Processing issues related to the bi-dimensional ionic conductivity of BIMEVOX ceramics

Bismuth vanadate, Bi₄V₂O₁₁, and its doped variations, Bi₄(Co_0.15V_0.85)₂O₁₁, Bi₄(Cu_0.1V_0.9)₂O₁₁, and Bi₄(Cu_0.05Ti_0.05V_0.90)₂O₁₁ are investigated with respect to relative processability and total conductivity. In conventionally prepared (pressure-less sintered) ceramic disks, the single-substitution compounds show signs of exaggerated grain growth with significant c-axis preferred orientation. The doubly substituted Bi₄(Cu_0.05Ti_0.05V_0.90)₂O₁₁ is found to have the widest processing window, resulting in sintered monoliths with the highest relative density and no preferred orientation. It also shows the highest conductivity (7 × 10⁻² (Ωcm)⁻¹) at 500 °C, as measured by impedance spectroscopy. Activation energies for conduction of the four compounds are reported and found to be comparable to earlier study. Hot forged samples of Bi₄(Cu_0.05Ti_0.05V_0.90)₂O₁₁ are prepared for the first time, with only moderate texturing achieved. We assert that the lack of texture in Bi₄(Cu_0.05Ti_0.05V_0.90)₂O₁₁ is responsible for the higher conductivity measured through the sample thickness when compared to Bi₄(Co_0.15V_0.85)₂O₁₁, Bi₄(Cu_0.1V_0.9)₂O₁₁ and other related compounds.