scholarly journals Electrical Properties of Zn-Phthalocyanine and Poly (3-hexylthiophene) Doped Nematic Liquid Crystal

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Y. Karakuş ◽  
M. Okutan ◽  
A. Kösemen ◽  
S. E. San ◽  
Z. Alpaslan ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Liquid Crystal ◽  
Electrical Properties ◽  
Impedance Spectroscopy ◽  
Absorption Coefficient ◽  
Nematic Liquid Crystal ◽  
Critical Frequency ◽  
Relaxation Times ◽  
Zinc Phthalocyanine ◽  
Absorption Coefficients

An E7 coded nematic liquid crystal was doped with zinc phthalocyanine and poly (3-hexylthiophene). A variety of properties including relaxation time, absorption coefficient, and critical frequency of this doped system were investigated using impedance spectroscopy. The doped systems displayed increased absorption coefficients in the range 0.22–0.55 and relaxation times from5.05×10−7 s to3.59×10−6 s with a decrease in the critical frequency from 3.54 MHz to 2.048 MHz.

The Electrically Controlled Birefringence Measurement Influence of Liquid Crystal Caused by Absorption Effect in Infrared Region

2014 ◽  
Vol 875-877 ◽  
pp. 467-471
Author(s):  
Ning Wang ◽  
Xiao Xia Li
Keyword(s):  
Liquid Crystal ◽  
Absorption Coefficient ◽  
Approximate Method ◽  
Nematic Liquid Crystal ◽  
Infrared Region ◽  
Interference Method ◽  
Absorption Coefficients ◽  
Absorption Effect ◽  
Ordinary Light

The electrically controlled birefringence of nematic liquid crystal BL-009 was measured by polarized interference method. The influence of LC absorption effect, the birefringence variation, is discussed in this paper. The experiments results showed the influence to birefringence is big in infrared region. Not only the birefringence value is greatly different with that of unconsidering absorption effect, but also the gradient changing of birefringence curves is obvious. Furthermore, the electrically controlled birefringences of two conditions are compared when the absorption coefficients of ordinary light and the extraordinary light are nearly same and greatly different. The analysis demonstrated the approximate method of absorption coefficient is feasible.

scholarly journals Dynamic behavior of a nematic liquid crystal with added carbon nanotubes in an electric field

2018 ◽  
Vol 9 ◽  
pp. 233-241 ◽  
Author(s):  
Emil Petrescu ◽  
Cristina Cirtoaje
Keyword(s):  
Carbon Nanotubes ◽  
Relaxation Time ◽  
Liquid Crystal ◽  
Electric Field ◽  
Dynamic Behavior ◽  
Nematic Liquid Crystal ◽  
Relaxation Times ◽  
Continuum Theory ◽  
Pure Liquid ◽  
Significant Difference

The dynamic behavior of a nematic liquid crystal with added carbon nanotubes (CNTs) in an electric field was analyzed. A theoretical model based on elastic continuum theory was developed and the relaxation times of nematic liquid crystals with CNTs were evaluated. Experiments made with single-walled carbon nanotubes dispersed in nematic 4-cyano-4’-pentylbiphenyl (5CB) indicated a significant difference of the relaxation time when compared to pure liquid crystal. We also noticed that the relaxation time when the field is switched off depends on how long the field was applied. It is shorter when the field is switched off immediately after application and longer when the field was applied for at least one hour.

scholarly journals The Dynamic Properties of 5Cb Filled with Aerosil Particles Investigated by Pcs

1999 ◽  
Vol 559 ◽  
Author(s):  
F.M. Aliev ◽  
M. Kreuzer ◽  
Yu.P. Panarin
Keyword(s):  
Liquid Crystal ◽  
Temperature Dependence ◽  
Relaxation Process ◽  
Nematic Liquid Crystal ◽  
Broad Spectrum ◽  
Dynamic Properties ◽  
Relaxation Times ◽  
Correlation Spectroscopy ◽  
Relaxation Processes ◽  
Optoelectronic Application

ABSTRACTNematic liquid crystal filled with Aerosil particles, a prospective composite material for optoelectronic application, has been investigated by static light scattering and Photon Correlation Spectroscopy (PCS). The Aerosil particles in filled nematic liquid crystals (FN) form a network structure with LC domains about 2500 Å in size with a random distribution of the director orientation of each domain.We found that the properties of 5CB are considerably affected by the network. The N-I phase transition in filled 5CB was found to be smeared out and depressed. PCS experiments show that two new relaxation processes appear in filled 5CB in addition to the director fluctuation process in bulk. The slow relaxation process, with a broad spectrum of relaxation times, is somewhat similar to the slow decay, which is observed in confined nematic liquid crystal.The middle frequency process was assigned to the director fluctuations in the surface layer formed at the particle-LC interface. The decay function describing this relaxation process is a stretched exponential (β ≍ 0.7). The temperature dependence of the relaxation times of the middle frequency obeys the Vogel-Rilcher law. Such a temperature dependence, accompanied by a broad spectrum of relaxation times suggests that the dynamics of the director fluctuations near the Aerosil particle-LC interface is glass-like.

Optical measurement of the director relaxation time in a periodically reoriented nematic liquid crystal

1999 ◽  
Vol 86 (6) ◽  
pp. 3042-3047 ◽  
Author(s):  
P. L. Papadopoulos ◽  
H. M. Zenginoglou ◽  
J. A. Kosmopoulos
Keyword(s):  
Relaxation Time ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Optical Measurement

scholarly journals Measurements of the Electrical Properties of Ice Ih Single Crystals by Admittance and Thermally Stimulated Depolarization Techniques

1978 ◽  
Vol 21 (85) ◽  
pp. 219-230 ◽  
Author(s):  
Arturo Loria ◽  
Ezio Mazzega ◽  
Umberto del Pennino ◽  
Giovanni Andreotti
Keyword(s):  
Activation Energy ◽  
Relaxation Time ◽  
Electrical Properties ◽  
Single Crystals ◽  
Relaxation Spectrum ◽  
Relaxation Times ◽  
Dielectric Strength ◽  
Inert Gas ◽  
Complex Admittance ◽  
Thermally Stimulated Depolarization

Abstract Ice Ih single crystals were investigated by complex admittance and thermally stimulated depolarization (TSD) techniques, in the relaxation-time ranges 10–5–10 s and 10–104 s respectively. The relaxation spectrum was resolved and three components of it were studied. Second-order kinetics had to be assumed for two of the TSD spectra to obtain Arrhenius-type relaxation times. The “Debye spectrum” had an activation energy for the relaxation time of 0.64 eV at the high temperatures and its dielectric strength revealed a possible defect cross-over at T c = 190 K. Far below this temperature the activation energy was 0.38 eV, that is about half of that necessary for a pair of ion defects to form. In comparison with the results of other authors, a lower concentration of ionic defects, or possibly of Bjerrum–ion aggregates, was deduced to occur in our crystals. Inert-gas host molecules were proposed as a possible origin of the two other spectra, having relaxation times shorter than the “Debye spectrum” and energies of 0.33 eV and 0.37 eV. Moreover the 0.33 eV spectrum, whose dielectric strength appears at a temperature below T c, might alternatively be related to the cross-over of the “Debye spectrum”.

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