Electrical and magnetic properties of BiFeO3 nanoparticles substituted with high concentrations of cobalt

The 10% and 20% Co-substituted BiFeO3 (BFO) samples were prepared by co-precipitation method. The microstructure, phases formed, electrical and magnetic properties were investigated. The cobalt-substituted BiFe1−xO3 (where x = 0.0, 0.1, and 0.2) showed formation of BiFeO3 (BFO), Bi25FeO40, CoFeO4, and Bi2Fe4O9 phases. The lattice parameter value “a” decreased and “c” increased for BFO as a result of Co substitution, thereby increasing lattice cell volume. The surface morphology and grain shape and size were studied by scanning electron microscope. Enhanced dielectric properties are studied for the Co-substituted BFO nanoparticles. At low frequency, BFO showed dielectric constant value of 40 which increased to 52 and 402 for 10% and 20% Co-substituted BFO samples, respectively. The electrical conductivity in the temperature range 300–700 °C showed semiconducting behavior. Remanence (Mr), saturation magnetization (Ms), and coercivity (Hc) values for BFO are 0.123 emu/g, 6.178 emu/g, and 108.59 G, respectively. The Ms, Mr, and Hc values for 10% cobalt and 20% Co-substituted BFO are 5.742 emu/g, 0.213 emu/g, and 124.86 G and 42.777 emu/g, 24.255 emu/g, and 4127.55 G, respectively. It is concluded that synthesis of pure BiFeO3 is not possible and increase in magnetic parameters are due to the formation of cobalt ferrite.