The influence of suspended nanoparticles on the Frederiks threshold of the nematic host

In recent years, several papers reported an enhanced dielectric anisotropy when ferroelectric particles were suspended in a liquid crystal. These results seem to be sensitive to the liquid crystal used and the preparation method of the ferroelectric particles. In this paper, we compare different preparation methods of suspended barium titanate in two different liquid crystal hosts. As a control experiment, we followed similar preparation steps with non-ferroelectric silica particles. In all cases, we found a broadening of the optical Frederiks transition but no change in the dielectric anisotropy. Raman spectroscopy has been used to investigate the loss of tetragonal structure in the barium titanate as a function of milling time and particle size. As reported in the earlier literature, barium titanate does not exhibit a well-defined tetragonal crystal structure below a certain particle size and loses its ferroelectric features. This provides a simple rationalization for the absence of any dielectric enhancement.

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Nano-sized barium titanate powders with tetragonal crystal structure prepared by flame spray pyrolysis

Journal of the European Ceramic Society ◽

10.1016/j.jeurceramsoc.2007.05.018 ◽

2008 ◽

Vol 28 (1) ◽

pp. 109-115 ◽

Cited By ~ 17

Author(s):

D.S. Jung ◽

S.K. Hong ◽

J.S. Cho ◽

Y.C. Kang

Keyword(s):

Crystal Structure ◽

Barium Titanate ◽

Spray Pyrolysis ◽

Flame Spray Pyrolysis ◽

Flame Spray ◽

Tetragonal Crystal ◽

Tetragonal Crystal Structure

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Effect of Particle Size on Electro-Optic Properties of Liquid Crystal Devices Doped with γ-Cyclodextrin Stabilized Barium Titanate Nanoparticles

Molecular Crystals and Liquid Crystals ◽

10.1080/15421406.2015.1028000 ◽

2015 ◽

Vol 611 (1) ◽

pp. 100-108 ◽

Cited By ~ 1

Author(s):

Yukihide Shiraishi ◽

Ryouma Tsujihata ◽

Hiroya Sawai ◽

Shunsuke Kobayashi ◽

Naoki Toshima

Keyword(s):

Particle Size ◽

Liquid Crystal ◽

Barium Titanate ◽

Liquid Crystal Devices ◽

Electro Optic ◽

Effect Of Particle Size ◽

Barium Titanate Nanoparticles

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Rietveld refinement on XRD and TEM study of nanocrystalline PbZr0:5Ti0:5O3 ceramics prepared with a soft chemistry route

Materials Science-Poland ◽

10.1515/msp-2015-0040 ◽

2015 ◽

Vol 33 (1) ◽

pp. 18-24 ◽

Cited By ~ 1

Author(s):

T.K. Mandal

Keyword(s):

Particle Size ◽

Rietveld Refinement ◽

Average Particle Size ◽

Average Diameter ◽

Average Particle ◽

Soft Chemistry ◽

Hexagonal Symmetry ◽

Tetragonal Crystal ◽

Tetragonal Crystal Structure ◽

Bet Method

AbstractPbZr0:5Ti0:5O3 nanopowders (~27 nm) have been prepared by a controlled reconstructive thermal decomposition and crystallization from an amorphous polymeric precursor with polyvinyl alcohol (PVA) and sucrose at 400 to 700 °C in air. The Rietveld refinement of the XRD profiles which were recorded at room temperature for the PbZr0:5Ti0:5O3 powder prepared by a thermal treatment at 700 °C for 2 h, confirmed the P4mm tetragonal crystal structure of the as prepared PbZr0:5Ti0:5O3 nanopowders, with a = 0.4036 nm and c = 0.4147 nm. A hexagonal symmetry (R3c), with a = 0.5774 nm and c = 1.4212 nm, was also detected from Rietveld refinement analysis. Thus, tetragonal and hexagonal phases were found to coexist with the as prepared PbZr0:5Ti0:5O3 nanopowders. The average particle size (D) of the PbZr0:5Ti0:5O3 powders, estimated with the help of the specific surface area, measured by BET method, was 26.1 nm. Average D value, calculated by D2θ1/2 in the XRD peaks with the Debye-Scherrer relation was ~24 nm. TEM study made it possible to measure the particle size of PbZr0:5Ti0:5O3 powders with an average diameter of 27 nm.

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Drastic improvement of Curie temperature by chemical pressure in N-type diluted magnetic semiconductor Ba(Zn,Co)$$_{2}$$As$$_{2}$$

Scientific Reports ◽

10.1038/s41598-021-86205-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Licheng Fu ◽

Yilun Gu ◽

Guoxiang Zhi ◽

Haojie Zhang ◽

Rufei Zhang ◽

...

