Structural and initial permeability studies of Y substituted Mn0.5Zn0.5Fe2-xYxO4 ferrites

Abstract

Polycrystalline Mn0.5Zn0.5Fe2-xYxO4 ferrites with x= 0.00, 0.05, 0.10, 0.15 0.20, 0.25 and 0.30 were synthesized by the standard solid state reaction technique. Pellet- and toroid -shaped samples were prepared from the ferrite powders and sintered at various temperatures in air for 5 hours. Structural and surface morphology of the ferrites were studied by X-ray diffraction (XRD) method and Scanning Electron Microscopy (SEM), respectively. The magnetic properties of these ferrites were characterized by a high frequency (100 KHz-120 MHz) Impedance Analyzer. The influence of microstructure, various cation distribution and sintering temperature on the complex initial permeability of these samples are discussed. XRD patterns show the formation of spinel crystal structure. Lattice parameters are calculated using the Nelson -Riley function. There is an enhancement of the unit cell dimension depending on Y substitutions in these compositions. This result is explained with the help of ionic radii of substituted cations. The SEM micrographs show that both sintering temperatures and cations substitutions have great influence on the average grain size. As the sintering temperature increases, the bulk density of the samples increases (depending on compositions), and hence the porosity decreases for all compositions. The initial permeability value increases with increasing average grain size of the samples. It is also observed that the real part of initial permeability is found to increase with sintering temperatures for all ferrites because high sintering temperature helps to develop uniform grain. The real part of the initial permeability remains fairly constant in the frequency range up to a critical frequency which is called resonance frequency. The natural resonance frequency of Mn0.5Zn0.5Fe1.9Y0.1O4 is observed to be 2.82 MHz. The relative quality factor is found to be the maximum (3477) for the sample sintered at 1400oC.