Electric impedance investigation with inductive behavior of multiwalled carbon nanotubes doped with variable loadings of magnetite

Multiwalled carbon nanotubes (MWCNTs) loaded with different levels (1–50%) of magnetite (Fe₃O₄) m-MCNTs were prepared using the co-precipitation/hydrothermal method. The prepared samples were examined using Fourier-transform infrared spectroscopy (FTIR) and impedance spectroscopy techniques to characterize their structural and electrical properties. All measurements were conducted at room temperature. According to the FTIR analysis, the 20%-composite has high intensities of magnetite peaks indicating maximum amount of magnetite has been formed on the surface of the carbon nanotubes. The variation of the relative permittivity, the dielectric loss, the alternating current (AC) conductivity, and the electric modulus with frequency indicate that the dispersion is due to space charge polarization and electron hopping between Fe ions of different charge states. Nyquist plots showed an ellipse-like geometry, where the upper and lower parts pinpoint capacitive and inductive behaviors, respectively. The obtained results showed that the doped samples can be considered as materials with a resistive-inductive-capacitive behavior (RLC) with a resonance frequency of 4.7 MHz. Above this frequency, the dielectric constant becomes negative. The variation of the doping level between 1 and 50% has minimal effect on the various electric parameters.