Crystallization of NaNbO3 microcubes by a solution-phase ion exchange route

Sodium niobate (NaNbO3) microcrystals were crystallized by a technically flexible ion exchange method in solution phase. A potassium niobate hollow sphere (KNHS) precursor was first grown via a hydrothermal route, the metastable compound is chemically active in NaOH solution, leading to the crystallization of NaNbO3 microcrystals by a spontaneous ion exchange and recrystallization process. The crucial influences of ion exchange duration, NaOH concentration, surfactant, and reaction medium (water, ethylene glycol/water, ethylenediamine/water) on both the morphology and crystal phase of the NaNbO3 microcrystals have also been established. This current chemical route provides an extremely simple, mild, and effective recipe to crystallize NaNbO3, which could possibly be expanded to more niobate crystals with well controlled chemical compositions, structures, and particle morphologies.