Nanocrystalline titanate powders: Synthesis and mechanisms of perovskite particles formation

Abstract

Nanocrystalline titanate (SrTiO 3 , PbTiO 3 and La 2/3 TiO 3 ) powders were synthesized by solgel and hydrothermal method in a two-step process, first by controlled hydrolysis of titanium-butoxide with distilled water, and then by further reaction of the formed amorphous titanium hydroxide gel particles with Sr 2+ , Pb 2+ or La 3+ ions, carried out under different reaction conditions. Mechanisms and conditions for the formation of crystalline titanate nanoparticles in different systems were investigated. It is found that: (1) traces of strontium titanate nanoparticles with crystalline perovskite structure appear already at 20°C, but a complete crystalline nanopowder is synthesized at 80°C, (2) crystalline perovskite particles in PbTiO 3 and La 2/3 TiO 3 system can be obtained only under the hydrothermal conditions at higher temperatures, and (3) the PbTiO 3 powders synthesized under the hydrothermal conditions are highly agglomerated and depending on processing conditions can have different morphology starting from spherical agglomerates, to platelet-like structure or even a complex structures involving titanate particles covered with one-dimensional nanostructured elements.