Structural, defect, transport and dopant properties of AgNbO3

Silver niobate (AgNbO3) is a candidate lead-free piezoelectric materials with potential applications in electronic technology and catalysis. Atomistic simulation techniques are used to examine the defects, diffusion of Ag+ and O2‒ ions, solution of dopants and electronic structures of pristine and doped configurations in AgNbO3. The Ag Frenkel is the most favourable intrinsic defect leading to the formation of Ag vacancies that can vehicle self-diffusion of Ag+ ions in this material. The calculated activation energy for the diffusion of O2‒ ions (1.07 eV) is significantly lower than that calculated for the diffusion of Ag+ ions (2.44 eV). The prominent isovalent dopants on the Ag and the Nb sites are found to be Na+ and Ta5+ respectively. Doping of Ge on the Nb site can facilitate the formation of oxygen vacancies required for the oxygen diffusion. Additional Ag vacancies required for the self-diffusion of silver can be introduced by doping of Ca on the Ag site. Electronic structures of non-defective and defective AgNbO3 are discussed using density functional theory calculations.