Ferroelectric hollow particles obtained by solid-state reaction

Abstract

Hollow particles of barium titanate were obtained by a two-stepprocess combining colloidal chemistry and solid-state reaction.BaCO3 crystals(size ≈1 µm) suspended in a peroxy-Ti(IV) aqueous solution were coated with an amorphousTiO2 shell using a precipitation process. Calcination of theBaCO3@TiO2 core–shell particles at700 °C resulted in the formationof BaTiO3 hollow particles(shell thickness of ≈70 nm) which retain the morphology of theBaCO3 crystals. Formation of the cavity occurs because out-diffusion of the core phase is much fasterthan in-diffusion of the shell material. X-ray diffraction (XRD) and Raman spectroscopyindicate that the hollow particles possess a tetragonal ferroelectric structure with axial ratioc/a = 1.005. Piezoresponse force microscopy has shown strong piezoactivity and180° ferroelectric domains. The process described provides a general route to fabricate hollowferroelectric structures of several compounds.