AN157 Refractive Index Selection

Laser diffraction is one of the most widely used methods for particle size analysis of micron and submicron size powders and dispersions. It is quick and easy and provides very consistent, repeatable information. Since these instruments use scattered light intensity to determine particle size, knowledge of the optical properties, specifically the complex refractive index of the material being analyzed is required. While the optical properties of the individual components of a mixture are readily available, what happens when we want to determine the size distribution of a mixture? This note briefly describes an approach that allows determination of a suitable index of a typical ceramic mixture using knowledge of the materials and statistical goodness-of-fit parameters provided by the analyzer software.