Size effect of submicron barium titanate particles on dielectric properties of smectic A liquid crystal 4-nitrophenyl 4'-decyloxy benzoate

The influence of barium titanate (BaTiO3) particles with sizes of 100, 200 and 400 nm on the dielectric properties of smectic A liquid crystal (LC) 4-nitrophenyl 4'-decyloxy benzoate (10 NF) was investigated by low-frequency dielectric spectroscopy. It is shown that BaTiO3 particles increase the longitudinal component of the dielectric permittivity of the LC more strongly than the transversal component. In other words, the anisotropy of dielectric permittivity is increased, which is crucial for improving the performance of electro-optic effect in LC. This is the result of the coupling of the polar axis of ferroelectric particles with the director at the moment of formation of the smectic A phase from the isotropic phase. The effect is maximal for particles with a size of 200 nm, which may be related to the monodomain structure of these particles. BaTiO3 particles also affect the dielectric dispersion of LCs, which can be explained on the basis of the local field concept.