Bismuth titanate was synthesized under hydrothermal conditions from an amorphous Bi-Ti precursor gel. The gel was reacted under hydrothermal conditions at 160 and 180 °C to form crystalline bismuth titanate. The gel crystallization kinetics increased with temperature, resulting in 100% crystalline bismuth titanate in 12 h at 180 °C. WDS data indicated that sodium was incorporated into bismuth titanate during processing. TEM micrographs showed that the gel particles decomposed into 100-200 ran crystalline bismuth titanate particles during hydrothermal processing. The effect of sodium on the properties of bismuth titanate was investigated by examining Bi_4Ti_3O_(12) powders doped with 1-3 atomic % sodium. Sodium doping caused a structural transformation from the Bi4Ti3012 to the Na_(0.5)Bi_(8.5)Ti_7O_(27) phase on heating to 1100 C in air. The transformation proceeded through the Naa5BiS5Ti.,O27 configuration that has a structure with alternating two and three perovskite-like blocks interleaved with Bi_2O_2~(2+)layers. Doping with sodium decreased the electrical conductivity of bismuth titanate.
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