Anomalous dielectric behavior and correlation of barrier hopping mechanism with ferroelectricity in solvent assisted phase pure bismuth iron oxide nanoparticles

Abstract

Phase pure bismuth iron oxide (BiFeO3) nanoparticles (NPs) are synthesized using sol-gel route; acetic acid (AA) and ethylene glycol (EG) are used as solvents. Nanoparticles synthesized using AA as solvent result in amorphous behavior under as-synthesized condition. Phase pure BiFeO3 is obtained after calcination at 200 °C. Whereas, mixed BiFeO3 and Bi2Fe4O9 phases are observed after calcination at 300 °C. Nanoparticles synthesized using EG as solvent result in phase pure BiFeO3 even under as-synthesized conditions. Strengthening of phase pure BiFeO3 is observed after calcination at 300 °C. TEM result shows spherical morphology of nanoparticles with average size ˜12 nm after calcination at 300 °C using EG as solvent. Higher value of dielectric constant (i.e. ˜1050) and low tangent loss (i.e. ˜0.001), at log f = 7.3, are observed for EG based nanoparticles. Variation in conductivity with change in temperature is studied in detail using Jonscher’s power law. AC electrical conduction is associated with correlated barrier-hopping mechanism. Bismuth iron oxide nanoparticles exhibit room temperature ferroelectricity for both of the solvents used i.e. acetic acid and ethylene glycol. Low electrical coercivity and maximum polarization (Pmax˜12.22 μC/cm2) are observed for EG based nanoparticles. Correlation of barrier hopping mechanism and ferroelectricity has been observed in these nanoparticles especially prepared with EG as solvent because of the phase purity.