Study of nanostructural and non-adiabatic small polaron hopping conduction in nanostructured Bi2O3 - Fe2O3 – BaTiO3

Abstract

The nanostructured samples of BFBT were synthesized by mixing a stoichiometric ratio of the reactants (Bi2O3 - Fe2O3 – BaTiO3) in a high-energy planetary ball mill system. The mixture was mechanically milled for 1, 2, 5, and 10 h. Structural characterization of the mechanosynthesized powder for 5h followed by heat-treatment at 673, 873, and 1073K for 5 h has been investigated through the X-ray diffraction technique. After 5 h of mechanical milling and heat-treatment at 873K for 5 h, HRTEM confirmed the nanostructure of BFBT two samples with an average particle size of 14.79 and 49.77 nm, respectively. The effect of the heat-treatment temperature of nanostructured BFBT samples on their conductivity is studied in conformity with Mott’s theory. The measurements of electrical conductivity and thermoelectric power show the semiconductor behavior of the prepared samples. The increase in crystal size of the heat-treated nanostructured BFBT samples decreases the grain boundaries, leading to the conductivity enhancement. The conduction was predominantly caused by electronic transport between Fe ions, which revealed the non-adiabatic SPH. The hopping carrier mobility was found to be the primary factor for determining the conductivity in the nanostructured BFBT system. The Greaves model for variable range hopping (VRH) was investigated for the prepared samples.