Structural Study of Modified Bi4V2O10+deltaPhases (delta=0, 0.5, 1): Influence of Antimony Contribution

Three solid solutions of general composition Bi4-xSbxV2O10, Bi4V4+2-yV5+yO10+y/2, and Bi4V2-zSbzO11have been investigated in the fivefold Bi2O3–V2O5–V2O4–Sb2O3–Sb2O5system. These oxides have been characterized by X-ray diffraction and electron microscopy techniques. Single phases have been isolated for values ranging from 0 tox,z=0.8 andy=2. Single crystals of Bi3.2Sb0.8V2O10, Bi4V2O10.5, and Bi4V1.2Sb0.8O11have been grown and their structures determined by X-ray diffraction methods. The three oxides crystallize in the orthorhombic system, space groups F222, Amam, and Fmmm, respectively. Their structures keep the classical two-dimensional array of Aurivillius-like oxides with (Bi, Sb)–O layers interleaved with (V, Sb) –O sheets. It has been found that Sb3+is introduced into the bismuth layer, due to its similar sterical behavior, by the presence of a 5s2lone pair associated with Sb3+and 6s2associated with Bi3+, whereas Sb5+substitutes for the V5+cation. All of the substitutions carried out mainly act on the vanadium layer, which can accommodate different coordination polyhedra for cations: tetrahedra for V5+, square pyramids and distorted trigonal bipyramids or octahedra for V4+and V5+, and octahedra for Sb5+. This fact can be related to the electrical properties, such as high ionic conduction and ferroelectricity, shown by these types of materials.