2018 Volume 126 Issue 12 Pages 997-1004
The Soret effect or thermodiffusion is temperature-gradient-driven diffusion in a multicomponent system. A physical model to accurately predict the Soret coefficient of oxide melts has not yet been proposed. Here, for the first time, we report a quantitative comparison between experiment and theory concerning the Soret coefficient in binary glass-forming oxide melts. We measured the Soret coefficient of 11Na2O–89B2O3 (mol %) after 90- and 180-h heat treatment under a temperature gradient near 1200 K and estimated the Soret coefficient for the steady state. We used a vertical furnace to reduce the effect of natural convection on the Soret effect by heating the sample from the top side. The Soret coefficient estimated for the steady state near 1200 K was 5.12 × 10−3 K−1, whereas that obtained by the adjusted Kempers model, in which we adjusted the original Kempers thermodynamic model for binary oxide melts, was 6.09 × 10−3 K−1. The sign and order of magnitude were consistent, which suggests that the adjusted Kempers model is a promising model to explain the Soret effect and that the equilibrium thermodynamic parameters of partial molar volume, partial molar enthalpy, and chemical potential are important factors in the phenomenon.