Possibility of ferroelectric bismuth and nitrogen co-doped barium titanate

Abstract

The possibility of bismuth (Bi) and nitrogen (N) co-doped barium titanate (BaTiO₃) as a ferroelectric material was investigated by calculation and experiment. From first principles calculations, it was found that Bi and N co-doped BaTiO₃ has a higher spontaneous polarization than undoped BaTiO₃ since dopant Bi and N ions contribute to the enhancement of covalent interactions between cations and anions. Because it was revealed that the ferroelectricity of BaTiO₃ can be improved by co-doping of Bi and N, we demonstrated the synthesis of (Ba,Bi)Ti(O,N)₃. Single phase oxynitride (Ba,Bi)Ti(O,N)₃ powder was fabricated by annealing (Ba,Bi)TiO₃ in NH₃ gas. The tetragonal distortion of (Ba,Bi)Ti(O,N)₃ was smaller than that of BaTiO₃, which may be due to A-site and O-site vacancies in the perovskite lattice introduced during NH₃ annealing.