Influence of A-site off-stoichiomety on grain conductivity and oxygen relaxation behavior of Na0.5Bi0.5TiO3 ceramics

Abstract The electrical performances and relaxation behaviors of the Na 0.525 Bi 0.475 TiO 2.975 and Bi-deficient Na 0.51 Bi 0.48 TiO 2.975 sample were investigated. The grain conductivity of the Na 0.525 Bi 0.475 TiO 2.975 sample is able to reach 1.51 × 10 −3  S/cm at 673 K. In the temperature range of measurement, the grain conductivity of the Bi-deficient Na 0.51 Bi 0.48 TiO 2.975 sample is lower than that of the Na 0.525 Bi 0.475 TiO 2.975 sample. By the internal friction and dielectric relaxation spectrum, the activation energy and relaxation time at infinite temperature were determined as (0.82 eV, 2.47 × 10 −14  s), (0.67 eV, 5.82 × 10 −12  s) and (0.85 eV, 5.8 × 10 −13  s), (0.52 eV, 2.55 × 10 −10  s) for the Na 0.525 Bi 0.475 TiO 2.975 and Na 0.51 Bi 0.48 TiO 2.975 samples at the different temperature regions. In the Na 0.525 Bi 0.475 TiO 2.975 compound, there is larger specific free volume, higher mobile oxygen vacancy content and better oxygen vacancy mobility, which cause the higher grain conductivity in the Na 0.525 Bi 0.475 TiO 2.975 compound. To some extent, by the Bi-deficient method, oxygen vacancies can be introduced into the Na 0.51 Bi 0.48 TiO 2.975 compound and the grain conductivity may be improved, but the other side of Bi-deficiency harms the oxygen vacancy diffusion capacities in the Na 0.5 Bi 0.5 TiO 3 compound.