DIELECTRIC PROPERTIES OF COMPLEX PEROVSKITE PZBT-PMNT CERAMIC UNDER COMPRESSIVE STRESS

2011 ◽  
Vol 25 (31) ◽  
pp. 2391-2398 ◽  
Author(s):  
MUANGJAI UNRUAN ◽  
TEERAWAT MONNOR ◽  
RATTIKORN YIMNIRUN ◽  
ORAWAN KHAMMAN ◽  
WANWILAI VITTAYAKORN ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Compressive Stress ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Polar Regions ◽  
Complex Perovskite ◽  
Compression Load ◽  
Stress Dependent

Effects of compressive stress on the dielectric properties of complex perovskite PZBT-PMNT ceramic were investigated. The dielectric properties measured under stress-free condition showed a composite nature with two distinct temperatures of dielectric maximum associated with PZBT and PMNT end members. The dielectric properties under the compressive stress were observed at stress levels up to 230 MPa using a home-built compressometer. The results clearly showed that the compression load significantly reduced both the dielectric constant and the dielectric loss tangent in every measuring frequency. The change of the dielectric constant with stress was attributed to competing influences of the intrinsic contribution of non-polar matrix and the extrinsic contributions of re-polarization and growth of micro-polar regions, while the clamping of the domain walls contributed to the stress-dependent changes of the dielectric loss tangent. Finally, a large drop of the dielectric constant after a stress cycle was likely caused by the stress induced decrease in switchable part of spontaneous polarization.

MEASUREMENT OF THE DIELECTRIC PROPERTIES OF LOW LOSS MATERIALS AT MILLIMETER WAVELENGTHS

1958 ◽  
Vol 36 (12) ◽  
pp. 1672-1677
Author(s):  
A. G. Mungall
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Brewster Angle ◽  
Angle Of Incidence ◽  
Low Loss ◽  
Millimeter Wavelengths ◽  
Space Technique

Measurement at millimeter wavelengths of the dielectric properties of low loss materials by a free space technique is described. The dielectric constant is determined from the Brewster angle, and the dielectric loss tangent from the attenuation coefficient measured at the Brewster angle of incidence. Results are given for bakelite at wavelengths between 5 and 10 mm. Details of the instrument, which was specifically designed for these measurements, are also given.

scholarly journals Investigation of the dielectric properties of copolymers based on 2,3,4,5,6-pentafluorostyrene, styrene, 4-fluoro-α-methylstyrene and α-methylstyrene

2019 ◽  
Vol 60 (12) ◽  
pp. 87-90
Author(s):  
Ignat S. Dolgin ◽  
◽  
Pyotr P. Purygin ◽  
Yury P. Zarubin ◽  
◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Signal Generator ◽  
Frequency Signal ◽  
Current Frequency ◽  
Dielectric Characteristics ◽  
Methyl Styrene

Three new copolymers based on fluorine-containing derivatives of styrene and α-methylstyrene were obtained. According to the results of the previous stages of the study, copolymers based on styrene derivatives have improved dielectric properties compared to polystyrene and a copolymer of styrene and α-methyl styrene. The dielectric constant ε and dielectric loss tangent tanδ were measured for the initial and synthesized samples of styrene – α-methyl styrene copolymer at Samara Electromechanical Plant OJ-SC (Samara city, Russia). All measurements of dielectric characteristics were carried out at an alternating current frequency of 10 GHz on a pressed copolymer tablet with a diameter of 10 and a thickness of 3 mm. During the experiment, a measuring stand was used, consisting of a high-frequency signal generator G4-83, an electronically counting frequency meter Ch3-54 with a frequency converter YaZCh-43, a measuring amplifier U2-4; low-frequency signal generator G3-109; measuring unit FKDG 418151.002. The results obtained indicate high values of the dielectric constant. For samples of copolymers of α-methylstyrene – 4-fluoro-α-methylstyrene and styrene – 4-fluoro-α-methylstyrene, values of 4.63 and 4.21, respectively, were obtained. These dielectric permittivity values are superior not only to samples previously obtained during the experiment, but also to some other compounds that are widely used in industry. In particular, the dielectric constant of lavsan, which is used in the manufacture of capacitors, is 3.1-3.3. The improved dielectric constant values are probably related to the high-quality composition of the copolymer. Samples of the copolymer containing 4-fluoro-α-methylstyrene are significantly superior to the copolymer with 2,3,4,5,6-pentafluorostyrene for this characteristic. The values of the dielectric loss tangent are in the range from 8.74∙10−4 to 37.4∙10−4. Given the dielectric characteristics of the synthesized copolymers, we can conclude that there are good prospects for the use of fluorine-containing styrene copolymers. The obtained values of permittivity and dielectric loss tangent indicate a good possible competitiveness of new materials based on new copolymers. In the future, it is planned to study a number of other physicochemical properties of these materials in order to obtain the most complete spectrum of their characteristics.

