Adiabatic small polaron hopping conduction in nanostructured Bi2O3–Fe2O3–PbTiO3 prepared by high energy planetary ball mill

Abstract

Nanostructured 0.52 Bi2O3–0.18 Fe2O3–0.30 PbTiO3 (BFPT) mol% sample was prepared via a high-energy planetary ball mill. To obtain nanostructured materials, the mixture was mechanically milled for 1, 2, 5, and 25 h. The heat treating process was applied to the milled BFPT sample at 673, 873, and 1073 K for 5 h. The amorphous natures of the as-milled and crystallized formed phases of the heat treated samples are examined using the X-ray diffraction (XRD) technique. HRTEM and XRD were used to confirm the amorphous nature and nanocrystallization of the milled and the heat treated BFPT samples, respectively. The effect of the heat-treatment temperature of BFPT samples on their dc electrical conductivity (σ), density (ρ), and oxygen molar volume (Vm) was studied. The results of the thermoelectric power indicate a p-type semiconducting behavior of the BFPT samples. The high temperature (above θD/2) dependent on conductivity was explicated by the small polaron hopping (SPH) model. While Greaves’ variable range hopping (VRH) model was studied at intermediate temperatures. The physical parameters determined from the best fits of these models were thought to be reasonable and consistent with the BFPT samples. The hopping carrier mobility was found to be the dominant factor for determining the conductivity in the BFPT samples. The electronic transport between Fe ions was primarily responsible for the conduction, which was shown to obey the adiabatic SPH.