Ferroelectric Bi₄Ti₃O₁₂ and Bi _4-x la _x Ti₃O₁₂ ceramics prepared by a new sol-gel route

Ceramics of bismuth titanate, Bi₄Ti₃O₁₂ (BIT) and the La-doped series, Bi_4-x La _x Ti ₃O₁₂ (xBLT) with x∈=∈0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, and 0.75, have been synthesized by a new sol-gel process based on ethylene glycol. La-doping is found to reduce the temperature of the formation of pure Bi-layer-structured phase from 600 °C in BIT and low La-doped xBLT (x∈=∈0.1-0.3) to 500 °C in high La-doped xBLT (x∈=∈0.4- 0.75). Increasing the La-content in the xBLT ceramics decreases the contribution of the space charge polarization to the apparent dielectric permittivity. The ceramics of xBLT prepared by this sol-gel route exhibit improved dielectric properties, with a higher room temperature dielectric constant and lower losses up to high temperatures.