Cobalt-doped Bi26Mo10O69: Crystal structure and conductivity

Abstract

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, Bi 1− x Co x [Bi 12 O 14 ]Mo 5 O 34.5± δ ( x =0.2) and Bi[Bi 12 O 14 ]Mo 5− y Co y O 34.5± 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 −3 S×cm −1 at 973 K and 1.7×10 −4 S×cm −1 at 623 K, which are similar to conductivity values of yttrium substituted zirconia and (YSZ) gadolinium doped ceria (CGO). Measured and calculated diffraction spectra for Bi 12.8 Co 0.2 Mo 5 O 34± δ and projection of the Bi 12.8 Co 0.2 Mo 5 O 34± δ crystal structure onto the ac plane. • The limit of the Bi 1− x Co x [Bi 12 O 14 ]Mo 5 O 34.5± δ homogeneity range is equal to x =0.2. • The limit of the Bi[Bi 12 O 14 ]Mo 5− y Co y O 34.5± 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 −l g σ , S×cm −1 =2.23. • The conductivity at 350° for y =0.2 solid solutions is equal to −l g σ , S×cm −1 =3.74.