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.
