Localized crystallization: a chemical transformation of Nb2O5 rod-like arrays into ordered niobate arrays

A key limitation for various applications of niobium (Nb)-containing thin films is the lack of remarkably economic, simple and versatile methods for effectively generating large-scale ordered arrays. We used well-aligned Nb2O5 rod-like arrays as a sacrificial precursor to demonstrate how a wide range of niobate arrays can be obtained through a localized crystallization process. NaNb3O8 microtube arrays, NaNbO3 microrod arrays, and new-phase K2Nb2O6 microtube arrays were selectively crystallized by dynamically controllable interfacial reactions between alkali solution and solid Nb2O5 template. The current low-temperature hydrothermal synthesis was proved straightforward and technically flexible for the shape-and structure-control of oxide surface architectures. Most importantly, the chemical synthesis of highly ordered Nb-based binary and ternary oxide arrays provided a much deeper understanding of crystallization behaviour during a sacrificial-templating process and also a successful chemical strategy for crystallizing more alkali or alkaline earth metal complex oxide films with great technological importance.