1. Mineral forms of titanium dioxide

In nature, titanium dioxide crystallizes in three main forms: anatase, rutile and brookite. Rutile and anatase are the main forms used in industrial applications. The brookite form could be of interest due to its good dielectric properties, but its synthesis remains difficult to master. In addition to these three structural forms, the minerals columbite, baddelyite and cotunnite may also appear. The main physical properties of the rutile and anatase crystal forms are described in Table 1 .