Tuning refractive indices in nematic liquid crystal via nanoparticles coupling

Liquid Crystals (LCs), with their exclusive ability to combine fluidity and optical anisotropy, continue to play a pivotal role in designing and developing future generations of novel and efficient photonic and electro-optic materials. In this paper, a comprehensive investigation is made into the influence of ferroelectric nanoparticle addition on nematic liquid crystals’ optical and structural properties, particularly concentrating on modifying refractive indices and orientational ordering. For that purpose, ferroelectric nanoparticles of bismuth ferrite (BiFeO₃) and barium titanate (BaTiO₃) have been mixed with nematic LC material E7. The temperature dependence of ordinary and extraordinary refractive indices was experimentally measured and quantitatively analyzed with a profound understanding of theoretical concepts of refractive indices and optical anisotropy. The findings of our research clearly indicate that addition of nanoparticles not only increases optical anisotropy but also increases heat stability of nematic substances. It is found that doping E7 with BaTiO₃ significantly promotes refractive indices and orientational ordering in a concentration of 0.2 to 0.4%wt, but addition of ferroelectric nanoparticles of BiFeO₃ improves heat stability of LC molecules significantly; this can be ascribed to the ferroelectric and magnetic interactions produced on LC–nanoparticles interfaces.