Comparative Analysis of Dielectric Properties of ZnO and NiO Nanoparticles for Energy Storage Application

Nickel oxide (NiO) and zinc oxide (ZnO) nanoparticles were synthesized via an eco-friendly solution-combustion method utilizing lemon juice as a biofuel. Structural, morphological, and dielectric properties were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and dielectric spectroscopy. Rietveld refinement of XRD data confirmed the nanocrystalline nature of both materials, with NiO exhibiting a face-centered cubic structure and ZnO adopting a hexagonal wurtzite configuration. SEM images revealed agglomerated particles with irregular morphology. Dielectric studies conducted over a frequency range of 50 Hz–1 MHz and temperatures of 30– 250 °C demonstrated that NiO possesses a significantly higher dielectric constant (12,000 at 50 Hz, 30 °C) compared to ZnO (480 at 50 Hz, 250 °C). While NiO showed superior energy storage potential, its higher dielectric loss indicates greater energy dissipation. Impedance and AC conductivity analyses highlighted temperature- and frequency-dependent behaviors, underscoring the suitability of these materials for energy-efficient devices.