Abstract:
Polycrystalline Fe2.5Zn0.5-xMnxO4 with x= 0.00-0.50 have been synthesized by the standard
solid state reaction technique. Pellet- and toroid -shaped samples are prepared from the ferrite
powders and sintered at various temperatures in air for 5 hours (1100-1250C). Structural and
surface morphology are studied by X-ray diffraction (XRD) and Field Emission Scanning
Electron Microscope (FESEM). The magnetic properties of these ferrites are characterized
with high frequency (10 kHz-120 MHz) using Impedance Analyzer. The influence of
microstructure, various cation distribution and sintering temperature on the complex initial
permeability of these samples are discussed. XRD pattern show the formation of spinel
structure. Lattice parameters are calculated using the Nelson -Riley function. Lattice
parameters are also analyzed by the Rietveld quantitative analysis. It is also found that the
lattice constant increases with increasing Mn content, obeying Vegard’s law due to larger
ionic radius (0.89Å) of Mn2+ compared to Zn2+ (0.74Å ). The micrograph shows that both
sintering temperatures and cations substitutions have great influence on various properties.
As the sintering temperature increases, the bulk density increases (depending on
compositions), and hence the porosity decreases for all compositions. The initial permeability
increases for substitution up to x=0.40 and beyond this slightly decrease. It is also observed
that the real part of initial permeability ( /
i ) increases with sintering temperatures because
high sintering temperature helps to develop uniform grain. The /
i remains fairly constant in
the frequency range up to some critical frequency which is called resonance frequency. The
highest /
i has been observed sintered at 1250 ºC because of the homogenious microstructure
with a uniform grain size distribution. The relative quality factor, Q, increases with increasing
sintering temperature and Mn content up to x=0.40 then decreases for increasing the Mn
content. The highest Q value (1013) is observed for Fe2.5Zn0.10Mn0.40O4 sintered at 1250ºC.