Synthesis and properties of barium ferrite nano-powders by chemical co-precipitation method

Nano-powders with controllable particle size, excellent magnetic properties and thermal stability of barium hexaferrite (BaFe12O19) have been synthesized via a co-precipitation/calcination technique. The phase composition, morphology and magnetic/thermal properties of the products were systematically studied. XRD patterns reveal that a long co-precipitation reaction time (5 h) and high calcination temperature (1100 °C) are beneficial for the formation of BaFe12O19 phase and decreasing the tendency to agglomeration. SEM micrographs show that the products show a hexagonal flake-like particle shape and the size are well controlled and maintained at single-domain particle size range area (<460 nm), above which the coercivity will decrease abruptly for the coupling exchange among particles. The products with jHc of 5934 Oe, temperature coefficient of remanence (αBr) of −0.176% K−1 and temperature coefficient of coercivity (βjHc) of 0.0427% K−1 were obtained when co-precipitated for 5 h and calcined at 900 °C for 2 h. A high saturation magnetization of 66.9 emu/g was obtained when co-precipitated for 5 h and calcined at 1100 °C for 2 h, approaching the theoretical saturation magnetization (72 emu/g).