Structural, Optical and Dielectric Properties of Solvothermally Synthesized NiCo 2 O 4 Nanoparticles for Optoelectronic Applications

The solvothermal method was used to form Nickel Cobalt Oxide (NiCo 2 O 4 ) nanoparticles, which were then thoroughly characterized to assess the suitability for optoelectronic applications. A pure cubic inverse spinel phase with a mean crystallite size of 16 nm determined by Scherrer analysis was confirmed by X-ray diffraction (XRD). Phase purity was confirmed by Raman spectroscopy using distinctive Co–O and Ni–O vibrational modes at 495 cm −1 and 681 cm −1 , which correspond to the spinel structure’s F 2 g and A1g symmetry modes. Selected area electron diffraction (SAED) ring patterns produced an average particle size of 18.76 nm, which was in close agreement with the XRD result and high-resolution transmission electron microscopy (HRTEM) showed well-resolved lattice fringes confirming the high crystallinity of the nanoparticles. UV–Vis spectroscopy revealed strong visible-region absorption with a direct optical band gap of 2.03 eV, suggesting improved photon harvesting capability. Dielectric spectroscopy confirmed the material’s significant polarizability by showing frequency-dependent permittivity consistent with Maxwell-Wagner interfacial polarization, with the dielectric constant rising with temperature and falling with increasing frequency. NiCo 2 O 4 nanoparticles are a promising option for semiconductor and optoelectronic device applications due to their visible-range band gap, high polarizability, and nanoscale crystallinity.