Effect of Nb-doping on the microstructure and dielectric properties of (Ba0.80Sr0.20)TiO3 ceramics

The effects of cationic substitution of niobium for titanium in (Ba0.80Sr0.20)TiO3 composition on the structural and dielectric properties as well as on the electrical conductivity and Seebeck effect were investigated. X-ray diffraction study at room temperature and the real (ɛ′) and imaginary (ɛ″) parts of permittivity measurements in a wide temperature (from −200 to 450 °C) and frequency (0.1–100 kHz) range were carried out. The analysis of the results of electric conductivity and Seebeck coefficient leads to the conclusion that Nb5+ ions, reducing the conductivity of about two orders, are playing role of donors. The correlation between electric characteristics and niobium concentration was confirmed and the evolution from normal ferroelectrics with diffuse phase transition to relaxor ferroelectrics has been found.