Effect of Bi2O3 addition on structure and magnetic properties of Ni0.5Zn0.5Fe2O4 nanofibers

Ni 0.5 Zn 0.5 Fe 2 O 4 nanofibers with addition of 0–5 wt% Bi 2 O 3 were synthesized by calcination of the electrospun polyvinylpyrrolidone/inorganic composite nanofibers at the temperature below the melting point of Bi 2 O 3 . The effects of Bi 2 O 3 addition on the phase structure, morphology and magnetic properties of the nanofibers were investigated by means of X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, selected area electron diffraction and vibrating sample magnetometer. It is found that the nanofiber diameter, crystallite size and magnetic parameters can be effectively tuned by simply adjusting the amount of Bi 2 O 3 addition. The average diameter of Ni 0.5 Zn 0.5 Fe 2 O 4 nanofibers doped with different contents of Bi 2 O 3 ranges from 40 to 63 nm and gradually decreases with increasing Bi 2 O 3 content. The addition of Bi 2 O 3 does not induce the phase change and all the samples are a single-phase spinel structure. The amorphous Bi 2 O 3 tends to concentrate on the nanoparticle surface and/or grain boundary and can retard the particles motion as well as the grain growth, resulting in a considerable reduction in grain size compared to the pristine sample. The specific saturation magnetization and coercivity of the nanofibers gradually decrease with the increase of Bi 2 O 3 amount. Such behaviors are explained on the basis of chemical composition, surface effect, domain structure and crystal anisotropy.