Controlled growth of silica shell on Ba0.6Sr0.4TiO3 nanoparticles used as precursors of ferroelectric composites

A method based on a seeded growth process was developed to coat ferroelectric nanoparticles with a dielectric silica shell. This method, applied to size-polydispersed (Ba0.6Sr0.4)TiO3 particles (BST, mean diameter 150 nm), allows the control of the silica shell thickness from 2 to 80 nm with an accuracy of 1-2 nm. The morphology and surface physical chemistry of the core-shell were studied by transmission electron microscopy, photon correlation spectroscopy, and zeta potential measurements. A size-sorting procedure consisting of several cycles of centrifugation was optimized to extract the BST@silica nanoparticles of the required size for dielectric properties tuning. Upon sinted ng, dielectric measurements showed that the ferroelectric transition was maintained in the dense nanocomposites.