Barium Titanate Torus‐Like Particles: Low‐Temperature Synthesis and Formation Mechanism

Abstract This work aims to clarify the mechanism of formation of torus‐like barium titanate (BaTiO 3 ) particles with a view to evaluating the properties of these hollow perovskite oxide crystals. Crystalline BaTiO 3 powders have been synthesized by hydrothermal treatment of titanium‐based nanotubes and barium chloride in alkaline media at 90, 110 and 200 °C for various reaction times. The possibility of obtaining hollow barium titanate particles at intermediate stages of crystallization by a low‐temperature template‐free process is demonstrated. The formation of a hollow in the centre of the particles is attributed to the Kirkendall effect associated with the different diffusion rates of Ba 2+ and Ti 4+ hydrothermal species through the (010) crystallographic plane of the BaTiO 3 lattice and with the formation of vacancies.