Titanium dioxide pigment particles with doped, dense SiO2 skin and methods for their manufacture

A method for manufacturing TiO2 pigment particles whose surface is coated with a dense SiO2 skin doped with at least one doping element, comprising the steps:

• a) reacting titanium tetrachloride with an aluminium halide and a gas containing oxygen in a gas phase reactor at a temperature above 1,000° C., thereby creating a gas stream containing TiO2 particles;
• b) contacting the particle containing gas stream with at least two compounds, where a first compound is a silicon oxide precursor compound and a second compound is selected from the group consisting of oxide precursor compounds of Sn, Sb, In, Y, Zn, Mn, Cu, Mo, Cd, Ce, W, Bi and precursor compounds of F as well as mixtures thereof,
• c) cooling the particle stream, thereby creating pigment particles that are coated with a dense SiO2 skin deposited on the TiO2 core particles, the dense SiO2 skin doped with at least one doping element.

Titanium dioxide (TiO2) pigment particles, comprising:

• a) TiO2 core particles;
• b) a dense silicon dioxide (SiO2) skin covering the core, the dense skin produced in a dry process, the dense skin doped with at least one doping element, wherein the at least one doping element either reduces the density of states near the band edge or creates additional states in the band gap of the material of the dense skin, excluding doping elements selected from the group consisting of Al, B, Ge, Mg, Nb, P, and Zr.