Physical, structural, morphological, magnetic and electrical properties of Co0.5-xNixZn0.5Fe2O4 nanocrystalline ferrites

A series of Co0.5-xNixZn0.5Fe2O4 (x = 0-0.25 insteps of 0.05) nano crystalline ferrites were synthesized in combustion method using citric acid as fuel. Densities and porosities were calculated using the lattice constant and Archimedes's principle. A linear increase in experimental density and a decrease in porosity were observed with increase in nickel concentration. Cationic distribution was proposed on the basis of theoretical lattice constant and it was correlated with the variation in magnetic and electrical properties of all samples. TEM image of the sample with nickel concentration x = 0.15 indicated the existence of nano-metric range particles and the sample was characterized with the help of inter-planar spacing(s) from SAED pattern. Morphological and surface analysis was studies using Scanning Electron Microscopy and well developed nearly spherical grains were observed with increase in nickel concentration. Energy Dispersive Spectroscopic (EDS) analysis was performed for all nickel substituted samples and all displayed stoichiometric proportions of ions in the samples as per the chemical composition. Elemental mapping was done for all samples using EDS data. Curie temperature was dropped nearly 90 degrees C at the end of the series. Initial permeability showed slight variation with an increase in nickel concentration and it remained nearly constant with frequency up to 3 MHz. Magnetic loss was observed to be constant for all samples after 100 kHz. DC Electrical resistivities of all samples were measured and all samples displayed resistivity in the order of 10(8) Omega-cm. AC resistivity and dielectric studies were conducted from 100 Hz to 5 MHz for all samples. Dielectric constant and losses of all samples exhibited very low values compared to that of conventional ferrites. The electrical properties of all samples were discussed with the help of temperature variation of resistivity, activation energy, grain size, density and porosity.