Structural Studies of the Fast Oxygen Ion Conductor BICOVOX.15 by Single-Crystal Neutron Diffraction at Room Temperature

✍ Scribed by C. Muller; M. Anne; M. Bacmann; M. Bonnet

• Publisher: Elsevier Science
• Year: 1998
• Tongue: English
• Weight: 442 KB
• Volume: 141
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1998.7974

✦ Synopsis

The room temperature crystal structure of the fast oxygen ion conductor Bi 4 (V 0.85 Co 0.15 ) 2 O 11؊ (BICOVOX.15) was refined within the average tetragonal unit cell from single-crystal neutron diffraction data. The unit cell dimensions are a T ‫؍‬ 3.929(2) A s and c T ‫)9(674.51؍‬ A s in space group I4/mmm with Z ‫؍‬ 1. The conventional R w factor is 0.067. The structure consists of intergrowth, along the c-axis, of alternating (Bi 2 O 2 ) 2؉ sheets and (VO 3.5 ᮀ 0.5 ) 2؊ oxygen-deficient perovskite-like layers. The compound, which exhibits a high ionic conductivity at moderate temperatures, undergoes a phase transition around 780 K between the disordered high-temperature -phase and the lower temperature -phase, showing a modulated superstructure. Oxygen vacancies are localized in the perovskite-like layers, oxygen stoichiometry is derived, and oxygen diffusion paths are proposed for the -phase at room temperature.