Investigation of dielectric and optical properties of structurally modified bismuth ferrite nanomaterials.

We present the effects of size and oxygen defects on electrical and optical properties of nano crystalline bismuth ferrite (BiFeO 3 ) with rhombohedral symmetry synthesized by solution evaporation method. The effects of oxygen vacancies on the behavior of system have been studied by annealing all samples under two different environments, air and oxygen. Single phase crystal structure was confirmed by X-Ray diffraction (XRD). The crystalline size calculated by Scherrer's formula falls in the range of 11–21 nm for air and 20–29 nm in case of oxygen annealing atmosphere. The crystalline size was confirmed by Transmission electron microscope (TEM). Dielectric response reveals that both dielectric constant and dissipation factor (tanδ) decrease with increase of frequency without depicting any peak. Optical studies showed that the system possesses an indirect energy gap whose value increases with increasing particle size. There is an evidence for the presence of intra band states in this system arising from defect states. [ABSTRACT FROM AUTHOR]