Double-peak polarization current response in the unusual SmA * phase of a fluorinated high-tilt antiferroelectric liquid crystal

2010 ◽  
Vol 89 (1) ◽  
pp. 16001 ◽  
Author(s):  
S. Ghosh ◽  
P. Nayek ◽  
S. K. Roy ◽  
T. Pal Majumder ◽  
M. Zurowska ◽  
...  
Keyword(s):  
Liquid Crystal ◽  
Current Response ◽  
Polarization Current ◽  
Double Peak

Chiral Liquid Crystal Trimer Exhibiting an Optically Uniaxial Smectic Phase with a Double-Peak Polarization

2012 ◽  
Vol 116 (15) ◽  
pp. 8678-8687 ◽  
Author(s):  
Daiki Tsuji ◽  
Yoichi Takanishi ◽  
Jun Yamamoto ◽  
Atsushi Yoshizawa
Keyword(s):  
Liquid Crystal ◽  
Smectic Phase ◽  
Double Peak ◽  
Chiral Liquid Crystal

Frequency dependence on polarization switching measurement in ferroelectric capacitors

2022 ◽  
Vol 43 (1) ◽  
pp. 014102
Author(s):  
Zhaomeng Gao ◽  
Shuxian Lyu ◽  
Hangbing Lyu
Keyword(s):  
Leakage Current ◽  
Time Lag ◽  
Hysteresis Loops ◽  
Polarization Switching ◽  
Wide Frequency Range ◽  
Switching Behavior ◽  
Current Response ◽  
Driving Frequency ◽  
Polarization Current ◽  
Rc Delay

Abstract Ferroelectric hysteresis loop measurement under high driving frequency generally faces great challenges. Parasitic factors in testing circuits such as leakage current and RC delay could result in abnormal hysteresis loops with erroneous remnant polarization (P r) and coercive field (E c). In this study, positive-up-negative-down (PUND) measurement under a wide frequency range was performed on a 10-nm thick Hf0.5Zr0.5O2 ferroelectric film. Detailed analysis on the leakage current and RC delay was conducted as the polarization switching occurs in the FE capacitor. After considering the time lag caused by RC delay, reasonable calibration of current response over the voltage pulse stimulus was employed in the integral of polarization current over time. In such a method, rational P–V loops measured at high frequencies (>1 MHz) was successfully achieved. This work provides a comprehensive understanding on the effect of parasitic factors on the polarization switching behavior of FE films.

scholarly journals Investigations of Current Generated in Construction of Polarization in Vectra A, Liquid Crystal Copolyester

2017 ◽  
Vol 6 (2) ◽  
pp. 55 ◽  
Author(s):  
Sapna Kalia ◽  
Rajesh Kalia
Keyword(s):  
Liquid Crystal ◽  
Low Temperature ◽  
Space Charge ◽  
Temperature Region ◽  
Dielectric Behavior ◽  
Polarization Current ◽  
Dipolar Relaxation ◽  
Composite Form ◽  
Higher Temperature

<div><p><em>The Thermally Stimulated Polarization Current (TSPC) is used to study the dielectric behavior of Vectra A, liquid crystal copolyester. The TSPC spectra of samples of Vectra A for various polarizing fields (3.8 kV/cm- 19.2 kV/cm) have been investigated. A dipolar relaxation is observed in the low temperature region ~ 30 <sup>o</sup>C due to orientation of naphthalene groups present in Vectra A which is termed as peak-P<sub>1</sub>. In the higher temperature region above 110 <sup>o</sup>C, the dipolar and space charge peaks are in composite form. TSPC cycle is performed to distinguish the dipolar and space charge peaks. Also, the TSPC spectra of annealed and doped samples of Vectra A are studied. The results obtained from TSPC spectra are compared with TSDC spectra of samples of Vectra A.</em>  </p></div>

scholarly journals INDUCTIVE SOURCE INDUCED POLARIZATION OF FROZEN ROCKS AND ITS RELATIONSHIP WITH DIELECTRIC RELAXATION OF ICE

2021 ◽  
Vol 2 (2) ◽  
pp. 67-73
Author(s):  
Nikolay O. Kozhevnikov
Keyword(s):  
Dielectric Relaxation ◽  
Decay Rate ◽  
Current Source ◽  
Induced Polarization ◽  
Voltage Source ◽  
Voltage Response ◽  
Current Response ◽  
Polarization Current ◽  
Polarization Voltage ◽  
Transient Electromagnetic

Fast decaying induced polarization in frozen rocks manifest itself as a not monotone induction transients. To account for induced polarization in the transient electromagnetic method, one usually uses the Pelton resistivity model. The relaxation time t, as found using the Pelton model, determines the decay rate of induced polarization voltage response to a current source. Conversion from t to the time constant t specifying the decay rate of the polarization current response to a voltage source, suggests that fast decaying induced polarization in frozen rocks is controlled by the dielectric relaxation of ice.

