Vishal Singh Chandel

Optical Studies of a Pure and Dye Doped Nematic Liquid Crystal E-24

The present paper reports the comparative optical behavior of a pure nematic mixture E-24 and its anthraquinone dye doped sample. The variation in the ordinary and extraordinary refractive index (no, ne) of the pure and dye doped samples with temperature has been discussed and it has been found that doped sample have a less refractive index compared to the pure sample. The variation in the order parameter for pure and doped samples with temperature has been discussed and it has been seen that the doped sample has a higher order parameter; the possible reasons have been discussed. The variations in birefringence and optical transmittance have also been presented here.

Investigation on multiferroic properties of BiFeO3 ceramics

BiFeO3 polycrystalline ceramics was prepared by solid-state reaction method and its structural, optical and magnetic properties were investigated. BiFeO3 was synthesized in a wide range of temperature (825–880 °C) and a well crystalline phase was obtained at a sintering temperature of 870 °C. X-ray diffraction patterns of the samples were recorded and analyzed for the confirmation of crystal structure and the determination of the lattice parameters. The average grain size of the samples was found to be between 1–2 μm. The determined value of direct bandgap of BiFeO3 ceramics was found to be 2.72 eV. The linear behavior of M-H curve at room temperature confirmed antiferromagetic properties of the BiFeO3 (BFO). S shaped M-H curve was obtained at a temperature of 5 K. In the whole temperature measurement range (5–300 K) of M-T, no anomalies were observed due to high Curie temperature and Neel temperature of the BiFeO3.

Lasing Characteristics of Dye-Doped Cholesteric Liquid Crystal

Cholesteric liquid crystals are one dimensional photonic band-gap materials due to their birefringence and periodic structure. Dye doped cholesteric liquid crystals are self-assembling, mirror-less, low threshold laser structures that exhibit distributed feedback. In this review paper, we have presented the development in the field of lasing characteristics of dye doped cholesteric liquid crystals.

Study of Dielectric Properties of Fenugreek Seeds (Trigonella Foenum Graecum)

Abstract The present paper studied the dielectric constant, dielectric loss, and ac conductivity of fenugreek seed, a medicinal seed (Trigonella foenum graecum), within the frequency range of 10 kHz and 10 MHz and the temperature range of 30°C and 50°C. Impedance gain/phase analyser (HP 4194 A) was used to measure the dielectric constant and the dielectric loss and Julabo (temperature controller, F-25, Germany) was used for keeping the temperature of fenugreek seeds constant. It was found that the dielectric constant and the dielectric loss decrease with the increase in the frequency while the same increase with the increase in temperature and moisture content. The ac conductivity increased with the increase in frequency, moisture and temperature.

Dielectric and spectroscopic analysis of cobalt doped potassium hexatitanate (K2Ti6O13) ceramics

Pure and cobalt doped (x = 0.05, 0.10, 0.15 mol %) polycrystalline potassium hexatitanate (K2Ti6O13) ceramics were synthesized using conventional solid state reaction route. XRD result confirmed the successful doping of Co in the K2Ti6O13 matrix, as no additional peak was observed in the pattern. Dielectric permittivity was found to decrease with the increase in frequency while it increased with the increase in doping. The dielectric loss decreased with small doping whereas excessive doping caused its augmentation. Ac conductivity (σac) has also been studied as a function of frequency at room temperature for all the samples. Scanning Electron Microscope (SEM) inspection of the synthesized samples showed the formation of rod like shapes. FTIR analysis was carried out to identify the chemical bonds present in the system.

Dielectric and Electro-Optical Properties of Ceramic Nanoparticles Doped Liquid Crystals

Copyright ©2016 KIEEME. All rights reserved. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0) which permits unrestricted noncommercial use, distribution, and reproduction in any medium, provided the original work is properly cited. pISSN: 1229-7607 eISSN: 2092-7592 DOI: http://dx.doi.org/10.4313/TEEM.2016.17.2.69 OAK Central: http://central.oak.go.kr TRANSACTIONS ON ELECTRICAL AND ELECTRONIC MATERIALS Vol. 17, No. 2, pp. 69-78, April 25, 2016

Low frequency dielectric relaxation and optical behaviour of a nematic liquid crystal 4-methyl n (2′-hydroxy, 4′-n-hexadecyloxy) azobenzene

Low frequency dielectric relaxation has been reported for a nematic liquid crystal in the frequency range of 1 kHz to 10 MHz and in the temperature range from 25 °C to 100 °C. The optical behaviour has also been studied by measuring the refractive indices, birefringence and optical transmittance in the temperature range mentioned above. The birefringence data have been used to calculate the order parameter by Vuks’ approach, and its variation with temperature has been discussed. Transition temperatures obtained using different techniques are found to be in good agreement with each other.

Dielectric study of important medicinal oil: Clove oil

Dielectric properties of clove oil were determined using an impedance gain phase analyzer (HP 4194 A) at discrete frequencies between 10 kHz and 3 MHz and a range of temperature between 25 °C and 45 °C. A micro processor controller based temperature controller (Julabo F-25) was used for keeping the temperature of clove oil constant. Dielectric constant of the sample is found to decrease with increase in frequency and temperature, while dielectric loss decreases with increase in frequency but increases with increase in temperature. Penetration depth has been calculated with the help of dielectric data and is found to decrease with increase in frequency.

Investigation of structural and magnetic properties of Pb free multiferroic (BiFeO3)1−x(BaTiO3)x solid solutions

A series of multiferroic (BiFeO3)1−x(BaTiO3)x [x = 0, 0.1, 0.2, 0.3]. ceramics were prepared to study the effect of combine substitution of BaTiO3 in (BiFeO3)1−x(BaTiO3)x. X-ray diffraction studies revealed phase transition from rhombohedral R3c to cubic on substitution of BaTiO3. XRD patterns of (BiFeO3)1−x(BaTiO3)x BF-BT. has been analyzed and single phase of rhombohedral was found up to 70 mol% of BiFeO3. Morphotropic phase boundary was found just above x=0.3, and finally it transformed into a cubic structure. The BF-BT ceramics exhibited symmetric magnetic hysteresis loops, indicating that they are magnetically ordered materials. Calculated values of remnant magnetizations of samples for x=0.1 and 0.2 indicated weak ferromagnetism in the samples.

Dielectric and Optical Study of Polymer Nematic Liquid Crystal Composite

The dielectric anisotropy and dispersion of the real and imaginary part of the permittivity of commercially important nematic mixture E-24 and its polymer composite were investigated in the frequency range from 1 kHz to 10 MHz, and temperature range 14℃ to 55℃. The percentage optical transmittance and density have also been measured for both the systems. The results have been explained by assuming molecular rotation about the long molecular axis, under a hindering nematic potential. The dielectric anisotropy Δe is positive, and the mean dielectric permittivity falls with rising temperature. Δe is also used to determine the order parameter with varying temperature.