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Characterization of Nematic Liquid Crystals at Microwave Frequencies

  • The use of nematic liquid crystal (LC) mixtures for microwave frequency applicationspresents a fundamental drawback: many of these mixtures have not been properly characterizedat these frequencies, and researchers do not have an a priori clear idea of which behavior they canexpect. This work is focused on developing a new procedure for the extraction of the main parametersof a nematic liquid crystal: dielectric permittivity and loss tangent at 11 GHz under differentpolarization voltages; splay elastic constantK11, which allows calculation of the threshold voltage(Vth); and rotational viscosityγ11, which allows calculating the response time of any arbitrary device.These properties will be calculated by using a resonator-based method, which is implementedwith a new topology of substrate integrated transmission line. The LC molecules should be rotated(polarized) by applying an electric field in order to extract the characteristic parameters; thus,the transmission line needs to have two conductors and low electric losses in order to preserve theintegrity of the measurements. This method was applied to a well-known liquid crystal mixture(GT3-23002 from MERCK) obtaining the permittivity and loss tangent versus bias voltage curves,the splay elastic constant, and the rotational viscosity of the mixture. The results validate the viabilityof the proposed method.

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Metadaten
Author:Vicente Nova, Carmen Bachiller, Belén Villacampa, Rainer Kronberger, Vicente E. Boria
URN:urn:nbn:de:hbz:832-epub4-16419
DOI:https://doi.org/10.3390/cryst10121106
ISSN:2073-4352
Parent Title (English):Crystals
Year of Completion:2020
Publisher:MDPI
Document Type:Article
Language:English
Date of first Publication:2020/12/03
Date of Publication (online):2021/05/07
GND-Keyword:Dielektrizitätszahl; Elastische Konstante; Mikrowelle; Nematische Phase
Tag:Loss tangent; Microwave; Nematic liquid crystal; Permittivity; Rotational viscosity; Splay elastic constant
Volume:10
Issue:12
Page Number:14
Institutes:Informations-, Medien- und Elektrotechnik (F07) / Fakultät 07 / Institut für Nachrichtentechnik
Dewey Decimal Classification:500 Naturwissenschaften und Mathematik
Open Access:Open Access
DeepGreen:DeepGreen
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International