Controlled fabrication and characterization of microspherical FeCO3 and α-Fe2O3.

In this paper, the microspherical Fe(2)O(3) was successfully obtained by calcining the FeCO(3) sphere prepared by a hydrothermal route. The sphere morphology perfectly remained after the calcination of FeCO(3) but the diameter of sphere decreased in a certain degree from 70-100 μm to 50-70 μm, which might be due to some loss of quantity during the calcination (FeCO(3)-Fe(2)O(3)). The sphere was solid and highly densified. At the same time, the effects of factors influencing the formation of FeCO(3), such as PVP, reaction temperature were investigated. The simple formation process of FeCO(3) was also proposed as follows: Fe(2+) produced by the reduction of Fe(3+) reacted with CO(3)(2-) released from the decomposition of urea to form FeCO(3) nanoparticle. Then, the formed nanoparticles aggregated together to produce sphere structure via oriented attachment. With the reaction time increasing, the sphere became solidness and densification.