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 degrees 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 degrees C. On contrary, the lattice parameter increases with Ca2+ ions concentration at 1200 degrees 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 degrees C and 549.71-558.35 cm(-1) at 1200 degrees 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 degrees 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.