Ca–Li substitution driven structural, dynamics of electron density, magnetic and optical properties of BiFeO3 nanoparticles

Abstract Ca and Ca–Li substitution dependent modification in structural, electron density, vibrational, magnetic and optical properties of BiFeO3 nanoparticles synthesized by tartaric acid based sol–gel route are reported. X-ray diffraction and transmission electron microscopy techniques revealed the phase purity and nanocrystalline nature of BiFeO3, Bi0·95Ca0·05FeO3, Bi0·95Ca0·05Fe0·95Li0·05O3 samples. The electron density plots indicated the displacement of Bi and Fe ions and partial covalency of Bi–O and Fe–O the bonds. The Ca and Ca–Li ions substitution induced distortion in rhombohedral structure resulting in enhanced magnetization of BiFeO3 nanoparticles. The magnetization is highest for Ca–Li substituted BiFeO3 nanoparticles with saturation magnetization of 0.036 emu/g due to the canted spin structure and uncompensated surface spins. The enhanced magnetic properties are also endorsed by the electron spin resonance and Raman studies. The band-gap of BiFeO3 nanoparticles can be tuned by aliovalent ions substitution from 2.26 eV for BiFeO3 to 2.20 and 2.17 eV for Ca, and Ca–Li substituted BiFeO3 nanoparticles respectively.