Electrochemical sensor based on incorporation of gold nanoparticles, ionic liquid crystal, and β-cyclodextrin into carbon paste composite for ultra-sensitive determination of norepinephrine in real samples

2019 ◽  
Vol 97 (12) ◽  
pp. 805-814
Author(s):  
Nada F. Atta ◽  
Ahmed Galal ◽  
Dalia M. El-Said
Keyword(s):  
Gold Nanoparticles ◽  
Ionic Liquid ◽  
Liquid Crystal ◽  
Electrochemical Sensor ◽  
Current Response ◽  
Carbon Paste ◽  
Great Ability ◽  
Real Samples ◽  
Sensitive Determination

A novel, reliable electrochemical sensor is fabricated for direct and sensitive determination of norepinephrine (NE) based on gold nanoparticles, ionic liquid crystal, and β-cyclodextrin modified carbon paste electrode, namely AuILCCDCPE. The ionic liquid crystal (ILC) played a key role in improving the current response of electro-oxidation of NE compared with other ionic liquids modified electrodes. The ILC increased the ionic conductivity of the paste and formed noncovalent interactions with both host (CD) and guest (NE) compounds. The solid state structure of the ILC helped in the formation of ordered films in the paste. Furthermore, CD and Au nanoparticles raised the stability and the electrocatalytic ability of the proposed sensor. Under optimized conditions, the fabricated electrochemical sensor showed a good electrochemical response towards NE in human urine in the linear dynamic ranges of 0.05–10 μmol/L and 20–300 μmol/L with a correlation coefficient of 0.999 and detection limit of 3.12 × 10−9 mol/L in the low concentration range. The practical analytical performance of the sensor was attained for determination of NE in real samples with satisfied recovery results. This sensor has great ability to be extended for electrochemical applications in assays of other drugs.

scholarly journals Efficient Electrochemical Sensor Based on Gold Nanoclusters/Carbon Ionic Liquid Crystal for Sensitive Determination of Neurotransmitters and Anti-Parkinson Drugs

2019 ◽  
Vol 10 (1) ◽  
pp. 46-55 ◽  
Author(s):  
Nada Farouk Atta ◽  
Ahmed Galal ◽  
Ekram Hamdy El-Ads ◽  
Aya Essam Galal
Keyword(s):  
Ionic Liquid ◽  
Liquid Crystal ◽  
Electrochemical Sensor ◽  
Gold Nanoclusters ◽  
Electrochemical Determination ◽  
Electrochemical Sensing ◽  
Current Response ◽  
Carbon Paste ◽  
Electro Catalytic Oxidation

Purpose: Herein we introduce a simple and sensitive sensor for the electrochemical determination of neurotransmitters compounds and anti-Parkinson drugs. Methods: The electrochemical sensor (Au/CILCE) based on gold nanoclusters modified carbon ionic liquid crystal (ILC) electrode was characterized using scanning electron microscopy and voltammetry measurements. Results: The effect of ionic liquid type in the carbon paste composite for the electro-catalytic oxidation of L-dopa was evaluated. Highest current response was obtained in case of ILC compared to other studied kinds of ionic liquids. The effective combination of gold nanoclusters and ILC resulted in extra advantages including large surface area and high ionic conductivity of the nanocomposite. L-dopa is considered one of the most important prescribed medicines for treating Parkinson’s disease. Moreover, a binary therapy using L-dopa and carbidopa proved effective and promising as it avoids the short comings of L-dopa mono-therapy for Parkinson’s patients. The Au/CILCE can detect L-dopa in human serum in the linear concentration range of 0.1 μM to 90 μM with detection and quantification limits of 4.5 nM and 15.0 nM, respectively. Also, the Au/CILCE sensor can simultaneously and sensitively detect L-dopa in the presence of carbidopa with low detection limits. Conclusion: The sensor is advantageous to be applicable for electrochemical sensing of other biologically electroactive species.

Freeze-fracture TEM of the helical smectic A* phase

1992 ◽  
Vol 50 (1) ◽  
pp. 278-279
Author(s):  
K.J. Ihn ◽  
R. Pindak ◽  
J. A. N. Zasadzinski
Keyword(s):  
Liquid Crystal ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Freeze Fracture ◽  
Smectic Phase ◽  
Layer Spacing ◽  
Screw Dislocations ◽  
Smectic A ◽  
Smectic Phases ◽  
Discrete Amount

A new liquid crystal (called the smectic-A* phase) that combines cholesteric twist and smectic layering was a surprise as smectic phases preclude twist distortions. However, the twist grain boundary (TGB) model of Renn and Lubensky predicted a defect-mediated smectic phase that incorporates cholesteric twist by a lattice of screw dislocations. The TGB model for the liquid crystal analog of the Abrikosov phase of superconductors consists of regularly spaced grain boundaries of screw dislocations, parallel to each other within the grain boundary, but rotated by a fixed angle with respect to adjacent grain boundaries. The dislocations divide the layers into blocks which rotate by a discrete amount, Δθ, given by the ratio of the layer spacing, d, to the distance between grain boundaries, lb; Δθ ≈ d/lb (Fig. 1).

Attractive mode force microscopy of chiral liquid crystal surfaces

1992 ◽  
Vol 50 (1) ◽  
pp. 268-269
Author(s):  
B.D. Terris ◽  
R. J. Twieg ◽  
C. Nguyen ◽  
G. Sigaud ◽  
H. T. Nguyen
Keyword(s):  
Liquid Crystal ◽  
Crystal Surfaces ◽  
Free Surfaces ◽  
Control Range ◽  
Force Microscopy ◽  
Liquid Crystal Films ◽  
Chiral Liquid Crystal ◽  
Crystal Films ◽  
Electrostatic Charging ◽  
And Shifts

We have used a force microscope in the attractive, or noncontact, mode to image a variety of surfaces. In this mode, the microscope tip is oscillated near its resonant frequency and shifts in this frequency due to changes in the surface-tip force gradient are detected. We have used this technique in a variety of applications to polymers, including electrostatic charging, phase separation of ionomer surfaces, and crazing of glassy films.Most recently, we have applied the force microscope to imaging the free surfaces of chiral liquid crystal films. The compounds used (Table 1) have been chosen for their polymorphic variety of fluid mesophases, all of which exist within the temperature control range of our force microscope.

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