Correlation of defect structure and ionic conductivity in δ-phase solid solutions in the Bi3NbO7-Bi3YO6 system

Defect structure and conductivity behaviour are discussed in the solid solution Bi3Nb1−xYxO7−x(0.0 ≤ x ≤ 1.0). Investigations were carried out using a combination of ac impedance spectroscopy and powder X-ray and neutron diffraction. Low temperature conductivity and activation energy both increase as a function of x. The former is attributed to an increase in oxide ion vacancy concentration, whereas the latter is due a redistribution of oxide ion vacancies as determined by neutron diffraction measurements. The defect structures at room temperature and 800 °C are presented. Curvature in Arrhenius plots of conductivity throughout the composition range is associated with a temperature dependent redistribution of oxide ions.