Dielectric and electro-optical properties of ferric oxide nanoparticles doped 4-octyloxy-4’ cyanobiphenyl liquid crystal-based nanocomposites for advanced display systems

ABSTRACT

Doping of ferric oxide (Fe₂O₃) nanoparticles in 4-octyloxy-4ʹ cyanobiphenyl (8OCB) liquid crystal compound embedded in sample cells formed by photolithographic technique. The dielectric spectroscopy is investigated over a wide frequency from 500 Hz to 10 MHz. Various parameters such as switching time (τ_on and τ_off), dielectric permittivity (ε’), dielectric loss (ε”), relaxation frequency and optical texture of pristine 8OCB and 8OCB-Fe₂O₃ nanocomposite were investigated as functions of frequency and temperature. Moreover, splay elastic constant (k₁₁), rotational viscosity (γ) as a function of weight % of Fe₂O₃ NPs have also been investigated. These values are strongly affected by the presence of Fe₂O₃ NPs due to the enhancement of molecular ordering. The doped Fe₂O₃ NPs within the 8OCB LC may align along the director ñ strongly favours a splay distortion of ñ as the orientational order is increased. Optical image showed an improved molecular ordering of 8OCB with doping of Fe₂O₃ NPs. The dielectric anisotropy (Δε) of 8OCB-Fe₂O₃ nanocomposites was found to be reduced whereas threshold voltage (V_th) increased with increasing the doping of Fe₂O₃ NPs within the 8OCB. In addition to this, Fe₂O₃ NPs alter the magnitude of the perpendicular and parallel component of dielectric permittivity of nanocomposite.

KEYWORDS:

• Dielectric permittivity
• dielectric relaxation spectra
• nanoparticles
• response time
• threshold voltage
• doping
• splay elastic constant
• rotational viscosity

Acknowledgements

Authors are thankful to Prof. Shri Singh, Department of Physics, Banaras Hindu University, for his valuable support during drafting the manuscript and experiments.

Disclosure statement

No potential conflict of interest was reported by the author.