Preparation of Plate-Like Sodium Niobate Particles by Hydrothermal Method.

Sodium niobate NaNbO₃ hydrate ( NN-hydrate) particles with a plate-like morphology were prepared at 140°C for 2 h in 12 mol/L of NaOH by the hydrothermal method. Bar-like Na₈Nb₆O₁₉·13H₂O particles were synthesized at as low as 100°C for 2 h. This work demonstrates that by carefully optimizing the reaction condition, we can selectively fabricate niobate structures, including the bar-like, plate-like, fibers and cube particles through a direct reaction between NaOH solution and Nb₂ O₅. It was found that Nb₆ O₁₉⁸⁻ formed was an important premise for formation of the NN-hydrate, and lower [ OH^-] was not favorable in preparing the NN-hydrate as there was an optimum [ OH⁻]. Through researching effects of the reaction temperature, time, concentration of NaOH, and content of Nb₂ O₅ on the NN-hydrate structure and evolution, the formation mechanism from solid reactants to the intermediate were investigated. After calcining at 800°C, the synthesized NN-hydrate particles made a phase almost transform to the perovskite NaNbO₃, and the morphology of these calcined particles was still plate-like. [ABSTRACT FROM AUTHOR]