Effect of calcination temperature on optical, magnetic and dielectric properties of Sol-Gel synthesized Ni0.2Mg0.8-xZnxFe2O4 (x = 0.0–0.8)

Abstract The Ni0.2Mg0.8-xZnxFe2O4 (x = 0.0, 0.2, 0.4, 0.6 & 0.8) nanomaterials were prepared via sol-gel technique. These samples were calcined at three different temperatures (T) such as 400, 450 and 500 °C/5 h. Furthermore, the X-ray diffraction (XRD) patterns of all the calcined samples revealed the single phase cubic spinel structure. The lattice constants (a = b = c) were noticed to be increasing with increase of ‘x’. The grain shape, size and distribution of x = 0.0–0.8 contents were analyzed using field emission electron microscope (FESEM). The x = 0.2 content provided higher optical band gap energy (Eg) value than the remaining contents. Furthermore, the magnetization versus magnetic field (M − H) curves indicated the superparamagnetic nature of x = 0.0–0.8 contents. The high saturation magnetization (Ms) was noticed for x = 0.4 and 0.6 contents. In addition, the distribution of cations like Ni+2, Mg+2, Zn+2, Fe+3 and Fe+2 was performed between the tetrahedral (A) and octahedral (B) sites. The frequency dependence of dielectric constant (e′), dielectric loss (e") and ac-electrical conductivity (σac) was investigated as a function of composition. Moreover, the temperature variation of e′ showed the decreasing trend of dielectric transition temperature (Te) with increase of ‘x’. The high e′ of 163.1 (at 1 MHz) was noticed at x = 0.2 content calcined at 500 °C. Using the power law fit applied to the log σac-log ω plots, the dc-electrical conductivity (σdc) and exponent (n) parameters were calculated.