Synthesis of cobalt-doped bismuth vanadate by combustion-synthesis: Influence of fuel on phase content and morphology

Cobalt (15 at.%) doped bismuth vanadate, Bi₄(V_0.85Co_0.15)₂O_11-δ (BICOVOX0.15), is known to have high oxygen ion conduction in the medium temperature range (400–600 °C). Small grain size may be important in stabilizing the highly conductive and disordered γ-phase at lower temperature. In this article, we report for the first time the synthesis of highly porous nanoscale BICOVOX powders by a solution combustion technique. The effects of fuel-to-oxidizer ratio, and postcombustion heat treatment temperature and time on the phase content and microstructure of the powders were investigated. As-combusted powders were revealed to be a mixture of Bi₂O₃, BiVO₄, and γ-BICOVOX phases that were converted to phase pure γ-BICOVOX during heat treatment.