Large increase of the low-frequency dielectric constant of gallium sulfide under hydrostatic pressure

1994 ◽  
Vol 49 (7) ◽  
pp. 4601-4604 ◽  
Author(s):  
A. Segura ◽  
A. Chevy
Keyword(s):  
Dielectric Constant ◽  
Hydrostatic Pressure ◽  
Low Frequency ◽  
Gallium Sulfide

scholarly journals The effects of additive on microstructure and electrical properties of batio3 ceramics

2004 ◽  
Vol 1 (3) ◽  
pp. 89-98 ◽  
Author(s):  
Vesna Paunovic ◽  
Ljiljana Zivkovic ◽  
Ljubomir Vracar ◽  
Vojislav Mitic ◽  
Miroslav Miljkovic
Keyword(s):  
Dielectric Constant ◽  
Curie Temperature ◽  
Room Temperature ◽  
Low Frequency ◽  
Dissipation Factor ◽  
The Other ◽  
Uniform Microstructure ◽  
Average Grain Size ◽  
Solid State Sintering ◽  
Curie Temperatures

In this paper comparative investigations of microstructure and dielectric properties of BaTiO3 ceramics doped with 1.0 wt% of Nb2O5, MnCO3 and CaZrO3 have been done. BaTiO3 samples were prepared using conventional method of solid state sintering at 13000C for two hours. Two distinguish micro structural regions can be observed in sample doped with Nb2O5. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO3 and CaZrO3 doped ceramics the uniform microstructure is formed with average grain size about 0.5- 2?m and 3-5?m respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO3/BaTiO3. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f = 6kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a Curie- Weiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO3, was observed in all investigated samples.

Volume dependence of the electronic dielectric constant of crystals under hydrostatic pressure

1978 ◽  
Vol 18 (12) ◽  
pp. 7186-7188 ◽  
Author(s):  
Jai Shanker ◽  
A. K. G. Lashkari ◽  
O. P. Sharma
Keyword(s):  
Dielectric Constant ◽  
Hydrostatic Pressure ◽  
Volume Dependence

Soft-Mode Phonons in SrTiO3 Thin Films Studied by Far-Infrared Ellipsometry and Raman Scattering

1999 ◽  
Vol 603 ◽  
Author(s):  
A. A. Sirenko ◽  
C. Bernhard ◽  
A. Golnik ◽  
I. A. Akimov ◽  
A. M. Clark ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Raman Scattering ◽  
Soft Mode ◽  
Experimental Studies ◽  
Low Frequency ◽  
Pulsed Laser ◽  
Far Infrared ◽  
Laser Deposition ◽  
Bulk Crystals ◽  
Infrared Ellipsometry

AbstractWe report the experimental studies of the vibrational spectra of SrTiO3 films with the thickness of 1 µm grown by pulsed laser deposition. Fourier-transform infrared ellipsometry between 30 and 700 cm−1 and electric field-induced Raman scattering have been utilized for investigation of the phonon behavior. These results can be used for comparison with the low-frequency measurements of the static dielectric constant. In the films, the soft mode reveals hardening compared to that in bulk crystals. This observation is in agreement with the Lyddane-Sachs-Teller formalism.

Enhancement on the Electrical Properties of PVDF/MgO Nanocomposite Thin Films

2015 ◽  
Vol 1134 ◽  
pp. 16-22
Author(s):  
Adillah Nurashikin Arshad ◽  
Rozana Mohd Dahan ◽  
Mohamad Hafiz Mohd Wahid ◽  
Muhamad Naiman Sarip ◽  
Mohamad Rusop Mahmood
Keyword(s):  
Thin Films ◽  
Dielectric Constant ◽  
Low Frequency ◽  
Annealed Sample ◽  
High Resistivity ◽  
Tangent Loss ◽  
Annealing Temperatures ◽  
Metal Insulator Metal ◽  
Nanocomposite Thin Films ◽  
Tan Δ

Poly (vinylideneflouride)/nanomagnesium oxide (PVDF/MgO) film with MgO loading percentage of 7% were annealed with various annealing temperatures ranging from 70°C to 170°C. The PVDF/MgO(7%) thin films were fabricated using spin coating technique with metal-insulator-metal (MIM) configuration and the dielectric constant of PVDF/MgO(7%) with respect to annealing temperatures was studied. The PVDF/MgO nanocomposite thin films annealed at temperature of 70°C (AN70) showed an improvement in the dielectric constant of 27 at 103 Hz compared to un-annealed sample (UN), which is 21 at the same frequency. As the annealing temperatures were increased from 90°C (AN90) to 150oC (AN150), the dielectric constant of PVDF/MgO(7%) were found to gradually decreased from 25 to 12 respectively, interestingly lower than the UN thin films. AN70 also produced low value of tangent loss (tan δ) at frequency of 103 Hz. The resistivity value of AN70 was also found to increase from 3.08×104Ω.cm (UN-PVDF) to 1.05×105Ω.cm. The increased in dielectric constant, with low tangent loss and high resistivity value suggests that 70°C was the favourable annealing temperature for PVDF/MgO(7%) for application in electronic devices such as low frequency capacitor.

Low-frequency dielectric dispersion and microwave dielectric properties of dry and water-saturated limestones of Jodhpur region

Geophysics ◽  
2006 ◽  
Vol 71 (5) ◽  
pp. G269-G277 ◽  
Author(s):  
R. J. Sengwa ◽  
A. Soni
Keyword(s):  
Dielectric Constant ◽  
Chemical Composition ◽  
Bulk Density ◽  
Low Frequency ◽  
Dielectric Dispersion ◽  
Complex Dielectric Constant ◽  
Frequency Limit ◽  
Microwave Dielectric ◽  
Limestone Sample ◽  
Water Saturated

We investigated the complex dielectric constant of 17 different grades of dry and water-saturated limestone samples from the Jodhpur region in the frequency range of [Formula: see text] to [Formula: see text] and also at [Formula: see text] at room temperature. The Cole-Cole dielectric dispersion model was used to compute the values of low-frequency-limit dielectric constant, high-frequency-limit dielectric constant, dielectric strength, and principal value of the relaxation time for each dry limestone sample. The chemical composition, sample bulk density, and porosity of each sample studied were determined to learn which of these factors govern their dielectric parameters. Analysis of the low-frequency dielectric constant confirms that chemical composition and bulk density are the ma-jor factors governing the dielectric constant values; but for water-saturated samples, the frequency-dependent dielectric constant values are also sensitive to porosity and grain size. The ac conductivity of all of the dry samples increases with the increase in frequency from [Formula: see text] to [Formula: see text], but water-saturated samples have comparatively high conductivity; some samples have values independent of the frequency. The microwave dielectric constant of dry samples depends mainly on the amount of the constituents of the oxide, their chemical composition, and sample bulk density. The contribution of the measured dielectric-constant values of each oxide present in the sample is identified by using their density-reduced values of the dielectric constant. The porosity-dependent mixing equations for solid and fluid components of the system were also found suitable for determining the dielectric constant of water-saturated limestone samples at microwave frequency.

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