Structural, Electrical and Dielectric Properties of Co-Mn Spinel Nanoferrites Prepared by Co-precipitation Technique

Cobalt manganese nanoceramics with nominal composition Co(1-x) Mn (x) Fe(2)O(4) (x=0.00, 0.15, 0.30, 0.45, 0.60, 0.75) were synthesized by a chemical coprecipitation technique. The X-ray diffraction patterns revealed the cubic spinel structure. The average crystallite size from the Sherrer formula was in the range of 28 nm-56 nm. The lattice parameter increased with a concentration of manganese. Scanning electron microscopy (SEM) was used for microstructural study. The electrical properties such as electrical resistivity (rho), drift mobility (mu (d)), and activation energy (Delta E) were measured using a two-probe apparatus in the temperature range 323-573 K. The electrical resistivity decreased with temperature and manganese concentration. The dielectric constant (epsilon'), loss factor or imaginary loss (epsilon aEuro(3)) and dielectric tangent loss (tan delta) were measured at room temperature using a LCR meter in the frequency range 100 Hz to 5 MHz. All the dielectric parameters decreased with increasing frequency. The AC electrical conductivity (sigma (ac)) was calculated from the dielectric measurements. It increases with increase of frequency and manganese concentration. The increase in electrical conductivity may be attributed to the formation of Co(+3) and Mn(+3) from Co(+2) and Mn(+3), respectively, at both A and B sites.