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

摘要

Cobalt manganese nanoceramics with nominal composition Co_(1-x)Mn_xFe_2O_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 microstruc-tural study. The electrical properties such as electrical resistivity (ρ), drift mobility (μ_d), and activation energy (△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 (ε'), loss factor or imaginary loss {ε") and dielectric tangent loss (tan 8) 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 (σ_(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.