Dielectric properties and AC conductivity of nickel supported on silicon dioxide: facile synthesis and DFT calculation

Abstract

Composite based on silicon dioxide (SiO₂) with 5 wt% Ni (Ni/SiO₂) was synthesized via a facile incipient wet impregnation technique. The main purpose is to address the influence of Ni on the dielectric properties and AC conductivity of SiO₂. Impedance spectroscopy was employed in a frequency range of 1 kHz–300 kHz at various temperatures. The results revealed that the incorporation of Ni significantly enhanced the dielectric constant (ε′) and the AC conductivity (σ′) of SiO₂. The conductivity spectra σ′ (ν) showed Jonscher’s power law behavior, σ′ ~ ω^s. The temperature dependence of the exponent (s) suggests that the conduction mechanism is governed by the small polaron hopping mechanism. The bias voltage study on the dielectric performance of the samples was investigated at 100 kHz. The results revealed almost zero tunability, which could be attributed to the dominance of the bulk contribution to the permittivity. The I–V characteristic curves showed linear behavior with slope one demonstrating that the charge transport mechanism is ohmic in nature. Based on density functional theory DFT, a simple first-principle calculations were performed to examine the effect of Ni on the optical dielectric properties of SiO₂. In accordance with the experimental results, the calculations showed that the addition of Ni improved the optical dielectric constant of SiO₂. The improved dielectric performance, particularly at room temperature, suggests that the Ni/SiO₂ is a potential candidate for practical applications such as electric accessories and capacitors.