Variable range hopping conduction in yttrium–graphene oxide nanocomposites

The raw material, graphite powder, was processed by means of the modified Hummers’ method to yield graphene oxide (GO). The rare-earth yttrium (Y) ion was added to it in controlled concentrations to get Y–GO nanocomposites. The morphology of the samples was studied using transmission electron microscopy (TEM) and scanning electron microscopy (SEM) analyses. Analysis of the TEM and SEM images revealed agglomerated nanoclusters of yttrium along with rolled sheets of graphene and wrinkled surface morphology for the samples. The structural analysis was done using X-ray diffraction studies (XRD) and compared with the standard data. The electron diffraction rings were indexed using selected area electron diffraction (SAED) with the help of CrysTBox software. The weight and atomic percentages of individual chemical constituents in the composites were analyzed using energy-dispersive X-ray (EDX) spectroscopy. The confocal Raman spectra of the samples provide helpful information on their optical band transitions. The UV–Vis reflectance spectral analysis supports the findings of the Raman studies. Additionally, DC electrical conductivity studies of the samples in the low-temperature region indicate their semiconducting nature, and the Arrhenius plots were used to determine their activation enthalpies. A comparative study of Mott variable range hopping (VRH) and its modified version, Efros–Shklovskii VRH, was applied in the low-temperature region to study the charge carrier transport properties of the samples. Graphical abstract