Effect of co-substitution of nitrogen and fluorine in BaTiO3 on ferroelectricity and other properties.

摘要: BaTiO3, with both nitrogen and fluorine substituted for oxygen, has been prepared the properties of doped material composition BaTiO2.8N0.1F0.1 have studied. The color sample changes to light green on doping, accompanying a broad visible absorption band its edge at 2.5?eV. first-order ferroelectric transition doping along decrease in dielectric constant. We examined local structure, electronic structure polar lattice dynamical N F co-substituted BaTiO3 using first-principles density functional theory-based calculations derived mechanism diffuse observed here peak temperature-dependent response. calculated Born charges clearly reveal strong disparity interaction N, O Ti: being most ferro-active, highly anomalous charge, least active, an almost nominal charge. This originates from which top-most valence is constituted 2p states while lie deep energy band, resulting short covalent Ti?N long ionic Ti?F bonds. Disorder these hetero ferro-active anions leads relaxor-like phase reduction polarization. Calculations confirm 0.65?eV bandgap indirect direct type.