Nanocrystalline oxide (Y2O3, Dy2O3, ZrO2, NiO) coatings on BaTiO3 submicron particles by precipitation

Nanocoatings (5-20 nm) of different compounds on fine BaTiO3 particles were obtained by means of precipitation processes. Homogeneous and smooth shells of Y(OH)CO3 and Dy(OH)CO3 were grown from nitrate solutions in the presence of urea. An irregular coating consisting of zirconia nanoparticles was produced from zirconyl nitrate solution using ammonia as a precipitating agent after adsorption of a polymeric polyelectrolyte on the BaTiO3 surface. Composite particles with a peculiar morphology were obtained by inducing heterogeneous nucleation and growth of Ni(OH)2 lamellae on the BaTiO3 surface. The different shells can be transformed in a nanocrystalline coating of the corresponding oxide (Y2O3, Dy2O3, ZrO2, NiO) by calcination at moderate temperatures (400-700 °C). The overall results indicate that precipitation from solution represents a versatile process to grow a second-phase layer on the surface of BaTiO3 particles. This approach can be used as an alternative to mechanical wet mixing for controlled doping of ferroelectric materials and for the fabrication of composite materials with specific geometry of the two-phase assembly.