Enhancing the structural, optical, magnetic and ferroelectric properties of perovskite BiFeO3 through metal substitution

Abstract

Nanocrystalline BiFeO3 materials with multiferroic properties were successfully prepared using the solution-combustion method, and the impact of Ni-substitution in bismuth ferrite was investigated in the present research. Structural phase identification was done through XRD and FTIR spectroscopy. The average crystallite size was determined to be 44.87 nm for the pristine sample and 32.52 nm for the Ni-substituted ferrite. An enhancement in lattice strain, leading to crystal defects, was observed with Ni substitution in bismuth ferrite. Elemental analysis by EDX revealed the presence of Ni, Fe, Bi, and O in the substituted ferrites. FESEM studies indicated a significant decrease in the size of agglomerated and porous grains from 137 nm to 102 nm with the substitution of Ni in pristine bismuth ferrite. A considerable increase in the band gap from 2.21 eV to 2.39 eV was observed with Ni-substitution in the prepared ferrite phase, possibly due to the decrease in crystallite size. The very low coercivity (1.509 Oe) of pristine bismuth ferrite indicates its superparamagnetic behaviour. An improvement in saturation magnetization (almost two times) and a slight increase in coercivity (2.042 Oe) were found with Ni-substitution at Fe3+ sites in bismuth ferrite compared to the pristine ferrite. At 10 KHz, Ni-substitution enhanced the dielectric constant and decreased the dielectric loss of the prepared bismuth ferrite materials. Ferroelectric investigation of the prepared ferrites indicated an improvement in the P-E loop of Ni-substituted bismuth ferrite with a reduced loop area, indicating low electrical leakage.