Nanocomposites and nanomaterials
Non-monotonous by the concentration of Cu6PS5Br nanoparticles conductivity of 6СВ nematic liquid crystal 
Luchynets M.M.1, Studenyak I.P.1, Poberezhetz S.I.2, Kovalchuk O.V.2
1 Uzhhorod National University, 46 Pidhirna Str., 88000, Uzhhorod, Ukraine
E-mail: luchynetsm@gmail.com
2Molecular Photoelectronics Department, Institute of Physics of the NAS of Ukraine, 46 Prospect Nauki, 03039, Kyiv, Ukraine

The influence of Cu6PS5Br superionic nanoparticles on dielectric properties of planar-oriented 6CB nematic liquid crystal was investigated in the frequency range of 5-106 Hz at a temperature of 293 K. The nanoparticles had a shape close to spherical, the average diameter was 200 nm. The concentration of nanoparticles in the liquid crystal varied within 0-0.1 wt.%.
Сomplex dielectric permittivity of 6CB liquid crystal with Cu6PS5Br superionic nanoparticles were obtained using the oscilloscopic method, considering that the equivalent pattern of the sample is the parallel connected resistance and capacitance. The value of the amplitude of the measuring signal voltage constituted 0.5 V, which was 4 times less than the voltage for the reorientation of the liquid crystal molecules.
It was shown that at frequencies below 100 Hz in the studied cells there is a relaxation process, which is described by the Debye relation. The nature of such a relaxation process and the influence of nanoparticles on its parameters are explained. It is shown that the liquid crystal conductivity is a nonmonotonic function on the concentration of nanoparticles. 
When introducing 0.01 wt.% of Cu6PS5Br superionic nanoparticles into the 6CB liquid crystal, conductivity is reduced by 1.5 times, and then, with concentration increase, it linearly increases reaching at 0.1 wt.% of Cu6PS5Br superionic nanoparticles the conductivity of liquid crystal without nanoparticles (5.10-7 S/m). Basing on the comparison of these results with those from the paper [1] the possible mechanisms of processes that lead to such dependence of the liquid crystal conductivity on the concentration of nanoparticles were described.

1. Tomylko S., Yaroshchuk O., Maschke U., Yamaguchi R. Dielectric properties of nematic liquid crystal modified with diamond nanoparticles // Ukr J Phys.-2012.-57.-P. 239-243.