Refractive index rutile titania

Many methods have also been demonstrated to process materials other than polystyrene and silica into spherical colloids as monodisperse samples. For example, a new method was recently reported that allowed for the generation of titania spherical colloids with uniform diameters controllable in the range of 200 to 500 nm.66 Titania is a semiconductor and has a much higher refractive index (2.6 for anatase and 2.9 for rutile) when... 

Fig. 8a-c. Electron microscopy images of hollow titania spheres prepared by calcination of PS spheres coated with seven layer pairs of TALH and PDADMAC at a,b 450°C c 950°C. a and b are hollow anatase (refractive index, n 2.5) titania spheres and c hollow rutile (n 2.6-2.9) macroporous titania spheres. (Adapted from [65], by permission of Wiley-VCH)... 

Titania most often appears in the form of one of two predominant crystallographic polymorphs, rutile and anatase. At least seven other distinct phases have been characterized by x-ray diffraction [3], but none are sufficiently commonplace to play a role in pigmentation using titanias. Rutile possesses a higher refractive index than anatase. It is also inherently considerably less photoactive than anatase. For these reasons, rutile has become the predominant polymorph of titania for pigmentary uses in polymers. 

Closely related to the salt infiltration method discussed above is the utilization of metal alkoxide precursors in a sol-gel process to fill the interstitial sites in an opal template. The template is first infiltrated with an alkoxide (neat or as solution), then the hydrolysis and condensation reaction following the infiltration transforms the alkoxides into an extended network of the corresponding metal oxide. By this method Ti02 networks besides other oxides were initially prepared with a strong focus on their optical properties as photonic crystals [30,50]. For this purpose a high refractive index material is desired, which would be the rutile modification of titania with the highest refractive index. Nevertheless, the sol-gel procedure provides an amorphous or anatase modification with lower refractive index. By calcination of the anatase... 

Titanium dioxide, rutile n. Ti02- Pigment white 6 (77891). A high-opacity, bright white pigment, non-chalking type, used as a prime pigment in paints, rubber, plastics. Prepared from the mineral, ihnenite, or rutile ore. Density, 3.9-4.2g/cm (33-35 lb/ gal) O.A., 16 8 particle size, 0.2-0.3 pm, refractive index, 2.76. Syn titania. 

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