Experimental and First-Principles Investigations of Lattice Strain Effect on Electronic and Optical Properties of Biotemplated BiFeO3 Nanoparticles

High purity BiFeO3 nanoparticles were successfully prepared by employing a green and facile biotemplated method which utilized polysaccharides of κ-carrageenan. The particles’ size of BiFeO3 nanoparticles exhibited significant correlations between structural, electronic, and optical properties that have been investigated by both experimental and first-principles methods. First-principles calculations were performed by means of density functional theory (DFT). Structural analysis revealed that the all-prepared BiFeO3 was crystallized in a rhombohedrally distorted structure, along with an average crystallite size of 14.59 nm. The refined lattice parameter and crystal volume obtained by means of the Rietveld refinement method indicated a good agreement with the calculated data; the lattice strain is found in BiFeO3 nanoparticles. From the linear fit using the Kulbeka–Munk method, a small direct and indirect optical energy gap was found to be 2.17 and 1.84 eV, respectively. In addition, first-principles studies in relation to lattice strain effect on electronic properties of BiFeO3 have thus far revealed that the calculated energy band gap decreases with the increase and decrease of lattice parameters. Our results which were obtained by means of the facile green route and first-principles approaches could shed new insights on the lattice strain effect on physical properties of BiFeO3 nanoparticles.