scholarly journals Dielectric Spectroscopy Analysis of Liquid Crystals Recovered from End-of-Life Liquid Crystal Displays

Molecules ◽  
2021 ◽  
Vol 26 (10) ◽  
pp. 2873
Author(s):  
Ana Barrera ◽  
Corinne Binet ◽  
Frédéric Dubois ◽  
Pierre-Alexandre Hébert ◽  
Philippe Supiot ◽  
...  
Keyword(s):  
Liquid Crystals ◽  
End Of Life ◽  
Room Temperature ◽  
Liquid Crystal Displays ◽  
Dielectric Anisotropy ◽  
Frequency Range ◽  
Spectroscopy Analysis ◽  
Diamond Nanoparticles ◽  
Nematic Phases ◽  
Universal Law

In the present work, the dielectric properties of recycled liquid crystals (LCs) (non-purified, purified, and doped with diamond nanoparticles at 0.05, 0.1, and 0.2 wt%) were investigated. The studied LC mixtures were obtained from industrial recycling of end-of-life LC displays presenting mainly nematic phases. Dielectric measurements were carried out at room temperature on a frequency range from 0.1 to 106 Hz using an impedance analyzer. The amplitude of the oscillating voltage was fixed at 1 V using cells with homogeneous and homeotropic alignments. Results show that the dielectric anisotropy of all purified samples presents positive values and decreases after the addition of diamond nanoparticles to the LC mixtures. DC conductivity values were obtained by applying the universal law of dielectric response proposed by Jonscher. In addition, conductivity of the doped LC mixtures is lower than that of the undoped and non-purified LC.

Nematic Liquid Crystals with High Positive Dielectric Anisotropy

1979 ◽  
Vol 34 (8) ◽  
pp. 1092-1095 ◽  
Author(s):  
Maged A. Osman
Keyword(s):  
Liquid Crystals ◽  
Nematic Liquid Crystals ◽  
Dielectric Anisotropy ◽  
Formyl Group ◽  
Schiff’S Base ◽  
Strong Electron ◽  
Nematic Phases ◽  
Electron Donating Groups

Alkylamino- and formyl alkylamino-cyano Schiff's base, biphenyl and phenylbenzoate liquid crystals were synthesized. The mesomorphic behaviour of these compounds is described. The introduction of the formyl group in the higher homologues lead to the disappearance of the mesophase. The alkylamino and formylalkylamino substituents are strong electron donating groups and lead to nematic phases with remarkably high positive dielectric anisotropy

2,3,4-Trihydroxy benzonitrile-based liquid crystals: Fiber forming room temperature nematic phases

2020 ◽  
Vol 317 ◽  
pp. 114244 ◽  
Author(s):  
M.K. Srinatha ◽  
S. Poppe ◽  
G. Shanker ◽  
M. Alaasar ◽  
C. Tschierske
Keyword(s):  
Liquid Crystals ◽  
Room Temperature ◽  
Nematic Phases

scholarly journals Tunable microstrip liquid crystals patch antennas

2021 ◽  
Vol 1198 (1) ◽  
pp. 012010
Author(s):  
N A Romanov ◽  
T A Chimytov ◽  
A V Nomoev ◽  
E Ch Khartaeva ◽  
E A Gurvitz
Keyword(s):  
Dielectric Constant ◽  
Liquid Crystals ◽  
Magnetic Nanoparticles ◽  
Phase Shift ◽  
Patch Antenna ◽  
High Frequency ◽  
Dielectric Anisotropy ◽  
Slight Variation ◽  
Patch Antennas ◽  
Frequency Range

Abstract A patch antenna based on liquid crystals for the5G GHz range was simulated. The variation of the antenna frequency range after doping magnetic nanoparticles was verified. The high-frequency patch antenna parameters are calculated considering the dependence of the reflectivity of the antenna 11 on the dielectric anisotropy, gain, directivity and phase shift. The ability to control the frequency range of the patch antenna is shown. The phase distributions were demonstrated for 5CB crystals with a slight variation in the dielectric constant tensor and crystals with magnetic permeability.

scholarly journals Microstructure and electric response of Li,Sn co-doped NiO ceramics

2019 ◽  
Vol 13 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Jiecheng Zeng ◽  
Tusheng He ◽  
Yang Liu
Keyword(s):  
Grain Boundary ◽  
Polarization Effect ◽  
Room Temperature ◽  
Electric Response ◽  
Frequency Range ◽  
Spectroscopy Analysis ◽  
Frequency Independent ◽  
Increasing Temperature ◽  
Impedance Spectroscopy Analysis ◽  
Co Doped

Phase composition, microstructure and electric response of Li0.05SnxNi0.95 - xO (x = 0, 0.025, 0.05, 0.1) ceramics were systematically investigated. Colossal dielectric permittivity (>5000) is observed in the frequency range of 102-105 Hz at room temperature which becomes highly frequency-independent with increasing temperature. Secondary Sn-rich phase is detected in the grain boundary regions and it has a remarkable influence on the dielectric properties. Impedance spectroscopy analysis demonstrates that the microstructure is electrically heterogeneous, consisting of semiconducting grain and insulating grain boundary. Defect dipoles or polyvalent cations induced at high temperature may activate an electron hopping process under electric field, resulting in the enhancements of grain conductivity and polarization effect. This behaviour should be considered as the origin of the observed dielectric response.

