Co-precipitated magnetoplumbite nanoparticles and their structural and dielectric properties

Chromium doped strontium hexaferrites with the general formula SrFe_12-xCr_xO₁₉ having chromium contribution; x= 0.0, 0.1, 0.2, 0.3 were prepared by co-precipitation method. All the samples were calcined at 910°C for 20 minutes and then sintered at 920°C for 20 minutes. Structural analysis was done on these samples by X-Ray diffraction (XRD). Using XRD data crystal structure, phase purity and crystallite size were determined. The final structure of the materials under study was hexagonal. The observed crystallite sizes by using Scherrer formula were in the range from 40 to 52 nm. Morphological analysis was done by scanning electron microscopy (SEM) and by this the nature of the nanomaterials under study was found out to be particle i.e. nanoparticles. The dielectric constant, dielectric loss tangent and AC electrical conductivity of the samples were determined as a function of frequency at different temperatures from 100°C to 700°C, with the step of 200°C. DC electrical resistivity was also done as a function of temperature. The investigation results of the AC electrical properties showed that with increase in temperature the magnitude of dielectric constant is increasing but is decreasing with increase in frequency. The trend of the dielectric loss was observed to be increasing with the increase in temperature. The AC electrical conductivity increases with the increase in temperature due to the phenomenon of enhanced hopping. The DC electrical resistivity graphs proved that with the increase in temperature the resistivity decreases and conductivity increases. All the electrical properties showed a strong correlation with structural properties. With the addition of chromium, resistivity of the materials increased, indicating lower energy losses due to eddy currents. Reduced eddy current losses make the chromium doped strontium hexaferrites, a potential candidate for efficient devices operated at- high frequencies.