Frequency and temperature dependent dielectric behavior of NiCr2O4 spinels synthesized via sol-gel route – Effect of sintering temperature

Nickel chromite spinel, represented by the chemical formula NiCr2O4, were synthesized through the sol–gel (auto-combustion) method. The samples were subsequently subjected to sintering at temperatures of 700, 900, 1100, and 1300°C. The XRD data analyzed at room temperature employed the Rietveld refinement method to ascertain the material's phase. The dielectric constant, loss tangent, and AC conductivity were measured using an LCR meter at room temperature and across a temperature range of 100 to 800°C, at frequencies ranging from 100 Hz to 10 MHz. The plots of the dielectric constant ϵ′ against frequency indicate that the dielectric characteristics of NiCr2O4 spinel are representative of expected behavior. The dielectric loss variance (ϵ″) for each sample exhibits a decreasing trend with respect to frequency. The Nyquist plot demonstrates the occurrence of phenomena like grain and grain boundaries at specific temperatures. The evidence of Maxwell–Wagner interfacial polarization significantly strengthened the findings. With increasing frequency and temperature in the range of 100°C to 800°C, a significant reduction in the dielectric properties is observed.