scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985. An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice. The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

scholarly journals Dielectric Properties of Deep Ice Cores with Air-Hydrate Inclusions (Abstract)

1988 ◽  
Vol 10 ◽  
pp. 210-210
Author(s):  
Shinji Mae ◽  
Takeo Hondoh ◽  
Masayoshi Nakawo ◽  
C.C. Langway
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Dielectric Properties ◽  
Time Variation ◽  
Volume Fraction ◽  
Ice Cores ◽  
Frequency Range ◽  
Temperature Range ◽  
The Core

Air-hydrate inclusions have been found in deep ice cores from Dye 3, Greenland, which were taken in August 1981. Although the concentration of the air-hydrate crystals decreased with time, when the core was stored at a temperature of −50 °C, they still existed to an appreciable extent in 1985.An ice specimen was cut out from the Dye 3 core at a depth of 1500 m, where the volume fraction of the hydrate crystals was about 10−3 by volume. Its dielectric properties were measured in September 1985, in a frequency range of 30-20 × 103 Hz and temperature range of −20° to −90°C. The activation energy obtained for the relaxation time of the Debye dispersion was about 0.2 eV, which is much smaller than that of pure ice.The measurement was repeated once a month for about a year, and the sample was stored at a temperature of −10 °C between measurements. The time variation of the dielectric properties has been discussed in relation to the deterioration of the air-hydrate crystals.

Multilayer capacitors with bismuth copper tantalate dielectric fabricated in LTCC technology

2016 ◽  
Vol 33 (3) ◽  
pp. 118-123 ◽  
Author(s):  
Dorota Szwagierczak ◽  
Jan Kulawik ◽  
Beata Synkiewicz ◽  
Agata Skwarek
Keyword(s):  
Dielectric Properties ◽  
Grain Boundaries ◽  
Dielectric Response ◽  
Tape Casting ◽  
High Specific Capacitance ◽  
Frequency Range ◽  
Content Type ◽  
Temperature Range ◽  
New Material ◽  
Multilayer Capacitors

Purpose The work was aimed at preparation of green tapes based on a new material Bi2/3CuTa4O12, to achieve spontaneously formation of an internal barrier layer capacitor (IBLC), fabrication of multilayer elements using low temperature cofired ceramics (LTCC) technology and their characterization. Design/methodology/approach The study focused on tape casting, lamination and co-sintering procedures and dielectric properties of Bi2/3CuTa4O12 multilayer capacitors. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) studies of the ceramic elements were performed. Impedance spectroscopy was used for characterization of dielectric properties in the frequency range of 0.1 Hz to −2 MHz and in the temperature range from −55 to 400°C. DC conductivity was investigated in the temperature range 20 to 740°C. Findings SEM observations revealed a good compatibility of the applied commercial Pt paste with the ceramic layers. The EDS microanalysis showed a higher content of oxygen at grain boundaries. The dominant dielectric response, which was recorded in the low frequency range and at temperatures above 0°C, was attributed to grain boundaries. The dielectric response at low temperatures and/or high frequencies was related to grains. The fabricated multilayer capacitors based on Bi2/3CuTa4O12 exhibited a high specific capacitance. Originality/value A new material Bi2/3CuTa4O12 was applied for preparation of green ceramic tapes and utilized for fabrication of multilayer ceramic capacitors using the LTCC technology. This material belongs to the group of high permittivity nonferroelectric compounds with a complex perovskite structure of CaCu3Ti4O12, that causes the spontaneously formation of IBLCs.

Dielectric Analysis Of Semi-Crystalline Poly(Ethylene Terephthalate)

1994 ◽  
Vol 347 ◽  
Author(s):  
Jianghua Wei ◽  
Richard Delgado ◽  
Martin C. Hawley ◽  
Mark T.Demeuse
Keyword(s):  
Dielectric Properties ◽  
Ethylene Terephthalate ◽  
Dielectric Analysis ◽  
Frequency Range ◽  
Fixed Frequency ◽  
Scanning Calorimetry ◽  
Fixed Temperature ◽  
Temperature Range ◽  
Poly Ethylene Terephthalate ◽  
Poly Ethylene

