Abstract

• The main aim of the research is to study structural, electrical and optical properties of LiNi1-xCoxO2 (0.3 ≤ x ≤ 0.5) nanocrystalline powder. LiNi1-xCoxO2 (0.3 ≤ x ≤ 0.5) nanocrystalline powders were prepared by a modified sol–gel method using lithium nitrate (LiNO3), cobalt(II) nitrate (Co(NO3)2.6H2O) and nickel(II) nitrate (Ni(NO3)2.6H2O) as starting materials, de-ionized water as solvent, citric acid (C6H8O7.H2O) as chelating agents and carboxy methyl cellulose as dispersant agent. The prepared samples were calcined at 800 °C. The calcined powder was made as pellet form by using cold pressing method. The pellets were sintered at 900 °C. The pellets of LiNi1-xCoxO2 were characterized by XRD, FT IR and SEM. Electrical properties were examined by LCR meter in the frequency range 100 kHz – 2 MHz and frequency depended on prepared sample. The optical properties were investigated by UV-Vis spectrophotometer. From XRD data, the observed values of the average crystallite sizes of LiNi0.7Co0.3O2, LiNi0.6Co0.4O2 and LiNi0.5Co0.5O2 sintered at 900 °C were 13.58 nm, 44.31 nm and 48.03 nm, respectively. By increasing Co doping level, the average crystallite size also increased. FT IR spectra indicated the presence of the stretching vibrations of metal-oxygen (Ni-O and Co-O) chemical bonds. The spherical-shaped nanocrystalline powders were observed in SEM images. Electrical measurement revealed that the ac conductivity increased with increase in frequency. The ac conductivity of LiNi0.5Co0.5O2 was lower than those of other two prepared nanopowder samples (LiNi0.7Co0.3O2 and LiNi0.6Co0.4O2). The value of ac conductivity was between 10-2 and 10-4 S cm-1 . Dielectric constants and dielectric loss were found to decrease with increase in frequency. The experimental results indicated that the ac conductivity, dielectric constant and dielectric loss of prepared samples depend on the frequencies. From UVVis data, the optical band gap values of LiNi0.7Co0.3O2, LiNi0.6Co0.4O2 and LiNi0.5Co0.5O2 nanopowder samples were found to be 3.2, 3.4 and 3.6 eV, respectively. These band gap values (Eg) are also reliable within semiconductor band gap range.