Microstructural interpretation of vibrational properties and ionic transport mechanism in Dy stabilized δ-Bi2O3

Abstract

The correlation of structure and microstructure with vibrational property and ionic conduction mechanism of Bi1-xDyxO1.5-δ (0.10 ≤ x ≤ 0.40) for different doping concentration has been investigated. Room temperature δ-phase stabilization of cubic Bi2O3 has been achieved by adding Dy2O3 as the dopant, using a low temperature citrate-auto-ignition method. The Rietveld refinement of the X-ray diffraction profiles has given detailed microstructural information of the prepared samples, which corroborates with TEM study. The Raman spectroscopy study clearly indicated the structural evolution due to Dy doping. Effect of doping concentration on vibrational property of δ-Bi2O3 has been investigated in detail. Impedance spectroscopy studies of the samples exhibited thermally activated non-Debye type relaxation process. A structural model has been used to explain the ion transport mechanism in the samples. The bulk conductivity, measured from impedance spectra and frequency independent part of ac conductivity of each of these compounds show Arrhenius type behavior. The random free-energy barrier model has been utilized to analyze the frequency dependence of the conductivity. Both impedance spectroscopy and ac conductivity analysis exhibited that the composition Bi0.75Dy0.25O1.5-δ shows maximum value of conductivity. Comparable values of activation energies, obtained from different parameters, indicated that the ions follow the same type of mechanism for conduction as well as for relaxation.