Point-defect chemistry on the polarization behavior of niobium doped bismuth titanate

The present work shows the defect chemistry at room temperature of Bi₄Ti₃O₁₂, emphasizing the effect of point defects on the ferroelectric properties. Electrical measurements of conductivity, dielectric permittivity and dielectric loss as well as structural characterization and Electron Spin Resonance (ESR) were used to deduce the existence of different point defects. Pure and Niobium doped bismuth titanate ceramic were prepared by a conventional solid state reaction technique. Rietveld refinement analysis suggested that niobium atoms occupy the titanium lattice sites and the presence of bismuth vacancies. Electron Spin Resonance measurements showed signals that are associated to iron impurities. The present communication supports the models of compensation mechanisms dominated by free electrons and bismuth vacancies.