Inorganic Chemistry, Vol.52, No.9, 5206-5213, 2013
Interlayer Switching of Reduction in Layered Oxide, Bi4V2O11-delta (0 <= delta <= 1)
In contrast to the rich oxygen nonstoichiometry in vanadium oxides, we report here an interesting Bi4V2O11-delta oxide system whose vanadate layer allows only a narrow oxygen deficiency range. Beyond delta = 0.4, reduction of Bi4V2O11-delta does not proceed in the V-O layer, but instead suddenly switches to the Bi-O layer by precipitation of metallic bismuth. A new structure is realized for 0.4 <= delta <= 1, and its ordered V4+ cation forms a rigid V4+/V5+ = 2/3 pair giving rise to one-dimensional magnetism that can be understood in terms of an S = 1/2 antiferromagnetic Heisenberg chain model. In situ X-ray diffraction measurement yielded the first phase diagram for the system of current study and revealed the unusual phase relation as a function of oxygen nonstoichiometry. It is suggested that at higher temperatures than 570 degrees C all compositions would be unified into an oxygen disordered tetragonal phase, whose implication for oxide ion mobility could have significant impact on our understanding of ionic conduction.