Sodium niobate based hierarchical 3D perovskite nanoparticle clusters.

We report a microwave assisted synthesis of NaNbO3 perovskite mesocrystals with a hierarchical morphology formed by the self-assembly of nanoparticles in particle clusters. The synthesis method combines non-aqueous sol-gel synthesis and microwave heating in a single step process that allows us to isolate crystalline single phase NaNbO3 in few minutes. A detailed investigation of the effect of the reaction temperature on the crystallinity and morphology of the product was conducted. The synthesis stabilizes the unusual orthorhombic phase Pmma, a property that can be ascribed to the crystal size (24 nm). TEM and SAED analyses show that the hierarchical polycrystalline particles behave as single crystals, a feature related to a non-classical crystallization mechanism. Moreover, the optical bandgap of this NaNbO3 phase was estimated for the first time. The results suggest the potential of this synthetic procedure for the fast production of high quality tertiary oxide nanocrystals.