Analysis of size-dependent variation in nonlinear absorption coefficient of multiferroic bismuth ferrite nanoparticles synthesized at different sintering temperature

Third-order nonlinear optical property of multiferroic bismuth ferrite (BiFeO3) nanoparticles sintered at different temperatures has been studied by employing Z-Scan technique. BiFeO3 (BFO) nanoparticles (NPs) were synthesized by the sol-gel process with different sintering temperature of 823 K, 923 K and 1023 K. XRD reveals that all samples have single-phase rhombohedral structure with R3c space group with no secondary phases present. The calculated crystallite size for samples sintered at 823 K, 923 K and 1023 K is found to be 75 nm, 87 nm and 94 nm, respectively. Crystal structure parameters and phase analysis of the BFO samples are obtained by the Rietveld refinement (FullProf) method. FTIR spectra show the absorbance peaks at 448 cm(-1) and 533 cm(-1) which confirm the synthesis of NPs. SEM images show the agglomerated spherical particles. Average crystallite and particle size of the samples are found to increase by increasing the sintering temperature. EDX verifies the constituent elements and reveals that stoichiometry in sample preparation is well-matched with the atomic ratio of the experimental quantity. The nonlinear absorption coefficient is characterized by the Z-Scan method employing continuous wave (CW) laser operating at 532nm wavelength. Nonlinear absorption coefficient (beta), evaluated by open aperture Z-scan data, is found to decrease with an increase in the particle size of the BFO NPs. BFO nanoparticles synthesized by optimizing the synthesis temperature can be used for the various applications of futuristic multiferroic and optical devices.