Influence of Ca2+ ions substitution on structural, microstructural, electrical and magnetic properties of Mg0.2−xCaxMn0.5Zn0.3Fe2O4 ferrites

Mg–Ca–Mn–Zn ferrites having general formula Mg0.2−xCaxMn0.3Zn0.5Fe2O4 (x = 0, 0.10, 0.15 and 0.20) were synthesized using solid state reaction method and sintered at 1100 and 1200 °C for 4 h. Structural, microstructural and elemental analyses of synthesized ferrites were performed by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and energy dispersive analysis of X-ray. A cubical spinel crystal structure with secondary phases is conformed in synthesized samples by XRD analysis. The lattice parameter decreased initially and then increases at x = 0.20 at 1100 °C. On contrary, the lattice parameter increases with Ca2+ ions concentration at 1200 °C which is attributed due to the different ionic radius of Mg2+ and Ca2+ ions. The FTIR spectra show the presence of high frequency and low frequency band at 559.36–460.14 cm−1 at 1100 °C and 549.71–558.35 cm−1 at 1200 °C corresponding to the tetrahedral and the octahedral sites. The SEM images revealed that the average grain size increases with the increase of Ca2+ ions concentration which may be attributed due to the fact that Ca2+ ions influences the microstructure by forming a liquid phase during sintering process and expedites the grain growth by lowering the rate of cation interdiffusion. Low frequency dielectric dispersion is consistent with the Maxwell–Wagner interfacial polarization. Dielectric constant increases with Ca2+ concentration for both sintering temperatures. The samples x = 0.10 and 0.15 exhibits highest conductivity at 1100 and 1200 °C, respectively because the electron hopping between Fe3+ and Fe2+ ions increases. The conduction process is attributed due to the presence of grain and grain boundary effect as revealed by the impedance study. The significant decrement in permeability with Ca2+ concentration is attributed due to the lower saturation magnetization and increased inner stress or crystal magnetic anisotropy.