Abstract:TiO₂-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl₄ in the presence of La³⁺. After calcination at 900 ℃ for 1 h, the resultant TiO₂ nanoparticles on the sericite surfaces exist in anatase phase. The light scattering indexes of the TiO₂-coated lamellar sericite powders are dozens of times higher than those of the naked lamellar sericite powders, varying with different contents of La³⁺. The presence of La³⁺ in the deposition solution is beneficial to the formation of the small-sized anatase TiO₂ nanoparticles. The presence of La³⁺ also favors the formation of the dense and uniform island-like TiO₂ coating layers in a large range of the mass ratio of TiO₂ to sericite from 5% to 20%. XPS analysis shows that when La³⁺ is absent in the reaction solution, TiO₂ coating layers anchor on the sericite surface via Ti—O—Si and Ti—O—Al bonds. The presence of La³⁺ causes the formation of Si—O—La and Al—O—La bonds on the sericite surface and Ti—O—La bond on the surface of TiO₂ coating layers.

Key words: lamellar sericite; TiO₂ coating; lanthanum