scholarly journals Studying the Effect of Titania Additions on some properties of Porcelain

2018 ◽  
Vol 28 (2) ◽  
pp. 169
Author(s):  
Abbas K. Saadon
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Titanium Oxide ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Raw Materials ◽  
X Ray Diffraction ◽  
X Ray ◽  
Manufacturing Method

The paper presents the production of porcelain for the ceramic by inexpensive natural raw materi-als, the principal raw materials of porcelain composition was selected consisting of 50% kaolin, 25% feldspar, 25% silica, the sample synthesized were characterize by X-ray diffraction (XRD) technique, than study the effect additives at different concentration form titanium oxide (𝑇𝑖𝑂2 )at (2, 5, 10, 15, 20) wt% on some physical and dielectric properties of porcelain. The samples are prepared by the conventional manufacturing method. The physical and dielectric properties of porcelain show that change considerably with the sub-stituent sample. It was found that the increase of the titanium oxide (𝑇𝑖𝑂2 ) additives of all our sample produce increasing in dielectric constant and bulk density, while decreasing with open porosity and dielectric loss tangent.

Spark Plasma Sintered AlN-BN Composites and its Dielectric Properties

2008 ◽  
Vol 368-372 ◽  
pp. 940-942
Author(s):  
Hai Yang Zhao ◽  
Wei Min Wang
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Sintering Temperature ◽  
Hexagonal Boron Nitride ◽  
Relative Dielectric Constant ◽  
Ceramic Composites ◽  
Spark Plasma

A series of samples of hexagonal boron nitride-aluminum nitride (10-90, 15-85, 20-80, 25-75, 30-70wt.%) ceramic composites were prepared by spark plasma sintering in a nitrogen atmosphere at 1650 °C-1800 °C for 5min. Different amounts of CaF2 were added as sintering aids. The effects of CaF2 and sintering temperature on densification and dielectric properties were discussed. The addition of CaF2 enhances relative dielectric constant and loss tangent of the samples. The increase in sintering temperature promotes the densification and decreases the dielectric loss tangent. When being sintered at 1700 °C, the relative density, dielectric constant and dielectric loss tangent of the sample with 15wt.%BN are 98.04%, 7.15 and 6.31×10-4 respectively.

scholarly journals Dielectric and electrical properties of Cr substituted Mg ferrites

2015 ◽  
Vol 39 (1) ◽  
pp. 1-12 ◽  
Author(s):  
AKM Zakaria ◽  
Faizun Nesa ◽  
MA Saeed Khan ◽  
SM Yunus ◽  
NI Khan ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Lattice Parameter ◽  
Activation Energies ◽  
X Ray Diffraction ◽  
Constant E ◽  
Cr Concentration ◽  
Academy Of Sciences