ABSTRACTDielectric properties of poly(ethylene terephthalate) (PET) were measured over a frequency range of 10 KHz to 2.45 GHz and a temperature range of 20 to 110°C. Relaxation peaks were identified at 1) fixed frequency with variable temperatures, and 2) fixed temperature with variable frequencies. The crystallinity of poly (ethylene terephthalate) was measured using differential scanning calorimetry (DSC). Relationships between crystallinity, dielectric properties, and location of the dielectric relaxation peak on the frequency and temperature scales were studied for poly(ethylene terephthalate). Also, the dielectric loss factor decreases with increased crystallinity at 2.45 GHz and 4 GHz within the temperature range studied.

scholarly journals Dielectric Properties of Ternary ( ) ( )x ( ) x ZnO MgO PO 30 2 5 70− (x = 5, 8, 13) Glasses

2014 ◽  
Vol 5 (1) ◽  
Author(s):  
S. F. Khor ◽  
Z. A. Talib ◽  
W. M. Daud ◽  
H. A. A. Sidek ◽  
W. M. M. Yunus ◽  
...  
Keyword(s):  
Dielectric Properties ◽  
Dielectric Permittivity ◽  
Empirical Data ◽  
Loss Factor ◽  
Low Frequency ◽  
Frequency Range ◽  
Melt Quenching ◽  
Dipolar Relaxation ◽  
Temperature Range

(ZnO)30(MgO)x(P2O5)70-x glasses of the composition x = 5, 8 and 13 mol % have been prepared by melt quenching technique. The dielectric permittivity (89) and loss factor (8:) were measured in the frequency range from 0.01 Hz to 1 MHz and in the temperature range 303 to 573 K . From the results there are evidence of dipolar relaxation occurring between 103 – 106 Hz while at low frequency the spectrum is dominated by dc conduction which manifested by the 1/@ slope of loss factor plot. Value of the relaxing frequency (@p) plotted against 1/T shows one electrical transportation mechanism. The empirical data was sufficiently fitted by using Harviliak-Negami equation.

scholarly journals Dielectric and Conduction Processes and Behaviours in Ni0.3Zn0.7Fe2O4

2016 ◽  
Vol 846 ◽  
pp. 311-317
Author(s):  
Mohd Noor Mat ◽  
M.K. Halimah ◽  
Wan Mohd Daud Wan Yusoff ◽  
H. Mansor ◽  
H. Nizam ◽  
...  
Keyword(s):  
Activation Energy ◽  
Zinc Oxide ◽  
Iron Oxide ◽  
Dielectric Properties ◽  
Dielectric Relaxation ◽  
Relaxation Process ◽  
Peak Frequency ◽  
Frequency Range ◽  
Dielectric Relaxation Process ◽  
Frequency Relaxation

Dielectric relaxation and conductivity of Ni0.3Zn0.7Fe2O4 (NZF) were studied in the frequency range between 0.01 Hz to 3 MHz and temperature range within 313 K to 473 K. The sample was prepared by mixing Zinc Oxide, Nickel Oxide and Iron Oxide and sintered at 1573 K for 10 hours long. Dielectric properties were studied using Novo Control Dielectric Spectrometer. Dielectric relaxation and conductivity phenomena were discussed using an empirical model to key out the dielectric relaxation process. Analyze peak frequency relaxation process consist of four slopes to explain the dielectric relaxation process. The conductivity of the sample indicates an activated process and activation energy of dc conductivity is 0.44 ± 0.01 eV.

Application of Broad-Band Dielectric Spectroscopy for Investigations of Liquid Crystal - Porous Media Microcomposites

1997 ◽  
Vol 500 ◽  
Author(s):  
G. P. Sinha ◽  
B. Batalla ◽  
F. M. Aliev
Keyword(s):  
Dielectric Properties ◽  
Dielectric Spectroscopy ◽  
Volume Fraction ◽  
Broad Band ◽  
Interfacial Polarization ◽  
Pore Wall ◽  
Slow Process ◽  
Frequency Range ◽  
Average Pore ◽  
Hindered Rotation

