Morphologies and magnetic properties of α-FeO nanoparticles calcined at different temperatures.

Different morphologies and sizes of α-FeO were prepared by a coprecipitation method using polyvinylpyrrolidone as a dispersant. In the preparation process, homogeneous and dispersed nanoscale FeOOH particles were first obtained by the coprecipitation method, and then the FeOOH particles were calcined at high temperature to form α-FeO. The growth and aggregation of the α-FeO particles at different calcination temperatures resulted in α-FeO powders with diversiform morphologies (nanoscale microsphere, pinecone ellipsoidal, polyhedral, and quasi-spherical structures).