The spinel ferrites MgCrxFe2-xO4 (0.0 ? × ?1.0) were prepared through the solid state reaction using conventional ceramic method at 1300°C in air. The homogeneous phase of the ferrite samples was observed from the X-ray diffraction study. Lattice parameter of the samples was found to decrease with increasing Cr concentration in the system obeying Vegard’s law. The ac electrical resistivity, measured as a function of temperature, decreases with the increase of temperature indicating the semiconducting nature of all the samples. The activation energies were calculated and found to decrease with increasing Cr content. The lower activation energies are associated with higher electrical conductivity. With the increase of temperature, dielectric constant (e`) and dielectric loss tangent are observed to be increased; while with the increase of frequency, dielectric constant (e`) and dielectric loss tangent decrease for all the samples.Journal of Bangladesh Academy of Sciences, Vol. 39, No. 1, 1-12, 2015

scholarly journals Dielectric Behavior of Dysprosium Substituted Magnesium Ferrite

2018 ◽  
Vol 15 (1) ◽  
pp. 48-54
Author(s):  
Jeevan S. Ghodake
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Powder Diffraction ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Dielectric Behavior ◽  
Complex Dielectric Constant ◽  
Frequency Variation ◽  
Magnesium Ferrite ◽  
X Ray

Dysprosium substituted Magnesium ferrite weresuccessfully prepared by chemical combustion method. The as synthesized powder was presintered in air at 6000C for 1hr and finally sintered at 9500C for 1hr. From X-ray powder diffraction pattern of MgDy0.03Fe1.97O4, confirmed formation of single phase cubic spinel structure. The value of crystallite size obtained from X-ray powder diffraction (311) peak , it is found to be 46.38nm.The frequency and temperature variation of dielectric parameters such as real dielectric constant (ε′), complex dielectric constant (ε") and dielectric loss tangent (tanδ) were determined using Hioki LCR - Q meter. The frequency variation of dielectric constant shows a normal dielectric behavior of spinel ferrites. The dielectric loss tangent with frequency shows similar behavior as dielectric constant. The dielectric constant and dielectric loss tangent increases with increase in temperature

scholarly journals Dielectric properties of zinc sulfide concentrate during the roasting at microwave frequencies

2017 ◽  
Author(s):  
Guangjun He ◽  
Shiwei Li ◽  
Kun Yang ◽  
Jian Liu ◽  
Peng Liu ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Properties ◽  
Dielectric Loss ◽  
Zinc Sulfide ◽  
Apparent Density ◽  
Loss Tangent ◽  
Loss Factor ◽  
Microwave Energy ◽  
Dielectric Loss Factor ◽  
Sulfide Concentrate

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.

Studies on Metal Oxide Nanoparticle Doped PVP Polymer Nanocomposites

2021 ◽  
pp. 1153-1169
Author(s):  
Madhu B. J.
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Ac Conductivity ◽  
Stoichiometric Composition ◽  
Magnesium Nitrate ◽  
Solution Combustion ◽  
Mgo Nanoparticles ◽  
Metal Oxide Nanoparticle

Magnesium Oxide (MgO) nanoparticles have been synthesized by solution combustion technique using stoichiometric composition of magnesium nitrate as oxidizer and urea as fuel. Structure of the MgO was studied with the X-ray diffraction (XRD) using Cu-Kα radiation. MgO/polyvinylpyrrolidone (PVP) nanocomposites have been prepared by blending MgO nanoparticles with the polyvinylpyrrolidone. MgO/PVP nanocomposites were characterized by Fourier transform infrared (FTIR) spectroscopy. Frequency dependence of dielectric constant (ε′), dielectric loss tangent (tanδ) and AC conductivity studies have been undertaken on the MgO/PVP nanocomposites in the frequency range 50Hz-5MHz at room temperature. Dielectric properties such as dielectric constant (ε′) and dielectric loss tangent (tanδ) are found to decrease with the increase in the frequency. Further, AC conductivity of MgO/PVP nanocomposites was found to increase with an increase in the frequency. Observed variation in the a. c. conductivity with the frequency has been understood on the basis of electron hopping model.

