Harvested and non-harvested tin thiohypodiphosphate (Sn₂P₂S₆) ferroelectric nanoparticles are used to dope the 4-n-octyl-4′-cyanobiphenyl liquid crystal (8CB). Due to their higher average spontaneous polarization, the harvested nanoparticles have stronger interactions with the liquid crystal molecules which leads to a higher order parameter as demonstrated by the increase in phase transition temperatures. This is confirmed by the results of dielectric characterization. In the homeotropic orientation, the increase in the order parameter leads to a higher dielectric permittivity. In the planar orientation, the coupling between the spontaneous polarization of the nanoparticles and the order parameter induces a slight reorientation of the liquid crystal director from the initial planar orientation, leading to an increase in the dielectric permittivity. This effect is more important for the liquid crystal doped with harvested nanoparticles.

In the present work, the dielectric properties of recycled liquid crystals (LCs) (non-purified, purified, and doped with diamond nanoparticles at 0.05, 0.1, and 0.2 wt%) were investigated. The studied LC mixtures were obtained from industrial recycling of end-of-life LC displays presenting mainly nematic phases. Dielectric measurements were carried out at room temperature on a frequency range from 0.1 to 10⁶ Hz using an impedance analyzer. The amplitude of the oscillating voltage was fixed at 1 V using cells with homogeneous and homeotropic alignments. Results show that the dielectric anisotropy of all purified samples presents positive values and decreases after the addition of diamond nanoparticles to the LC mixtures. DC conductivity values were obtained by applying the universal law of dielectric response proposed by Jonscher. In addition, conductivity of the doped LC mixtures is lower than that of the undoped and non-purified LC.

The influence of a low ac electric field on phase transitions is discussed in the case of a nematic liquid crystal $4-n-\text{octyl}-4{}^{\prime }$-cyanobiphenyl (8CB) doped with ${\text{Sn}}_2{\text{P}}_2{\text{S}}_6$ ferroelectric nanoparticles. The phase-transition temperatures obtained from temperature-dependent dielectric measurements were higher than those determined by the calorimetric method. This difference is explained by the presence of the measuring electric field which induces two effects. The first one is the amplification of the interactions between the nanoparticle polarization and the liquid-crystal order parameter. The second one is the field-induced disaggregation or aggregation process at high nanoparticle concentrations.