Exploring the role of transition metal ions doping on the optical, magnetic and energy storage properties of Bi0.96Eu0.04FeO3 nanoparticles

Abstract

Bismuth ferrite has been quite extensively studied because of its unique multiferroic properties. The introduction of dopants strategically at the ‘A’ and ‘B’ sites has been known to improve the multiferroic properties of bismuth ferrite. This study focuses on the detailed investigation of the structural, morphological, optical, magnetic, and electrochemical properties of sol-gel synthesized bismuth ferrite as well as Bi0.96Eu0.04Fe0.95M0.05O3(M=Mn, Cu, Co, Zn) nanoparticles. The crystal structure and morphological analysis are done using XRD, Rietveld refinement, and FESEM. The XRD analysis and Rietveld Refinement have confirmed a structural transition to the orthorhombic phase upon simultaneous co-doping of ‘Eu’ and ‘M’(M= Mn, Cu, Co, Zn) ions at the ‘A’ and ‘B’ sites respectively. The evidence of different ratios of mixed valence states of ‘Fe’ and oxygen vacancies in the co-doped nanoparticles dictates the enhanced magnetic properties. There is a significant decrease in the band-gap of co-doped nanoparticles obtained from Tauc’s plot, with the lowest achieved band-gap of 1.8 eV in the case of ‘Eu’ and ‘Mn’ doped nanoparticles. Room-temperature M-H loops have recorded an increase in the value of maximum magnetization from 0.1 emu/g in case of pristine bismuth ferrite to 0.79 emu/g for ‘Eu’ and ‘Co’ doped bismuth ferrite nanoparticles. The unsaturated loops, however, have confirmed the presence of anti-ferromagnetic component along with the ferromagnetic part. The electrochemical studies have shown superior specific capacitance in co-doped bismuth ferrite, with the maximum specific capacitance of 273 F/g for ‘Eu’ and ‘Zn’ doped bismuth ferrite. It has also shown remarkable capacitive retention of 84.8 % after 5000 cycles at 10 A/g.