Electrical conductivity and dielectric dispersion phenomena of concentrated TiO2 suspensions

The complex conductivity of concentrated TiO2 suspensions (up to 50 vol%) w as measured over a large frequency range (1 MHz-1.8 GHz), as a function of grain volume content. These measurements highlight relaxation phenomena in the intermediate frequency range, which are associated with the dispersed p owder. These phenomena were previously noted in O'Brien's theoretical devel opments. A quantitative data analysis was made, in terms of time constant d istribution, using the CONTIN software, from Provencher. As a result, a com plex process is highlighted, including two main mechanisms in different ran ges of time constants. Particularly, we showed good agreement between the h igher frequency mechanism and the O'Brien theory. From Dukhin's lambda rati os, which are ratios of grain surface to bulk electrolyte conductances, we calculated the electrolyte conductivity as a function of powder concentrati ons. At higher powder concentrations, these values are different from those measured with centrifuged liquids. (C) 2000 Academic Press.