Diffusivities of polyvalent elements in glass melts

Self-diffusion coefficients of polyvalent elements have been measured as a function of temperature in silicate melts of different compositions using square-wave voltammetry, a fast potentiostatic pulse method. In the temperature range of 700 to 1500 degrees C, a linear correlation between log(D) and 1/T is observed for all polyvalent elements and glass melt compositions. The self-diffusion coefficients are highest for Ag+ and up to six orders of magnitude lower for Cr6+. Self-diffusion coefficients of polyvalent ions with valencies two to four lie between these limits. The self-diffusion coefficients also strongly depend on the melt composition. In melts possessing higher alkali content and hence lower viscosity, higher diffusion coefficients are observed.