Influence of Na substitution on structural, magnetic, optical and photocatalytic properties of bismuth ferrite nanoparticles

We have reported the influence of Na substitution on structural, magnetic, optical and photocatalytic properties of sol–gel route synthesized Bi1−xNaxFeO3 (x = 0.0, 0.02, 0.04, 0.06 and 0.08) nanoparticles. Rietveld refinement of the XRD data and electron microscopy techniques revealed the phase purity and nanocrystalline nature of Bi1−xNaxFeO3 samples. The substitution of Na1+ leads to the structural distortion in BiFeO3 nanoparticles which is apparent from the XRD Rietveld refinement and Raman spectroscopy studies. The ferromagnetic ordering parameters increase with increasing Na content in BiFeO3 nanoparticles and the highest magnetization 0.91 emu/g at 30kOe is observed for x = 0.08 sample. The observed enhanced ferromagnetic behaviour of Bi1−xNaxFeO3 nanoparticles are also endorsed by the ESR analysis. The energy bandgap of BiFeO3 nanoparticles is altered by aliovalent Na ions substitution from 2.16 to 2.03 eV. Compared to pristine BiFeO3, the Na-substituted BiFeO3 nanoparticles revealed the much-advanced photocatalytic activity of methylene blue (MB) and crystal violet (CV) under UV–visible light irradiation. In the irradiation time of 100 min, Bi0.96Na0.04FeO3 nanoparticles showed ~ 95% MB and ~ 84% CV degradation. The outstanding changes in the magnetic and photocatalytic properties of Bi1−xNaxFeO3 nanoparticles are due to the differences in the ionic radii, aliovalency between the Bi3+ and Na1+ ions and oxygen vacancies.