Investigation of temperature-dependent conduction mechanism in MnCo_2O_4/polypyrrole nanocomposites by three-dimensional variable range hopping (3D-VRH)and band-conduction model

摘要

Nanoparticles of manganese cobalt oxide (MnCo_2O_4) have been prepared with the hydrothermal method, while nanocomposites of MnCo_2O_4/polypyrrole (MCO/PPy) have been prepared by dispersing MCO nanoparticles in the PPy matrix by an in situ chemical polymerization method. MCO/PPy nanocomposites' structural characterizations were made by x-ray diffraction (XRD) and field-emission scanning electron microscope (FESEM). XRD and FESEM analyses give evidence that MCO nanoparticles are dispersed uniformly, and there is an effect on crystallinity and particle size. The observed shift in the stretching vibrations of Fourier transform infrared spectra for MCO/PPy nanocomposites confirms the interaction between MCO nanoparticles and PPy. Furthermore, the temperature-dependent (300-453 K) DC conductivity measurements of MCO/PPy nanocomposites depict the presence of different conduction mechanisms. The conductivity data are well fitted by the 3D variable range hopping (3D-VRH) model and the band conduction model at low and high temperatures. The characteristic temperature (T_0) calculated from the 3D-VRH and the activation energy (E_a) calculated from the band conduction model support the observed highest conductivity for the 10 wt. % MCO/PPy nanocomposite.