Low temperature synthesis and effect of Co doping on structural, optical and dielectric properties of CuCrO2 hexagonal nanoplates

Abstract In this research work, delafossite oxide CuCrO2 and its different Co doped compositions CuCr1-xCoxO2 (x = 0.05, 0.1, 0.15) were successfully synthesized by low temperature hydrothermal method. X-ray diffraction (XRD) confirmed the formation of CuCrO2 nanostructures with hexagonal structure having crystallite size less than 100 nm. The XRD peaks also confirmed that the fraction of Cr ions are perfectly replaced by the Co ions in the lattice structure. The crystallite size was found to decrease with increasing the doping concentration. The formation of nanoplates with hexagonal morphology was studied by using scanning electron microscope (SEM). The Fourier transform infrared spectroscopy (FTIR) was employed to analyze the occurrence of various functional groups, stretching and vibrational modes. Tauc's relation was used to calculate the optical band gap (Eg) of the samples from the absorbance spectra. Eg was observed to increase from 3.61eV to 3.95 eV which may be attributed to the reduction in crystallite size as a result of Co doping. The doping concentration also increases the density of grain boundaries which in turn induced the lattice strain in the crystal structure. The interplanar spacing d was observed to increase from 2.489 A to 2.508 A resulted due to induced strain. A maximum strain of 0.0132 was found in CuCr0.85Co0.15O2. The impedance and dielectric dispersion of the material were measured using LCR meter. The Cole-Cole plots represent the perfect dielectric behaviour of these materials indicating the pre dominant grain boundary resistance. The dielectric constant showed the increasing behaviour with Co doping concentration. Our results show that manipulation of the band gap and dielectric properties of CuCrO2 nanoplates with doping of Co ions can broadly enhance the efficiency and the applications of these oxide materials.