Keyword(s):

Unit Cell Volume ◽

Diluted Magnetic Semiconductor ◽

Magnetic Semiconductor ◽

Vital Role ◽

Ferromagnetic Transition ◽

Chemical Pressure ◽

Tetragonal Crystal ◽

Tetragonal Crystal Structure ◽

Diluted Magnetic ◽

Ferromagnetic Ordering

AbstractWe report the effect of chemical pressure on the ferromagnetic ordering of the recently reported n-type diluted magnetic semiconductor Ba(Zn$$_{1-x}$$ 1 - x Co$$_{x}$$ x )$$_{2}$$ 2 As$$_{2}$$ 2 which has a maximum $$T_C$$ T C $$\sim$$ ∼ 45 K. Doping Sb into As-site and Sr into Ba-site induces negative and positive chemical pressure, respectively. While conserving the tetragonal crystal structure and n-type carriers, the unit cell volume shrink by $$\sim$$ ∼ 0.3$$\%$$ % with 15$$\%$$ % Sr doping, but drastically increase the ferromagnetic transition temperature by 18$$\%$$ % to 53 K. Our experiment unequivocally demonstrate that the parameters of Zn(Co)As$$_{4}$$ 4 tetrahedra play a vital role in the formation of ferromagnetic ordering in the Ba(Zn,Co)$$_{2}$$ 2 As$$_{2}$$ 2 DMS.

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Signal Amplification in an Optical and Dielectric Biosensor Employing Liquid Crystal-Photopolymer Composite as the Sensing Medium

Biosensors ◽

10.3390/bios11030081 ◽

2021 ◽

Vol 11 (3) ◽

pp. 81

Author(s):

Hassanein Shaban ◽

Shih-Chun Yen ◽

Mon-Juan Lee ◽

Wei Lee

Keyword(s):

Dielectric Constant ◽

Liquid Crystal ◽

Uv Irradiation ◽

Signal Amplification ◽

Limit Of Detection ◽

Optical Signal ◽

Uv Exposure ◽

Dielectric Anisotropy ◽

Optical Texture ◽

Potential Development

An optical and dielectric biosensor based on a liquid crystal (LC)–photopolymer composite was established in this study for the detection and quantitation of bovine serum albumin (BSA). When the nematic LC E7 was doped with 4-wt.% NOA65, a photo-curable prepolymer, and photopolymerized by UV irradiation at 20 mW/cm2 for 300 s, the limit of detection determined by image analysis of the LC optical texture and dielectric spectroscopic measurements was 3400 and 88 pg/mL for BSA, respectively, which were lower than those detected with E7 alone (10 μg/mL BSA). The photopolymerized NOA65, but not the prepolymer prior to UV exposure, contributed to the enhanced optical signal, and UV irradiation of pristine E7 in the absence of NOA65 had no effect on the optical texture. The effective tilt angle θ, calculated from the real-part dielectric constant ε’, decreased with increasing BSA concentration, providing strong evidence for the correlation of photopolymerized NOA65 to the intensified disruption in the vertically oriented LC molecules to enhance the optical and dielectric signals of BSA. The optical and dielectric anisotropy of LCs and the photo-curable dopant facilitate novel quantitative and signal amplification approaches to potential development of LC-based biosensors.

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Effect of temperature, time and particle size of Ti precursor on hydrothermal synthesis of barium titanate

Materials Science and Engineering B ◽

10.1016/j.mseb.2008.06.018 ◽

2008 ◽

Vol 152 (1-3) ◽

pp. 60-65 ◽

Cited By ~ 17

Author(s):

A. Habib ◽

R. Haubner ◽

N. Stelzer

Keyword(s):

Particle Size ◽

Hydrothermal Synthesis ◽

Barium Titanate ◽

Effect Of Temperature ◽

Temperature Time ◽

Synthesis Of Barium Titanate

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Effect of Doping ofCd1−xZnxS/ZnS Core/Shell Quantum Dots in Negative Dielectric Anisotropy Nematic Liquid Crystal p-Methoxybenzylidene p-Decylaniline

Crystals ◽

10.3390/cryst11060605 ◽

2021 ◽

Vol 11 (6) ◽

pp. 605

Author(s):

Ayushi Rastogi ◽

Fanindra Pandey ◽

Rajiv Manohar ◽

Shri Singh

Keyword(s):

Quantum Dots ◽

Liquid Crystal ◽

Dielectric Permittivity ◽

Nematic Liquid Crystal ◽

Phase Shifters ◽

Ion Trapping ◽

Dielectric Anisotropy ◽

Core Shell ◽

Optical Parameters ◽

Dielectric Parameters

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.

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