Structure and oxide ion conductivity in tetragonal tungsten bronze BaBiNb5O15

Abstract

The crystal structure and electrical properties of a tetragonal tungsten bronze (TTB) compound, BaBiNb₅O₁₅, were investigated by high-resolution synchrotron X-ray powder diffraction and AC impedance spectroscopy. The compound is a new type of oxide ion conductor with a total electrical conductivity of 3 × 10⁻⁴ S cm⁻¹ at 600 °C and a relatively small activation energy (0.3–0.5 eV). It is suggested that the large amount of cationic vacancies in the A sites, the large free space created by the large Ba²⁺ cations, and the splits of the Bi atoms are in favor of oxygen ion migration. This stable tungsten bronze compound BaBiNb₅O₁₅ with moderate oxide ion conductivity shows potential for applications in SOFC anodes, amperometric gas sensors, and active catalyst supports.