Synthesis of new copolymers based on 2,3,4,5,6-pentafluorostyrene, styrene, α-methylstyrene and 4-fluoro-α-methylstyrene

2019 ◽  
Vol 60 (12) ◽  
pp. 91-95
Author(s):  
Ignat S. Dolgin ◽  
◽  
Pyotr P. Purygin ◽  
Yury P. Zarubin ◽  
◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Elevated Temperatures ◽  
Methylene Chloride ◽  
Research Work ◽  
Molar Ratio ◽  
Methyl Styrene ◽  
Derivatives Of

At the first stages of the research work, a copolymer of styrene and α methyl styrene was synthesized by the method of radical emulsion polymerization in an inert atmosphere of argon. The initiator was ammonium persulfate. The molar ratio of the initial monomers of styrene and α-methylstyrene was 70 : 30, respectively. It was found that copolymers synthesized under special controlled conditions have good values of permittivity and dielectric loss tangent. It should be noted that the choice of emulsifier directly affects the values of these indicators. It was previously shown that the most optimal emulsifier is potassium stearate, using which the best values of the dielectric constant and dielectric loss tangent were achieved. At the second stage of the research work, a number of copolymers were synthesized containing 4-methoxystyrene, 4 methyl styrene and α-methyl styrene in their structure. It was experimentally confirmed that the synthesis procedure may be applicable for the preparation of copolymers based on derivatives of styrene and α-methylstyrene. The resulting series of copolymers is highly soluble in methylene chloride; films of each copolymer sample of different thicknesses were obtained by casting from a solution. For this series of copolymer films, the dielectric constant and dielectric loss tangent were determined. It was found that the best values of permittivity and dielectric loss tangent are possessed by a sample of copolymer 4-methoxystyrene and α-methylstyrene. At the latest stage of the study, copolymers of styrene and 2,3,4,5,6-pentafluorostyrene, α-methylstyrene and 4-fluoro-α-methylstyrene, 2,3,4,5,6-pentafluorostyrene and 4-fluoro-α-methylstyrene were synthesized. These fluorine-containing derivatives of styrene and α-methylstyrene easily enough enter into the reaction of radical emulsion copolymerization. The copolymer yields are 53-76%, calculated on the weight of the starting monomers. The structure of a number of newly synthesized copolymers was confirmed by IR spectroscopy. In the future, it is planned to define the values of dielectric constant and dielectric loss tangent for these copolymer samples. It is planned to study the thermomechanical properties of the samples, since fluorine-containing polymers are a promising material for operation at elevated temperatures.

REVISIT TO DIELECTRIC PROPERTIES OF FERRITE CERAMICS

2012 ◽  
Vol 02 (03) ◽  
pp. 1230010 ◽  
Author(s):  
L. B. KONG ◽  
L. LIU ◽  
J. W. ZHAI ◽  
Z. W. LI ◽  
Z. H. YANG
Keyword(s):  
Dielectric Properties ◽  
Dielectric Loss ◽  
Loss Tangent ◽  
Dielectric Loss Tangent ◽  
Sintering Temperature ◽  
Short Review ◽  
Sintering Aids ◽  
Time Duration ◽  
Sintering Aid ◽  
Low Dielectric

Dielectric properties of ferrite ceramics have been less reported than their magnetic properties. Our recent study indicated that ferrite ceramics with very low dielectric loss tangent can be developed by using appropriate sintering aids, together with the optimization of other sintering parameters such as sintering temperature and time duration. Among various candidates of sintering aids, Bi 2 O 3 is the most promising one. It is important to find that the optimized concentration of sintering aid for full densification is not sufficient to achieve lowest dielectric loss tangent. This short review was aimed to summarize the understanding in microstructural evolution, grain growth, densification and dielectric properties of ferrite ceramics as a function of sintering aid concentration and sintering parameters, which could be used as a guidance to develop ferrite ceramics with low dielectric loss tangents for various applications.

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