Lanthanum-doped Bi₄Ti₃O₁₂ ceramics prepared by high-pressure technique

We present an effective way in this paper to increase the density of lanthanum doped bismuth titanate ceramics, Bi_4-xLa_xTi₃O₁₂ (BLT), thereby significantly improving the performance of the BLT ceramics. Dense BLT ceramicses, Bi_4-xLa_xTi₃O₁₂ (x = 0.25, 0.5, 0.75, 1.0), are prepared by using nanocrystalline powders fabricated by sol–gel method and high-pressure technique. The microstructures of the BLT ceramicses prepared separately by conventional-pressure and high-pressure techniques are investigated by using x-ray diffraction and transmission electron microscope. The influence of La-doping on the densification of bismuth titanate ceramics is investigated. The experimental results indicate that the phase compositions of all samples with various lanthanum dopings sintered at 900℃ possess layer-structure of Bi₄Ti₃O₁₂. The green compacts are pressed under 2.5 GPa, 3.0 GPa, 3.5 GPa and 4.0 GPa, separately. It is found that the density of BLT ceramics is significantly increased due to the decreasing of porosity in the green compacts by high-pressure process.