Evolution of rutile TiO2 coating layers on lamellar sericite surface induced by Sn4+ and the pigmentary properties

Rutile TiO2-coated sericite powders were prepared by the chemical deposition method starting from lamellar sericite and TiCl4 in the presence of Sn4+. After calcination at 850 °C for 4 h, TiO2 nanolayers in rutile phase were formed on the sericite surfaces. The presence of Sn4+ induced the phase transformation of amorphous to rutile TiO2, giving the formation of TiO2 nanolayers composed of small-sized rutile TiO2 nanoparticles. XPS analysis shows that Sn4+ cations were anchored at the sericite surfaces by formation of Al–O–Sn and Si–O–Sn bonds, and the aluminum and silicon sites on the sericite surfaces were dominantly occupied by Sn4+ cations. TiO2 coating layers were subsequently anchored at the sericite surfaces via Ti–O–Sn bonds. The TiO2-coated sericite powders had higher light scattering indexes than the naked sericite powders. The brightness, whiteness, and light scattering index of the rutile TiO2-coated sericite powders were slightly higher than those of the anatase TiO2-coated sericite powders.