The anomalous change of dielectric parameters in glassy films under illumination

Author(s):  
G.A. Bordovsky ◽  
V.A. Bordovsky ◽  
R.A. Castro
2015 ◽  
Vol 241 ◽  
pp. 226-236 ◽  
Author(s):  
Neha Solanki ◽  
Rajshree B. Jotania

Influence of Ca substitution on structural, magnetic and dielectric properties of Ba3Co2-xCaxFe24O41(where x = 0.0, 0.2, 0.4, 0.6, 0.8 and 1.0), prepared by Sol-Gel auto-combustion method, has been investigated in present studies. The obtained powder was sintered at 950 oC for 4 hrs. in the static air atmosphere. Structural analysis of Ca-doped Ba3Co2-xCaxFe24O41powders revealed pure Z-type hexaferrite phase at low temperature. The frequency dependent dielectric constant (Єʹ) and magnetic properties such as remanent magnetization (Mr), saturation magnetization (Ms) and coercivity (Hc) were studied. It is observed that coercivity increased gradually with increase in calcium content. The real dielectric constant (Єʹ) and dielectric loss tangent (tan δ) were studied in the frequency range of 20Hz to 2MHz. The dielectric parameters for all samples show normal dielectric behavior as observed in hexaferrites. Contents of Paper


Nanomaterials ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1886
Author(s):  
Yan Zhang ◽  
Bo-han Wu ◽  
Han-li Wang ◽  
Hao Wu ◽  
Yuan-cheng An ◽  
...  

Optically transparent polyimide (PI) films with good dielectric properties and long-term sustainability in atomic-oxygen (AO) environments have been highly desired as antenna substrates in low earth orbit (LEO) aerospace applications. However, PI substrates with low dielectric constant (low-Dk), low dielectric dissipation factor (low-Df) and high AO resistance have rarely been reported due to the difficulties in achieving both high AO survivability and good dielectric parameters simultaneously. In the present work, an intrinsically low-Dk and low-Df optically transparent PI film matrix, poly[4,4′-(hexafluoroisopropylidene)diphthalic anhydride-co-2,2-bis(4-(4-aminophenoxy)phenyl)hexafluoropropane] (6FPI) was combined with a nanocage trisilanolphenyl polyhedral oligomeric silsesquioxane (TSP-POSS) additive in order to afford novel organic–inorganic nanocomposite films with enhanced AO-resistant properties and reduced dielectric parameters. The derived 6FPI/POSS films exhibited the Dk and Df values as low as 2.52 and 0.006 at the frequency of 1 MHz, respectively. Meanwhile, the composite films showed good AO resistance with the erosion yield as low as 4.0 × 10−25 cm3/atom at the exposure flux of 4.02 × 1020 atom/cm2, which decreased by nearly one order of magnitude compared with the value of 3.0 × 10−24 cm3/atom of the standard PI-ref Kapton® film.


2004 ◽  
Vol 47 (4) ◽  
pp. 260-267 ◽  
Author(s):  
G. S. Bordonsky ◽  
A. O. Orlov ◽  
T. G. Filippova

1998 ◽  
Author(s):  
Zenoviy M. Mykytyuk ◽  
Michail Nutskovsky ◽  
L. Vernikova ◽  
A. Kotsyuba

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 605
Author(s):  
Ayushi Rastogi ◽  
Fanindra Pandey ◽  
Rajiv Manohar ◽  
Shri Singh

We report the effect of the doping of Cd1−xZnxS/ZnS core/shell quantum dots (CSQDs) in nematic liquid crystal p-methoxybenzylidenep-decylaniline (MBDA) at 0.05 wt/wt%, 0.1 wt/wt%, 0.15 wt/wt%, 0.2 wt/wt%, 0.25 wt/wt%, and 0.3 wt/wt% concentrations of CSQDs in MBDA. Dielectric parameters with and without bias with respect to frequency have been investigated. The change in electro-optical parameters with temperature has also been demonstrated. The increase in the mean dielectric permittivity was found due to the large dipole moment of CSQDs, which impose stronger interactions with the liquid crystal molecules. The dielectric anisotropy changes sign on doping CSQDs in MBDA liquid crystal. It was concluded that the CSQD doping noticeably increased the dielectric permittivity of nematic MBDA in the presence of an electric field. The doping of CSQDs in nematic MBDA liquid crystal reduced the ion screening effect effectively. This phenomenon is attributed to the competition between the generated ionic impurities during the assembling process and the ion trapping effect of the CSQDs. The rotational viscosity of nematic liquid crystal decreased with increasing concentration of the CSQDs, with a faster response time observed for the 0.05 wt/wt% concentration. The birefringence of the doped system increased with the inclusion of CSQDs in MBDA. These results find application in the field of display devices, phase shifters, LC – gratings, TIR waveguide, industries, and projectors.


2008 ◽  
Vol 22 (14) ◽  
pp. 2263-2273 ◽  
Author(s):  
RAJBIR SINGH ◽  
K. K. RAINA

Dielectric relaxation spectroscopy in the frequency range 50 Hz to 1 MHz has been carried out in a room temperature ferroelectric liquid crystal mixture in the SmC*, SmA and N* phases in cells of different thickness. The relaxation frequency fr, distribution parameter α and dielectric strength δ∊ have been evaluated. Goldstone mode, domain mode and soft mode have been observed. It is found that the cell thickness has a significant effect on the dielectric parameters of the ferroelectric liquid crystal material. The results have been discussed.


2020 ◽  
pp. 096739112096750
Author(s):  
Alper Kasgoz

In the present study, dielectric and microwave absorbing properties of barium titanate (BaTiO3) and strontium ferrite (SrFe12O19) filled thermoplastic polyurethane composites were investigated. The variations of the dielectric parameters of the BaTiO3 filled composite samples with filler concentration were also modeled and simulated by the power-law model to predict dielectric coefficients of the samples for higher filler concentrations. Comparing the prediction of the Power-law model and experimental measured dielectric values indicate that the Power-law model predicts dielectric parameters of the composite with acceptable accuracy. Microwave absorption analyses of the composite samples showed that SrFe12O19 is more effective than BaTiO3 on the enhancement of microwave absorption capability of TPU. The hybrid composite samples that contained both SrFe12O19 and BaTiO3 were also prepared, and their microwave absorption performance was evaluated. It was observed that much lower RL values than that of the composite samples, which were filled SrFe12O19 or BaTiO3 could be obtained by the hybrid composites. However, absorption bandwidth of them was narrower than counterparts that contained the same amount of SrFe12O19.


Sign in / Sign up

Export Citation Format

Share Document