ABSTRACTWe applied ultra broad-band dielectric spectroscopy in the frequency range from 10–3 Hz to 109 Hz to investigate the effect of size, shape and volume fraction of the pores in the porous matrices on the dielectric properties of liquid crystals (LC) dispersed in these matrices. Measurements in such a broad frequency range make it possible to obtain detailed information on the important aspects of the electrical behavior of heterogeneous materials such as: conductivity, surface polarization, and influence of confinement on dynamics of molecular motion of polar molecules forming LC. We investigated alkylcyanobiphenyls in the isotropie, nematic and smectic phases dispersed in porous glasses (average pore sizes - 100 Å and 1000 Å) which have randomly oriented, interconnected pores, and anopore membranes (pore diameters - 200 Å and 2000 Å) with parallel cylindrical pores. Dispersion of LC resulted in qualitative changes of their dielectric properties. Analysis of broad-band dielectric spectra shows that in organic (LC) - inorganic (porous matrix) heterogeneous composites conductivity plays an important role at F <1 Hz. We observe the appearance of new dielectric modes: a very slow process with characteristic frequency ≃ (1 – 10) Hz and a second process in frequency range about (103 - 106) Hz. The slow process arises due to the relaxation of interfacial polarization at pore wall - LC interface. The origin of this could be due to absorption of ions at the interface. Another possibility is the preferential orientation of the permanent dipoles at pore surface. The second new mode is due to the hindered rotation of the molecules near the interface. Additionally we observed two bulk like modes due to the rotation of the molecules around their short and long axii which are modified.

Dielectric Behaviour of Ice Microcrystals Dispersed within Suspensions: A DTC Study

1982 ◽  
Vol 37 (9) ◽  
pp. 1000-1004 ◽  
Author(s):  
P. Pissis ◽  
L. Apekis ◽  
C. Christodoulides ◽  
G. Boudouris
Keyword(s):  
Dielectric Properties ◽  
Relaxation Mechanism ◽  
Dielectric Behaviour ◽  
Frequency Range ◽  
Temperature Range ◽  
Dielectric Absorption

Abstract The dielectric properties of water-in-oil (W/O) suspensions have been studied by means of the depolarization thermocurrent (DTC) method in the temperature range of 85-250 K. Two predominant peaks have been observed at about 140 and 225 K. Evidence has been obtained that the peak at 140 K and the dielectric absorption observed by many investigators at sub-zero temperatures in the kHz frequency range are due to the same relaxation mechanism.

The absorption and dispersion of ultrasonic waves in acetic acid

1949 ◽  
Vol 199 (1056) ◽  
pp. 114-130 ◽  
Keyword(s):  
Activation Energy ◽  
Acetic Acid ◽  
Relaxation Time ◽  
Wave Length ◽  
Relaxation Mechanism ◽  
Ultrasonic Waves ◽  
Ultrasonic Vibrations ◽  
Frequency Range ◽  
Velocity Of Propagation ◽  
Absorption And Dispersion

The paper gives the results of measurements of the absorption and velocity of propagation of ultrasonic waves in acetic acid over the frequency range 0.5 to 67.5 Mc./sec. and at tem­peratures from 16 to 60° C. It is shown that a dispersion and a maximum in the value of absorption per wave-length occur, and the results confirm the existence of a relaxation pro­cess arising from the perturbation of a molecular equilibrium by the ultrasonic vibrations. The absorption coefficient, α , at a frequency, v , is represented by an equation of the form α = Bv 2 + Av 2 / 1 + ( v/v m ) 2 , where A, B and v m are parameters independent of v but varying with temperature, and v m is related to the relaxation time, r , by v m = 1/2 πr . These parameters are evaluated for a series of temperatures. The results are discussed in the light of existing theory, and in particular the activation energy of the process is obtained from the measured variation of relaxation time with temperature. It is suggested that the relaxation mechanism is possibly connected with a perturbation of the equilibrium between single and double molecules of acetic acid. The results also indicate the existence of a further relaxation process giving a second maximum in the absorption per wave-length at some frequency greater than 67·5 Mc./sec.

scholarly journals Dielectric Behaviour of Disperse Ice Microcrystals in The Frequency Range 105 to 10-2 Hz

1978 ◽  
Vol 20 (83) ◽  
pp. 359-365
Author(s):  
C. Lafargue ◽  
C. Bourgeois ◽  
G. Evrard
Keyword(s):  
Activation Energy ◽  
Dielectric Properties ◽  
Activation Energies ◽  
Dielectric Behaviour ◽  
Ageing Effect ◽  
Frequency Range ◽  
Low Frequencies

AbstractDielectric properties of ice microcrystals have been studied in the frequency range 3 x 105 to 10-2 Hz. Two separated dispersions are revealed : the Debye dispersion of ice and another dispersion at very low frequencies. Both dispersions present an ageing effect, with decreasing activation energy for the Debye dispersion and with increasing activation energy for the second one. It is shown in this paper that the sum of these activation energies retains a constant value of (1.05±0.02) eV.

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