Impact of strontium titanate nanoparticles on the dielectric, electro-optical and electrical response of a nematic liquid crystal

Abstract

The impact of ferroelectric nanoparticles (FNPs), namely strontium titanate (SrTiO3) on the dielectric, electro-optical and electrical response of a room temperature nematic liquid crystal (NLC), 5CB (4-pentyl-4′-cyanobiphenyl) is investigated through dielectric, electro-optical and electrical techniques. The dielectric studies clearly show that low frequency dielectric relaxation shifts towards higher frequency as concentration of FNPs increases but decreases to the value even lower than pure sample at 2 wt% concentration. Afterwards, the short axis molecular relaxation observed in homeotropic cell obtained from homogeneous aligned cell by applying bias voltage higher than threshold shifts towards higher frequency by ∼ 28 % in composites but remains independent of concentration. Interestingly, after the removal of bias voltage, dielectric spectra does not return to its original state even after ∼ 22 min in the composites unlike pure sample and could be considered as apparent dielectric memory (i.e. memory effect). However, the voltage dependent optical textures confirm the short term memory in the composites. The electrical response recorded as a function of frequency in the composite is also significantly different than pure sample which further confirms the impact of FNPs on NLC. We believe that the observed effects of FNPs on dielectric, electro-optical and electrical behavior could be due to the plausible favorable interaction among FNPs and NLC molecules. Such investigations would certainly be pivotal in tuning the dielectric and electro-optical properties of NLCs using FNPs and helpful in designing the next-generation tunable electro-optical and soft memory based devices.