Processing issues related to the bi-dimensional ionic conductivity of BIMEVOX ceramics
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Bismuth vanadate, Bi4V2O11, and its doped variations, Bi4(Co0.15V0.85)2O11, Bi4(Cu0.1V0.9)2O11, and Bi4(Cu0.05Ti0.05V0.90)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(Cu0.05Ti0.05V0.90)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(Cu0.05Ti0.05V0.90)2O11 are prepared for the first time, with only moderate texturing achieved. We assert that the lack of texture in Bi4(Cu0.05Ti0.05V0.90)2O11 is responsible for the higher conductivity measured through the sample thickness when compared to Bi4(Co0.15V0.85)2O11, Bi4(Cu0.1V0.9)2O11 and other related compounds.
KeywordsBiVO4 Molten Salt Synthesis Bismuth Vanadate Substitution Compound Relative Bulk Density
Funding from the Deutscher Akademischer Austauschdienst (DAAD) to support a summer research visit by the principal author to the University of Bayreuth is gratefully acknowledged.
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