Impact of SWCNT on structural, electrical, and dielectric properties of ZnO-SWCNT nanocomposites
摘要
The present work deals with the synthesis of zinc oxide (ZnO) by co-precipitation method. A series of nanocomposites with zinc oxide and single-walled carbon nanotubes (SWCNT) of varying concentrations were synthesized successfully. The nanocomposites were characterized by XRD, Raman spectroscopy, Scanning Electron Microscopy. The effect of SWCNT on the structural, electrical, and dielectric properties of the nanocomposites has been investigated. XRD analysis revealed that the crystallite size decreases, whereas the dislocation density and microstrain increase with the increase of SWCNT content. From the Raman spectra of the samples, pure zinc oxide shows broad peaks near 445, 580, 1150 cm−1, corresponding to E2H, E1(LO), and 2p stretching vibration modes of the zinc oxide compound. The G-band, around 1580 cm−1, which is prominently seen in the composite samples, is due to the tangential stretching mode of carbon atoms. The vibrational spectra also indicate the increase of defects or disorders (D band ~ 1350 cm−1) with the increase of SWCNT content. Room temperature frequency dependence of AC conductivity, dielectric constant, and dielectric loss of the composites has been investigated. DC conductivity values have been estimated from AC conductivity results and found that the maximum value obtained to be 2.22 × 10–5 S/m for 4% SWCNT of the composite sample. The dielectric response of the composites against the frequency variation fulfills the Maxwell–Wagner polarization model and Koop’s theory. The dielectric constant attains maximum of 10,000 at optimal concentrations of 4% SWCNT of the nanocomposite. The electrochemical analysis of cyclic voltammetry curves proved that the specific capacitance of ZC4 was obtained as 58 F/g. Incorporation of conductive SWCNT into ZnO matrix enhanced the AC conductivity, DC conductivity, and dielectric properties, indicating that the filler-matrix phases act like mini capacitors for conductive and dielectric properties, owing to increased interfacial area between the two phases. The electrochemical analysis of cyclic voltammetry curves proved that the specific capacitance of ZC4 was obtained as 58 F/g. The present features indicate that the conductive loss contribution gradually increases the total dielectric loss with the increase of SWCNT filler concentration. The current results proved that the newly developed zinc oxide and SWCNT nanocomposites are favorable materials for energy storage device applications.