Thermal, optical and dielectric properties of phase stabilized δ - Dy-Bi2O3 ionic conductors

In this work, we have investigated the thermal, structural, optical and dielectric properties of Bi0.75Dy0.25O1.5-delta (0.10 <= x <= 0.40) ionic conductors prepared by citrate auto-ignition method. The Thermo gravimetric-DTA analysis and X-Ray Diffraction pattern confirm the single delta-phase stabilization of doped system beyond 25 mol% doping concentration. XRD analysis also indicates that average crystallite size is maximum and micro strain is minimum for Bi0.75Dy0.25O1.5-delta composition. The optical band gap of the prepared compositions is obtained from the Ultraviolet-Visible spectroscopy that shows a red shift with the increase in Dy content. The presence of different structural bonds is confirmed from FT-IR spectroscopy analysis. Ionic transport property of the prepared compositions has been analyzed using Nyquist plot for dc conduction and Nernst-Einstein relation for ac conduction mechanism. This analysis indicates that the composition Bi0.75Dy0.25O1.5-delta shows highest conductivity. The dielectric properties of these ionic conductors have been analyzed using Havriliak Negami (BN) formalism. The dielectric permittivity epsilon'(omega) of all the prepared compositions is found to be within the range 1.61-3.63(x10(2)) in S.I. unit. Analysis of electric modulus data reveals that dielectric and modulus relaxation follows same mechanism. The time-temperature superposition principle has been verified from the scaling of modulus spectra.