Magneto-dielectric Relaxation Behaviors of E7 Nematic Liquid Crystal

• Main Authors: Chih-Wei Tseng, 曾致維
• Other Authors: Chi-Kuen Lo
• Format: Others
• Language: zh-TW
• Published: 2011
• Online Access: http://ndltd.ncl.edu.tw/handle/81845704671061350157

碩士 === 國立臺灣師範大學 === 物理學系 === 99 === Liquid crystal has been well known as an electro-optical material because of its favorable properties. Most of the studies focused on improving its electro-optical properties, such as response time, driving voltage, etc. The magneto-dielectric relaxation behaviors have not yet been well clarified. Therefore, in this thesis, we study these interesting properties of E7 liquid crystal using dielectric spectroscopy method. The dielectric spectra are measured by an LCR meter (Agilent E4980A) in the frequency of 20 to 2 MHz. In the course of measuring, a magnetic field is applied perpendicular to sample surface. The dynamic behaviors of liquid crystal molecular under magnetic field are discussed. Under constant applied magnetic field, samples with different spacer thicknesses (9, and 98 μm, respectively) have different curvature elasticity therefore show different dynamic behaviors. Moreover, because of the Freedericks transition, the real part of permittivity (at lower frequency ranges) increases with increasing applied magnetic field. Additionally, magneto-relaxation times of two samples are determined and the results reveal that due to the molecular anisotropic, the different directions of optical indexes exhibit different transmittance characteristics. Also, the results of dielectric analysis are found to agree well with the optical measurements.