Production and characterization of graphene based nano electroceramics

This thesis study involves the synthesis of nano electroceramics by the doping of graphene oxide at various ratios synthesized by the Hummers method into the Iron and Manganese compounds of Bismuth, Lanthanum and Yttrium prepared by the hydrothermal method.The obtained doped and undoped samples were characterized by XRD, SEM and EDX, TEM, FTIR, DTA-TGA, UV-VIS-NIR spectroscopy, ferroelectric measurements, temperature dependent electrical resistance changes and dielectric measurements. From the XRD results, it is observed that the obtained samples were in nanoscale and the crystal dimensions are changed with the doping of graphene oxide. SEM images and EDX spectra indicate that the nano electroceramics are formed from the large particles combined of small-sized particles. From the TEM images and SAD patterns of the samples, it is seen that the ceramic samples are consisted of nano-sized, all-directional grains with no oriented relationship between them in all directions. From FTIR spectra of the obtained samples, the chemical compositions of the samples were determined. FTIR spectra indicate that the graphene oxide changes the peak intensities. This confirms the incorporation of the graphene oxide into the ceramic structure. With the help of thermal analysis measurements, the reactions occurring in the structure of the samples at increasing temperature, reaction temperatures, reaction energies and total mass losses were determined. The optical band gaps of the samples were determined by optical absorption method. The doping of the graphene oxide changes the optical band gaps of the samples. Dielectric parameters and alternating current conductivity of the produced nano electroceramics were measured depending on the frequency. The dielectric constants of the samples are changed with the doping ratios. The DC electrical conductivity measurements confirm the semiconducting behavior of the samples. The maximum polarization, residual polarization and coercive electric field values of the nanoelectro-ceramics were determined with the help of polarization-electric field hysteresis loops. The ferroelectric behavior of the samples were changed by the doping of graphene oxide. The obtained results indicate that the electronic and nanostructure of the synthesized electroceramics can be controlled by the doping of graphene oxide for electronic and energy applications.