Defect chemistry and electrical properties of sodium bismuth titanate perovskite

Abstract

We review the diversity of the electrical behaviour of NBT induced by various defect mechanisms, including A-site Na or Bi non-stoichiometry, isovalent-substitution, and acceptor- and donor-doping.

The effect of Fe‐acceptor doping on the electrical properties of Na1/2Bi1/2TiO3 and 0.94 (Na1/2Bi1/2)TiO3–0.06 BaTiO3

“…When the doping level reaches 2 mol% Fe, the total conductivity of all samples again increases by one additional order of magnitude until it saturates above a 2 mol% doping content. This finding again coincides well with recent findings on other acceptor dopants in NBT …”

“…However, at higher concentrations the oxygen vacancies are responsible for the dominant ionic conductivity. This behavior has already been reported as a typical feature of NBT based B‐site acceptor doped oxygen ionic conductors and was attributed to a phase and defect dipole formation dependent concentration of mobile vacancies . The total conductivity increases by at least four orders of magnitude over the whole temperature range and saturates for doping levels above 2 mol% Fe.…”

“…This is highly detrimental for piezoelectric applications and illustrates that knowledge of the defect chemical properties of lead‐based ferroelectrics cannot be directly transferred to the lead‐free successors. However, evidence has been provided that the complex formation in NBT is highly dependent on dopant concentration, or oxygen vacancy concentration, respectively . The higher the dopant concentration, the higher the concentration of mobile oxygen vacancies.…”

Cooperative mechanisms of oxygen vacancy stabilization and migration in the isolated tetrahedral anion Scheelite structure

“…The existence of a low level of oxide ion conduction in the parent BiVO 4 could be ascribed to the possible uncontrollable Bi deficiency owing to the volatilization of Bi 2 O 3 during the material preparation, which could result in the presence of oxygen vacancies. Bi nonstoichiometry effect on the oxide ion conduction has been demonstrated in Na 0.5 Bi 0.5 TiO 3 -based oxide ion conductors 38,39,41 .…”

“…The fluorite-like Bi-O sublattice, which is known as a highly polarizable bonding network 16,38,41 , could offer flexible environments to adapt for rotation and deformation of VO 4 tetrahedra, which is important for the stabilization and migration of oxygen vacancies in a tetrahedra-based structure. Therefore, the Bi-O lattice provides pathways with low diffusion barriers, which are highly beneficial for the migration of oxygen ions.…”