Cobalt-doped Bi26Mo10O69: Crystal structure and conductivity

A series of cobalt-doped bismuth molybdates were synthesized and investigated using X-ray powder diffraction, transmission electron microscopy and impedance spectroscopy. The ranges of solid solution were determined. Two new compounds, Bi1−xCox[Bi12O14]Mo5O34.5±δ (x=0.2) and Bi[Bi12O14]Mo5−yCoyO34.5±δ (y=0.2), which crystallise in monoclinic unit cells have been examined in detail by diffraction methods. Impedance spectroscopy measurements show that the studied materials are good ionic conductors with conductivity values about 5×10−3S×cm−1 at 973K and 1.7×10−4S×cm−1 at 623K, which are similar to conductivity values of yttrium substituted zirconia and (YSZ) gadolinium doped ceria (CGO). Measured and calculated diffraction spectra for Bi12.8Co0.2Mo5O34±δ and projection of the Bi12.8Co0.2Mo5O34±δ crystal structure onto the ac plane. [Display omitted] •The limit of the Bi1−xCox[Bi12O14]Mo5O34.5±δ homogeneity range is equal to x=0.2.•The limit of the Bi[Bi12O14]Mo5−yCoyO34.5±δ homogeneity range is equal to y=0.2.•Solid solutions have monoclinic symmetry. No phase transition is observed.•The conductivity at 700° for y=0.2 solid solutions is equal to −lg σ, S×cm−1=2.23.•The conductivity at 350° for y=0.2 solid solutions is equal to −lg σ, S×cm−1=3.74.