Facile Morphological Modification of Ba5Nb4O15 Crystals Using Chloride Flux and in Situ Growth Investigation

Abstract

The cation-deficient layered perovskite oxide Ba5Nb4O15 is one of the functional materials that exhibits a microwave-responsive dielectric property and an ultraviolet-active photocatalytic property. Although systematic control of the morphology of Ba5Nb4O15 is beneficial for improving these properties, synthesized Ba5Nb4O15 usually has a plate-like shape owing to its crystal structure, with a particle size less than 5 μm. For systematic morphological control of Ba5Nb4O15, the crystal growth was studied by using a chloride-based flux method. Idiomorphic plate-like Ba5Nb4O15 crystals up to 50 μm in size and polyhedron ones ∼10 μm in size were obtained using a BaCl2 flux by changing the solute concentration to 5–20 mol % and 50 mol %, respectively. The growth of the Ba5Nb4O15 crystals was investigated by thermogravimetric and differential thermal analysis and in situ X-ray diffraction analysis. These analyses revealed the flux-growth manner of Ba5Nb4O15 as follows: (I) Ba5Nb4O15 was formed by a solid-state r...