scholarly journals Photothermal, Photoelectric, and Photothermoelectric Effects in Bi-Sb Thin Films in the Terahertz Frequency Range at Room Temperature

Photonics ◽  
2021 ◽  
Vol 8 (3) ◽  
pp. 76
Author(s):  
Mikhail K. Khodzitsky ◽  
Petr S. Demchenko ◽  
Dmitry V. Zykov ◽  
Anton D. Zaitsev ◽  
Elena S. Makarova ◽  
...  
Keyword(s):  
Thin Films ◽  
Terahertz Radiation ◽  
Room Temperature ◽  
Voltage Drop ◽  
Radiation Detection ◽  
Radiation Detectors ◽  
Thz Radiation ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range

The terahertz frequency range is promising for solving various practically important problems. However, for the terahertz technology development, there is still a problem with the lack of affordable and effective terahertz devices. One of the main tasks is to search for new materials with high sensitivity to terahertz radiation at room temperature. Bi1−xSbx thin films with various Sb concentrations seem to be suitable for such conditions. In this paper, the terahertz radiation influence onto the properties of thermoelectric Bi1−xSbx 200 nm films was investigated for the first time. The films were obtained by means of thermal evaporation in vacuum. They were affected by terahertz radiation at the frequency of 0.14 terahertz (THz) in the presence of thermal gradient, electric field or without these influences. The temporal dependencies of photoconductivity, temperature difference and voltage drop were measured. The obtained data demonstrate the possibility for practical use of Bi1−xSbx thin films for THz radiation detection. The results of our work promote the usage of these thermoelectric materials, as well as THz radiation detectors based on them, in various areas of modern THz photonics.

High Frequency Dielectric Response of the Ionic Liquid N-Methyl-N-ethylpyrrolidinium Dicyanamide

2007 ◽  
Vol 60 (1) ◽  
pp. 6 ◽  
Author(s):  
Simon Schrödle ◽  
Gary Annat ◽  
Douglas R. MacFarlane ◽  
Maria Forsyth ◽  
Richard Buchner ◽  
...  
Keyword(s):  
Ionic Liquid ◽  
Dielectric Loss ◽  
Dielectric Relaxation ◽  
High Frequency ◽  
Dielectric Response ◽  
Room Temperature ◽  
Room Temperature Ionic Liquid ◽  
Dielectric Relaxation Spectroscopy ◽  
Frequency Range ◽  
Fast Rotation

A study of the room-temperature ionic liquid N-methyl-N-ethylpyrrolidinium dicyanamide by dielectric relaxation spectroscopy over the frequency range 0.2 GHz ≤ ν ≤ 89 GHz has revealed that, in addition to the already known lower frequency processes, there is a broad featureless dielectric loss at higher frequencies. The latter is probably due to the translational (oscillatory) motions of the dipolar ions of the IL relative to each other, with additional contributions from their fast rotation.

scholarly journals Photoluminescence of CdSe/ZnS quantum dots in nematic liquid crystals in electric fields

2018 ◽  
Vol 9 ◽  
pp. 1544-1549 ◽  
Author(s):  
Margarita A Kurochkina ◽  
Elena A Konshina ◽  
Daria Khmelevskaia
Keyword(s):  
Quantum Dots ◽  
Liquid Crystals ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Electric Fields ◽  
Dielectric Anisotropy ◽  
Vertical Position ◽  
Decay Times ◽  
Pl Intensity

We have experimentally investigated the effect of the reorientation of a nematic liquid crystal (LC) in an electric field on the photoluminescence (PL) of CdSe/ZnS semiconductor quantum dots (QDs). To the LC with positive dielectric anisotropy, 1 wt % QDs with a core diameter of 5 nm was added. We compared the change of PL intensity and decay times of QDs in LC cells with initially planar or vertically orientated molecules, i.e., in active or passive LC matrices. The PL intensity of the QDs increases four-fold in the active LC matrix and only 1.6-fold in the passive LC matrix without reorientation of the LC molecules. With increasing electric field strength, the quenching of QDs luminescence occurred in the active LC matrix, while the PL intensity did not change in the passive LC matrix. The change in the decay time with increasing electric field strength was similar to the behavior of the PL intensity. The observed buildup in the QDs luminescence can be associated with the transfer of energy from LC molecules to QDs. In a confocal microscope, we observed the increase of particle size and the redistribution of particles in the active LC matrix with the change of the electric field strength. At the same time, no significant changes occurred in the passive LC matrix. With the reorientation of LC molecules from the planar in vertical position in the LC active matrix, quenching of QD luminescence and an increase of the ion current took place simultaneously. The obtained results are interesting for controlling the PL intensity of semiconductor QDs in liquid crystals by the application of electric fields.

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