Temperature dependent conductivity of Bi₄Ti₃O₁₂ ceramics induced by Sr dopants

Bi₄Ti₃O₁₂ is an important lead-free ferroelectric material. Doping modification of Bi₄Ti₃O₁₂ has attracted great attention to improving its performances. In this work, the effect of Sr dopants on the microstructure, dielectric, and conductivity of Bi₄Ti₃O₁₂ ceramic was investigated by XRD, SEM, and AC impedance spectroscopy. Substitution of 1 at% Sr for Bi decreased the grain size, suppressed the dielectric dispersion of Bi₄Ti₃O₁₂ ceramic at room temperature, and resulted in different effects on the conductivity of grains and grain boundaries. The conductivity of grains in Bi₄Ti₃O₁₂ ceramic was increased by the small amount of Sr dopants in the whole experimental temperature range. While the grain boundaries of 1 at% Sr-doped Bi₄Ti₃O₁₂ exhibited lower conductivity than pure Bi₄Ti₃O₁₂ below ~380 °C and higher conductivity above ~380 °C. The experimental phenomena were interpreted in term of compensating defects for Sr dopants.