Experimental and theoretical elucidation of dielectric behavior of MgO-r-GO nanocomposites

Dielectric behavior of MgO and r-GO containing (MgO-r-GO) nanocomposite is elucidated in the frequency range 1 kHz-1 MHz at fixed temperatures in the range 300-473 K. Three MgO-r-GO nanocomposite samples are synthesized by molecular-level mixing technique by varying the r-GO content and are named as MgO-0.05G, MgO-0.1G and MgO-0.15G in the increasing order of r-GO content. At 1 kHz and 300 K, dielectric permittivity (epsilon') values of MgO-0.05, MgO-0.1G and MgO-0.15G are measured as 10, 12 and 18, respectively, which enhanced to 358, 563 and 612, respectively at 473 K. All the composites exhibited non-Debye relaxation which could be explained using Havriliak-Negami (HN) relaxation function. The enhanced epsilon' values are found to vary as a function of both orientation and interfacial (Maxwell-Wagner) polarizations (due to the presence of oxygenated polar functional groups and defects). From the excellent fitting of the dielectric dispersion curves with HN relaxation function, it is inferred that at lower frequencies (and at 473 K), the interfacial polarization is much stronger in comparison with the same at room temperature, which is attributed to the impeded motions of migrating charges (surface or free charge carriers) and their trapping within the large number of interfaces in the composites.