Anomalous electrical transport properties of polyvinyl alcohol-multiwall carbon nanotubes composites below room temperature

Abstract

The dc and ac electrical transport property of polyvinyl alcohol-multiwall carbon nanotubes composites has been investigated within a temperature range 77Յ T Յ 300 K and in the frequency range 20 Hz-1 MHz in presence as well as in absence of a transverse magnetic field up to 1 T. The dc conductivity follows variable range hopping model. The magnetoconductivity of the samples changes a sign from positive to negative with an increase in temperature which can be interpreted by the dominancy of the quantum interference effect over the wave function shrinkage effect. The ac conductivity follows a power law whereas the temperature dependence of frequency exponent s can be explained by correlated barrier hopping model. The dielectric behavior of the samples has been governed by the grain and grain boundary resistance and capacitance. The ac conductivity reduces with the application of magnetic field. Although the theoretical model to explain it, is still lacking, we may conclude that this is due to the increase in grain and grain boundary resistance by the application of magnetic field.

Structural characterization and observation of variable range hopping conduction mechanism at high temperature in CdSe quantum dot solids

“…These variation of e 0 and tan d with temperature may be due to interfacial polarization which again arises due to structural inhomogeneity and large degree of dispersion within the interfacial diffusion layer present between the electrode. 43 With large thermal energy, degree of freedom of the dipoles increases, accordingly e 0 and tan d increases because applied electric field now can align a large number of dipoles. 26 Now considering an ideal equivalent circuit consisting of resistances and capacitances, [44][45][46][47][48] originating from grain and interfacial grain boundary, respectively, then we can express complex impedance of the system as…”

Dielectric properties of novel PVA/ZnO hybrid nanocomposite films

“…As a result, a sudden decrease in e 0 and increase in conductivity at lower frequency region. This anomalous behavior in PVA composites attracted research due to its anomalous behavior in conduction mechanism [16,17].…”

EMI shielding and conductivity of carbon nanotube-polymer composites at terahertz frequency

“…The frequency exponent s is defined as s dlnσ∕dlnω [13]. This model has successfully been applied for a large class of composite materials in the frequency range starting from near d.c. value to THz frequency range [13][14][15][16][17][18]. In general, the conductivity remains almost constant ∼σ0 up to a characteristic onset frequency ω 0 , defined as σω 0 1.1σ0 [14], and then it increases following a power law Aω s .…”