Influence of the Annealing Temperature on the Structure and Properties of Bismuth Ferrites

This article presents samples of bismuth ferrite developed and synthesized by the authors using the solgel method. SEM images of such samples were obtained. The data from X-ray diffraction analysis and thermodynamic properties of these bismuth ferrites were studied. It was found that samples annealed at different temperatures have a granular microstructure with granule sizes from 20 to 100 nm. On a scale above 200 nm, all samples are morphologically indistinguishable. The X-ray diffraction study discovered the crystallinity of bismuth ferrites at a scale level of less than one nanometer. The sizes of nanocrystallites of bismuth ferrite and overall structural heterogeneity decrease with increasing annealing temperature. The thermodynamic analysis found a significant decrease in heat capacity, enthalpy, entropy and modulus of the Gibbs energy of the samples under study with an increase in the annealing temperature. This indicates an improvement in the structure due to reducing heat loss on structural defects. A direct correlation between the level of X-ray scattering on the studied samples and the thermodynamic properties of bismuth ferrites was established. There is reason to believe that by selecting an appropriate annealing temperature, it is possible to regulate the nanocrystallinity and thus other physical properties of bismuth ferrites.