Role of Al and Ti doping in modulating electrical properties of BIVOX system

Abstract

The doubly-doped bismuth vanadate with Al and Ti having formula unit, Bi2V1−xAlx/2Titx/2O5.5-δ (0.10 ⩽ x ⩽ 0.25) was synthesized. The specimens were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR), differential scanning calorimetric (DSC), UV-Vis, and electrochemical impedance spectroscopy (EIS) for their structural, thermal, optical, and electrical studies. Influence of both dopant cations (Al and Ti) was observed in the gradual stabilization of the tetragonal phase of Bi2VO5.5-δ with dopant amount. A non-uniform grain growth phenomenon was observed up to x = 0.175, with dopant addition. UV-Vis study revealed the comparatively higher order of oxide ion vacancies for the composition x = 0.175. Impedance spectroscopy measurements indicate a significant decrease of both the grain (Rg) and grain boundary resistances (Rgb) with the rise in temperature and the overall resistance is found to be dominated by the grain interior contribution. Enhancement of ionic conductivity was found in all the compositions in the intermediate temperature range as compared to the parent compound, and the single Al-doped system and the highest value were obtained for x = 0.175.