Dielectric Relaxation Processes in Mn2O3/Reduced Graphene Oxide Nanocomposites

One essential for developing electronic materials for device applications is an understanding of the materials' dynamic relaxation processes. This paper seeks to improve our understanding of the relaxation processes in pure Mn2O3 and Mn2O3/reduced graphene oxide (RGO) nanocomposites on the basis of the capacitive contributions of grain and grain boundaries (GBs). To achieve this, the dielectric properties for pure Mn2O3 and Mn2O3/xRGO (x = 5, 10 and 20 wt.%) nanocomposites, prepared theby sol-gel method, were investigated over a wide frequency range at room temperature using a broadband dielectric spectrometer (BDS). Crystalline structure, molecular structure and microstructure of samples were characterized by x-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscope, respectively. XRD analysis showed the formation of orthorhombic crystalline structure in all samples with no considerable changes in the crystalline structure. FTIR spectra did not show new absorption bands upon introducing the graphene content. Characteristic peaks corresponding to Mn-O vibration were found to have shifted to lower wavenumbers, indicating an increase of particle size. The dielectric study showed some changes in the dielectric properties of the Mn2O3/RGO nanocomposites. For pure Mn2O3, two relaxation processes were clearly observed; the slower one positioned at high relaxation time (tau = 1.7 x 10(-2) s) is associated to the GBs capacitive contribution, while the faster one of lower tau (= 2.5 x 10(-5) s) is associated to the grain capacitive contribution. For Mn2O3/RGO nanocomposites, tau for both process slightly increased with increasing RGO up to 10 wt.% then remarkably decreased to much lower values at 20 wt.%. Interestingly, BDS, rather than XRD and FTIR techniques, is considered as a powerful and sensitive technique, even for small changes in Mn2O3/RGO nanocomposites.