Journal of Materials Science, Vol.46, No.16, 5447-5453, 2011
Processing issues related to the bi-dimensional ionic conductivity of BIMEVOX ceramics
Bismuth vanadate, Bi(4)V(2)O(11), and its doped variations, Bi(4)(Co(0.15)V(0.85))(2)O(11), Bi(4)(Cu(0.1)V(0.9))(2)O(11), and Bi(4)(Cu(0.05)Ti(0.05)V(0.90))(2)O(11) 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 Bi(4)(Cu(0.05)Ti(0.05)V(0.90))(2)O(11) 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 x 10 (-2) (Omega cm) (-1)) at 500 A degrees 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 Bi(4)(Cu(0.05)Ti(0.05)V(0.90))(2)O(11) are prepared for the first time, with only moderate texturing achieved. We assert that the lack of texture in Bi(4)(Cu(0.05)Ti(0.05)V(0.90))(2)O(11) is responsible for the higher conductivity measured through the sample thickness when compared to Bi(4)(Co(0.15)V(0.85))(2)O(11), Bi(4)(Cu(0.1)V(0.9))(2)O(11) and other related compounds.