Dielectric studies of dispersions of carbon nanotubes in liquid crystal 5CB

• Опубліковано в: : Semiconductor Physics Quantum Electronics & Optoelectronics
• Дата: 2008
• Автори: Koval'chuk, A., Dolgov, L., Yaroshchuk, O.
• Формат: Стаття
• Мова: Англійська
• Опубліковано: Інститут фізики напівпровідників імені В.Є. Лашкарьова НАН України 2008
• Онлайн доступ: https://nasplib.isofts.kiev.ua/handle/123456789/119076
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Цитувати: Dielectric studies of dispersions of carbon nanotubes in liquid crystal 5CB / A. Koval'chuk, L. Dolgov, O. Yaroshchuk // Semiconductor Physics Quantum Electronics & Optoelectronics. — 2008. — Т. 11, № 4. — С. 337-341. — Бібліогр.: 21 назв. — англ.

The frequency dependences of the imaginary ε″ and real ε′ parts of complex
 dielectric permittivity inherent to planarly aligned layers of nematic liquid crystals 5CB
 doped with multiwalled carbon nanotubes (CNT) were investigated in a wide range of
 frequencies (f = 10⁻²-10⁶
 Hz) and CNT concentrations (c = 0-0.25 wt.%). It has been
 shown that the studied frequency range can be divided in three parts according to
 behavior of ε′ (f) and ε″ (f) curves. The low-frequency range (10⁻² < f < 10¹ Hz) reflects
 the near-electrode processes in the cell. The ratio ε″/ε′ used to characterize these
 processes sharply grows if the concentration of CNT exceeds 0.05 wt.%. The moderate
 frequency range (10¹ < f < 10⁵
 Hz) corresponds to the alternating current conductivity,
 σАС. At the nanotubes concentration less than 0.025 wt.%, σАС does not depend on the
 frequency that implies its ionic origin. In its turn, at the c ≥ 0.025 wt.%, σАС is a power
 function of the frequency that is typical for electronic hopping mechanism. The transition
 from the ionic to electronic conductivity can be explained by the percolation theory with
 the critical concentration of nanotubes 0.031 wt.% and percolation parameter 2.5. The
 high-frequency range (10⁵ < f < 10⁶
 ) is mainly attributed to dipole volume polarization.
 For c < 0.05 wt.% such polarization is well described by the Debye equation. The time of
 dielectric relaxation in this frequency range increases with nanotubes content. This is
 explained by effective interaction of nanotubes with 5CB molecules.