and dynamic viscosity. Filled silicone elastomers with high loadings of nano-sized titanium dioxide (TiO2 particles were also studied. The best overall performing formulation had 35 wt.% TiO2 nanoparticles in the POWERSIL® XLR LSR, where the excellent ensemble of relative dielectric permittivity of 4.9 at 0.1 Hz, breakdown strength of 160 V µm−1, tear strength of 5.3 MPa, elongation at break of 190%, a Young’s modulus of 0.85 MPa and a 10% strain response (simple tension in a 50 V μm−1 electric field was obtained.

  10. Dielectric properties measurement system at cryogenic temperatures and microwave frequencies

    Energy Technology Data Exchange (ETDEWEB)