Effects of Excess Bismuth on Structure and Properties of SrBi4 Ti4 O15 Ceramics

SrBi4Ti4O15(SBTi) ferroelectric ceramics with excess bismuth (Bi) contents ranging from 0% to 25% were prepared by sol-gel method. Effects of excess Bi contents on the microstructure and electric properties were investigated. The SBTi ceramics sample with 10% of excess Bi showed a pure layered perovskite structure with enhancee electric properties. Its Curie temperature, relative dielectric constant, dielectric loss, remanent polarization (2Pr) and coercive field (2Ec) were 518 °C, 248, 0.0021, 20.5 μC·cm-2and 87.8 kV · cm-1, respectively. The degraded electric properties observed in SBTi ceramics with excess bismuth contents lower or higher than 10% could be attributed to the structure defects and the formation of a second phase. © 2007 The Chinese Society of Rare Earths.