The doubly-doped bismuth vanadate with Al and Ti having formula unit, Bi 2 V 1-x Al x/2 Ti x/2 O 5.5-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

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... radual stabilization of the tetragonal phase of Bi 2 VO 5.5-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 (R g ) and grain boundary resistances (R gb ) 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. vanadate, Bi 2 VO 5.5-δ (where δ denotes the oxygen-ion vacancy) surfaced in the late eighties is of immense importance because of its visibly good ionic conductivity values at relatively low temperature viz. 0.2 S·cm -1 at ~600 ℃ [6]. However, the problem with this compound is of multiple phase transitions (i.e., α↔β and β↔γ between 420 and 450 ℃ and between 540 and 560 ℃ , respectively) and the highest conductivity is found in tetragonal polymorph known as γ-polymorph or phase [6, 7] . Therefore, stabilization of this phase at room temperature is essential. The 490