Light-scattering efficiency of white pigments: an analysis of model core - shell pigments vs. optimized rutile {TiO2}

The light-scattering efficiency of a white pigment is strongly dependent on its refractive index and particle size. Rutile TiO 2 is an effective opacifier because of its high refractive index. Its efficiency can be further optimized by generating narrow particle size distributions near the optimum diameter. Recently, an alternative core-shell pigment was proposed as a means of increasing the light-scattering efficiency of TiO 2 . The proposed hybrid pigment would be prepared by coating a shell of titania on spherical silica particles or some other low-refractive-index material. Theoretical calculations of the light-scattering efficiencies of these core-shell particles and solid TiO 2 particles show that core-shell particles are substantially less efficient light-scattering materials than pure rutile, especially in the domain of titania coating thickness that can be realistically applied to a core material. Application : a theoretical comparison of the light-scattering efficiency of titania-coated silica spheres and pure rutile. Results demonstrate that the coated spheres are substantially less efficient than pure rutile.