Template-Free and Scalable Synthesis of Core−Shell and Hollow BaTiO₃ Particles: Using Molten Hydrated Salt as a Solvent

Molten hydrated salt was used, for the first time, as a new kind of solvent to explore the synthesis of complex oxide nanomaterials. Employing Ba(OH) 2 ·8H 2 O as the solvent, and rutile TiO 2 as the reactant, core−shell and hollow nanoparticles of perovskite-type BaTiO 3 were successfully fabricated under sealed conditions at 180 °C. No other additive was introduced into the reaction system. The effect of various reaction conditions on the morphology and size of the products was investigated. At high TiO 2 dosage, core−shell BaTiO 3 particles were the dominant products with their sizes between 400 and 800 nm, whereas relatively low TiO 2 dosage favored the formation of hollow BaTiO 3 particles less than 250 nm. The formation process of the products was investigated, and can be attributed to an Ostwald ripening induced hollowing mechanism. Because of its simplicity and scalability, the molten hydrated salt method may open up a promising route for the synthesis of complex oxide micro/nanomaterials for practical applications.