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An isothermal hydrothermal reaction scheme has been developed to
produce pure, ultrafine crystalline lanthanum titanate from lanthanum
nitrate-titanium tetrabutyloxide-water-alcohol. It was found that the pH of
the hydrothermal reaction medium and the initial [La]/[Ti] (molar ratio) were
critical factors in forming stoichiometric La2/3TiO3. By varying the pH of
the reaction medium, different end products could be obtained. With
[La]/[Ti]=0.5, the as-prepared La2/3TiO3 was in the cubic perovskite phase,
and the structure did not change when the temperature was increased from room
temperature to as high as 1000 °C. The optimum synthesis conditions including
the ratio of [La]/[Ti], the concentration of NaOH and the lowest synthesis
temperature were investigated. Under hydrothermal conditions, the La2O3-3TiO2
system can tolerate the solid solubility of TiO2.
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